阅读说明：本技术 具备非圆柱形平台的垂直腔面发射激光器及其制备方法 (Vertical cavity surface emitting laser with non-cylindrical platform and preparation method thereof ) 是由 方照诒 于 2020-09-02 设计创作，主要内容包括：本发明提供具备非圆柱形平台的垂直腔面发射激光器及其制备方法,所述激光器包括衬底、位于所述衬底之上的第一镜层、位于所述第一镜层之上的活化层和位于所述活化层之上的第二镜层,所述第二镜层、所述活化层和靠近所述活化层的部分所述第一镜层经过蚀刻之后形成非圆柱形主动区平台。本发明综合考虑了晶面类型以及主动区平台不同方向对氧化速度的影响,针对不同的晶面类型,对常用的圆柱形主动区平台的形状进行改进,进而实现氧化孔径的形状规则化,使其与圆形或正多边形近似,使VCSEL射出的光更加的规则。(The invention provides a vertical cavity surface emitting laser with a non-cylindrical platform and a preparation method thereof, wherein the laser comprises a substrate, a first mirror layer positioned above the substrate, an active layer positioned above the first mirror layer and a second mirror layer positioned above the active layer, and the non-cylindrical active region platform is formed after the second mirror layer, the active layer and part of the first mirror layer close to the active layer are etched. The invention comprehensively considers the influence of crystal face types and different directions of the active region platform on the oxidation speed, improves the shape of the common cylindrical active region platform aiming at different crystal face types, further realizes the shape regularization of the oxidation aperture, and ensures that the oxidation aperture is similar to a circle or a regular polygon, so that the light emitted by the VCSEL is more regular.)

1. The vertical cavity surface emitting laser with the non-cylindrical platform comprises a substrate, a first mirror layer positioned on the substrate, an active layer positioned on the first mirror layer and a second mirror layer positioned on the active layer, wherein the second mirror layer, the active layer and a part of the first mirror layer close to the active layer form an active region platform after being etched, and the active region platform adopts a 112 crystal face, and is characterized in that: and correcting the shape of the active area platform, wherein the shape of the cross section of the active area platform parallel to the substrate after correction is as follows: and after the ellipse is cut by three curves with openings back to the center, the two path directions with the shortest length from the center to the edge of the ellipse correspond to the two path directions with the longest distance from the center of the oxidation aperture to the edge of the oxidation aperture actually formed after the active region platform is oxidized before correction, and the point with the shortest distance from the center of the ellipse on the other curve is positioned on the long axis of the ellipse.

2. A vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 1, wherein: the maximum length of a connecting line from a point on the ellipse to the center of the ellipse cut by the curve is R1-R2, wherein R2 is the shortest distance from the center of an oxide aperture actually formed after the mesa oxidation of the active region before correction to the edge of the oxide aperture approximately parallel to the crystal direction of the main flat side of the substrate, and R1 is the shortest distance from the center of the oxide aperture actually formed after the mesa oxidation of the active region before correction to the other side of the oxide aperture.

3. A vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 2, wherein: the ellipse satisfies the relation:wherein RA is 1/2 of the length of the major axis of the ellipse, RB is 1/2 of the length of the minor axis of the ellipse, theta is the smaller included angle value of two included angles between the two paths with the shortest length from the center to the edge of the ellipse after correction and the minor axis of the ellipse, and R is the radius of the circular cross section of the active region platform before correction.

4. A vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 1, wherein: the three curves do not intersect within the ellipse.

5. A vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 1, wherein: the curve is an arc with the radius R, and the radius R is the radius of the circular cross section of the active area platform before correction.

6. A vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 1, wherein: the curve is a conic curve, a polygonal curve, or a combination thereof.

7. The preparation method of the vertical cavity surface emitting laser with the non-cylindrical platform is characterized by comprising the following steps: for fabricating a vertical cavity surface emitting laser with a non-cylindrical mesa according to any of claims 1 to 6, comprising the steps of:

designing a photomask according to the crystal face type of a wafer, so that the photomask can form a cross-sectional graph of a non-cylindrical active region platform corresponding to the crystal face type on the surface of the wafer, wherein the cross-sectional graph is as defined in any one of claims 1 to 6;

photoetching by using the photomask to form a cross-section pattern of a non-cylindrical active area platform on the upper surface of a wafer;

etching to form a non-cylindrical active region platform, wherein the side wall of the non-cylindrical active region platform exposes the oxidation limiting layer;

and oxidizing the side wall of the non-cylindrical active region platform to form an oxidation aperture.

8. A method of fabricating a vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 7, wherein: before designing a photomask, aiming at the crystal face type of the wafer, carrying out an experiment, firstly setting a cylindrical active region platform with the radius of R in the experiment, forming an experimental condition of a target oxidation aperture with the radius of R after side wall oxidation, and then obtaining the shape, the related direction and the length data of the actually formed oxidation aperture of the cylindrical platform with the radius of R after side wall oxidation by adopting the experimental condition.

9. A method of fabricating a vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 8, wherein: and (3) aiming at the same crystal face type, carrying out multiple experiments, wherein the conditions of each experiment are set to be the same, and taking the average value or the fitting value of the multiple experimental results as the final experimental result of the finally determined crystal face type.

10. A method of fabricating a vertical cavity surface emitting laser having a non-cylindrical mesa as claimed in claim 9, wherein: further comprising the steps of: epitaxial growth of a wafer; preparing an electrode; passivating the side wall of the platform in the active area to form a passivation layer, and arranging a filler.

Technical Field

The invention relates to the field of semiconductors, in particular to a vertical cavity surface emitting laser with a non-cylindrical active region platform and a preparation method thereof.

Background

The VCSEL, known as a vertical cavity surface emitting laser, mostly defines the light exit hole by using an oxidized aperture method during the fabrication process. The main process steps comprise: the wafer epitaxial growth, in the course of the wafer epitaxial growth, first mirror layer and/or second mirror layer close to activating layer have Al with very high composition AlGaAs layer as oxidizing the limit layer; etching the wafer formed by epitaxial growth to form a cylindrical active region platform, wherein the oxidation limiting layer is required to be exposed on the side wall of the active region platform; oxidizing the side wall of the active region platform to form an oxidation aperture, wherein during oxidation, the oxidation is performed along the oxidation limiting layer in a transverse direction, and the oxidized oxidation limiting layer forms Al_xO_yThe layer, while the intermediate unoxidized areas constitute the oxidation aperture, i.e. the light exit aperture and the current injection region of the VCSEL. The shape of the oxide aperture is related to the shape of the VCSEL emitted light.

In the oxidation process, the oxidation law of the oxidation limiting layer has a great relationship with the thickness of the oxidation limiting layer, the content of Al components, the gas flow rate in the oxidation process, the temperature and the like, researchers pay great time and energy to research the influence of the factors on the oxidation law, so that the oxidation aperture has a more regular shape through controlling the factors, and meanwhile, the oxidation limiting layer is improved in various ways to improve the performance of the VCSEL, but few people pay attention to the influence of a crystal face on the oxidation law. The facets (faces) of a crystal are usually expressed by the Miller index method, which is labeled by the reciprocal integer ratio of the reciprocal of the intercept of the facets (or planar lattice) on three crystal axes, as shown in fig. 1a to 1d, and are 4 facets of a cubic system with different Miller indices, wherein fig. 1a shows 100 facets, fig. 1b shows 110 facets, fig. 1c shows 111 facets, and fig. 1d shows 112 facets. The crystal faces with different miller indexes have different atom densities, so that the diffusion speed of the oxidizing gas is different in the oxidation process, the oxidation speed is different, and finally the shape of the oxidation aperture is influenced.

The chinese patent application No. 201910046944.5 discloses a VCSEL chip with a planar structure and a method for manufacturing the same, wherein a main oxidation hole and an auxiliary oxidation hole are formed at one side of an ohmic contact layer of the VCSEL chip, and then a limiting layer is oxidized through the main oxidation hole and the auxiliary oxidation hole to form a limiting layer having a conductive structure layer as a corresponding conductive region and an oxidized structure layer as the remaining portion, so as to limit current through the oxidized structure, thereby allowing current to flow through the conductive structure layer, and making the method for manufacturing the VCSEL chip simpler.

The Chinese patent application with the application number of 201910156150.4 discloses a VCSEL chip with low oxidation stress and a preparation method thereof, wherein an oxidation limiting layer comprises Al which are sequentially stacked_0.9Ga_0.1As epitaxial layer and Al_xGa_1-xAs epitaxial layer and Al_0.98Ga_0.02Epitaxial layer of As, said Al_0.9Ga_0.1An As epitaxial layer disposed adjacent to the active layer, the Al_0.98Ga_0.02The As epitaxial layer is arranged close to the second BDR, and Al is enabled to be arranged through different oxidation rates of the epitaxial layers in the oxidation process_0.9Ga_0.1As epitaxial layer and Al_0.98Ga_0.02The contraction stress of the As epitaxial layer is mutually pulled to enable the stress of the epitaxial layer to be balanced, so that the stress caused by oxidation is reduced, the risks of defect conduction and epitaxial layer shedding are reduced, and the performance of the VCSEL chip is improved.

It can be seen that none of the above prior art has noticed the influence of the crystallographic planes on the oxide pore size. Figures 2 a-2 f show the shape of the oxide aperture of six VCSELs using a cylindrical active region mesa, the shape of the oxide aperture in figures 2 a-2 d is approximately triangular, the shape of the oxide aperture in figure 2e is approximately rectangular, the shape of the oxide aperture in figure 2f is approximately square, it can be seen that the shape of the oxide aperture in figures 2 a-2 f is not approximately circular, only the shape of the oxide aperture in figure 2f is approximately regular polygonal.

Disclosure of Invention

To more clearly explain the technical solution of the present invention, the following description is first made:

the cross section of the active region platform before correction is circular, the radius of the active region platform before correction is R, the side wall of the active region platform before correction is oxidized to form an oxidation aperture, and the target shape of the oxidation aperture is circular with the radius of R. In fact, because the atomic surface densities of the mesas in different directions are different, the diffusion rates of the mesas in different directions are different, and the oxidation rates of the mesas in different directions are different, which finally results in that the oxide aperture formed after the sidewall oxidation of the mesa in the active region with the radius R is not a regular circle. Moreover, the active region platform adopts different crystal planes, and the shape of the finally formed oxide aperture is also different.

The invention provides a vertical cavity surface emitting laser with a non-cylindrical platform and a preparation method thereof, which take the difference of oxidation speeds of different directions of a crystal surface and an active region platform into consideration for a 110 crystal surface, a 111 crystal surface and a 112 crystal surface, correct the shape of a common cylindrical platform, realize the shape regularization of an oxidation aperture, enable the oxidation aperture to be similar to a circle or a regular polygon, and enable light emitted by a VCSEL to be more regular.

A vertical cavity surface emitting laser with a non-cylindrical platform comprises a substrate, a first mirror layer located on the substrate, an active layer located on the first mirror layer and a second mirror layer located on the active layer, wherein the second mirror layer, the active layer and a part close to the active layer are formed into an active region platform after the first mirror layer is etched, the active region platform adopts a 110 crystal face, the shape of the active region platform is corrected, the shape of the cross section of the corrected active region platform parallel to the substrate is similar to the shape of an oxidation aperture actually formed by the active region platform before correction, and the rotation angle is similar to that of the oxidation aperture actually formed by the active region platform before correctionAngle of rotationHas a value range ofAnd m is the number of symmetry axes of the 110 crystal plane.

Preferably, the active region platform adopts a 110 crystal plane, and the shape of the cross section of the active region platform parallel to the substrate satisfies the relation:wherein Ra represents the longest radial length of the cross section of the modified active region platform, Rb represents the shortest radial length of the cross section of the modified active region platform, a represents the shortest radial length of an oxidation aperture actually formed after the oxidation of the active region platform before the modification, b represents the longest radial length of the oxidation aperture actually formed by the active region platform before the modification, and R/R is more than 1 and less than or equal to 3.5.

Preferably, any of the above schemes is that the angleThe value of (1) is the degree of the included angle between the shortest radial direction and the longest radial direction of the oxidation aperture actually formed after the platform of the active region is oxidized before correction.

In any of the above schemes, preferably, the active region platform adopts a 110 crystal plane, and the cross section of the modified active region platform parallel to the substrate is elliptical.

In any of the above schemes, preferably, the active region platform adopts a 110 crystal plane, and the cross section of the modified active region platform parallel to the substrate is an approximate ellipse formed by combining a conical curve and a polygon.

A vertical cavity surface emitting laser with a non-cylindrical platform comprises a substrate, a first mirror layer positioned on the substrate, an active layer positioned on the first mirror layer and a second mirror layer positioned on the active layer, wherein the second mirror layer, the active layer and a part of the first mirror layer close to the active layer form an active region platform after etching, the active region platform adopts a 111 crystal plane, the shape of the active region platform is corrected, and the shape of the corrected active region platform parallel to the cross section of the substrate is as follows: and the three radius directions of the circle with the shortest remaining length after being cut by the curves correspond to the directions of the three paths with the longest distance from the center of the oxidation aperture to the edge of the oxidation aperture actually formed after the platform of the active region is oxidized before correction.

Preferably, the 111 crystal plane is adopted as the active region terrace, the radius of the cut circle is R, the longest length of the radius of the curve cut circle is Rc-Rs, wherein Rc is the longest distance from the center of the actually formed oxide aperture to the edge of the oxide aperture after the oxidation of the active region terrace before the correction, and Rs is the shortest distance from the center of the actually formed oxide aperture to the edge of the oxide aperture after the oxidation of the active region terrace before the correction.

In any of the above schemes, preferably, the active region platform adopts a 111 crystal plane, and the three curves do not intersect in the circle.

In any of the above schemes, preferably, the active region platform adopts a 111 crystal plane, and the curve is an arc with a radius of R.

In any of the above schemes, preferably, the active region platform adopts a 111 crystal plane, and the curve is a conic curve, a polygonal curve or a combination thereof.

A vertical cavity surface emitting laser with a non-cylindrical platform comprises a substrate, a first mirror layer positioned on the substrate, an active layer positioned on the first mirror layer and a second mirror layer positioned on the active layer, wherein the second mirror layer, the active layer and a part of the first mirror layer close to the active layer form an active region platform after etching, the active region platform adopts a 112 crystal face, the shape of the active region platform is corrected, and the shape of the corrected active region platform parallel to the cross section of the substrate is as follows: and after the ellipse is cut by three curves with openings back to the center, the two path directions with the shortest length from the center to the edge of the ellipse correspond to the two path directions with the longest distance from the center of the oxidation aperture to the edge of the oxidation aperture actually formed after the active region platform is oxidized before correction, and the point with the shortest distance from the center of the ellipse on the other curve is positioned on the long axis of the ellipse.

Preferably, the active region platform adopts a 112 crystal plane, and the maximum length of a connecting line from a point on the ellipse to the center of the ellipse cut by the curve is R1-R2, wherein R2 is the shortest distance from the center of an oxide aperture actually formed after the oxidation of the active region platform to the edge of the oxide aperture approximately parallel to the crystal direction of the main flat side of the substrate before the correction, and R1 is the shortest distance from the center of the oxide aperture actually formed after the oxidation of the active region platform to the other side of the oxide aperture before the correction.

In any of the above schemes, preferably, the active region platform adopts a 112 crystal plane, and the ellipse satisfies the relation:wherein RA is 1/2 of the length of the major axis of the ellipse, RB is 1/2 of the length of the minor axis of the ellipse, and theta is the smaller included angle value of two included angles between the minor axis of the ellipse and two paths with the shortest length from the center to the edge of the ellipse after correction.

In any of the above solutions, it is preferable that the active region platform adopts a 112 crystal plane, and the three curves do not intersect in the ellipse.

In any of the above schemes, preferably, the active region platform adopts a 112 crystal plane, and the curve is an arc with a radius R.

In any of the above solutions, it is preferable that the active region platform adopts a 112 crystal plane, and the curve is a conic curve, a polygonal curve, or a combination thereof.

A method for preparing a vertical cavity surface emitting laser with a non-cylindrical platform is used for manufacturing the vertical cavity surface emitting laser with the non-cylindrical platform and comprises the following steps:

designing a photomask according to the crystal face type of the wafer, so that a cross section pattern of a non-cylindrical active region platform corresponding to the crystal face type can be formed on the surface of the wafer;

photoetching by using the photomask to form a cross-section pattern of a non-cylindrical active area platform on the upper surface of a wafer;

etching to form a non-cylindrical active region platform, wherein the side wall of the non-cylindrical active region platform exposes the oxidation limiting layer;

and oxidizing the side wall of the non-cylindrical active region platform to form an oxidation aperture.

Preferably, before designing the photomask, an experiment is performed on the crystal plane type of the wafer, in the experiment, a cylindrical active region platform with a radius of R is firstly set, an experimental condition of a target oxidation aperture with a radius of R is formed after sidewall oxidation, and then the experimental condition is adopted to obtain the shape, the related direction and the length data of the actually formed oxidation aperture after the cylindrical platform with the radius of R is subjected to sidewall oxidation.

In any of the above embodiments, preferably, multiple experiments are performed on the same crystal plane type, the conditions of each experiment are set to be the same, and the average value or the fitting value of the multiple experiment results is taken as the final experiment result of the finally determined crystal plane type.

Preferably, in any of the above embodiments, the preparation method further comprises the steps of: epitaxial growth of a wafer; preparing an electrode; passivating the side wall of the platform in the active area to form a passivation layer, and arranging a filler.

According to the vertical cavity surface emitting laser with the non-cylindrical platform and the preparation method thereof, aiming at the 110 crystal plane, the 111 crystal plane and the 112 crystal plane, the difference of the oxidation speeds of the crystal plane and the active region platform in different directions is considered, the shape of the common cylindrical platform is corrected, the path needing to be oxidized in the direction with the fastest oxidation speed of the oxidation limiting layer is the longest, and/or the path needing to be oxidized in the direction with the slowest oxidation speed is the shortest, so that the shape regularity of the oxidation aperture is realized, the oxidation aperture is approximate to a circular shape or a regular polygon, and the light emitted by the VCSEL is more regular.

Drawings

FIGS. 1a to 1d are schematic diagrams of the crystal planes of 4 different Miller indices of a cubic system.

Figures 2 a-2 f are diagrams of the shape of the oxide aperture of six VCSELs using a cylindrical active region mesa.

Fig. 3 is a schematic diagram of an active region mesa before modification and a target oxidation aperture formed after sidewall oxidation of the active region mesa.

Fig. 4 is a schematic shape diagram of an oxide aperture actually formed after sidewall oxidation of an active region mesa having a radius R using a 110 crystal plane.

Figure 5 is a schematic cross-sectional view of a preferred embodiment of a modified active region platform using the 110 crystal plane in accordance with the present invention.

Fig. 6 is a schematic shape diagram of an oxide aperture actually formed after sidewall oxidation of an active region mesa having a radius R using a 111 crystal plane.

Figure 7 is a schematic cross-sectional view of a preferred embodiment of a modified active region platform using the 111 crystal plane in accordance with the present invention.

Fig. 8 is a schematic view of the shape of an oxide aperture actually formed after sidewall oxidation of an active region mesa having radius R using the 112 crystal plane.

Figure 9 is a schematic cross-sectional view of a preferred embodiment of a modified active region platform using the 112 crystal plane in accordance with the present invention.

FIG. 10 is a schematic flow chart of a preferred embodiment of a method for fabricating a VCSEL with a non-cylindrical mesa in accordance with the present invention.

Fig. 11 a-11 h are graphs of experimental results of oxide aperture formation using non-cylindrical active region mesas of elliptical cross-section.

Detailed Description

For a better understanding of the present invention, reference will now be made in detail to the following examples.

Fig. 3 is a schematic diagram of an active region mesa before modification and a target oxidation aperture formed after sidewall oxidation of the active region mesa. The cross section of the active region platform before correction, which is parallel to the substrate, is circular, the radius of the cross section is R, the side wall of the active region platform before correction is oxidized to form an oxidation aperture, and the target shape of the oxidation aperture is circular with the radius of R. In fact, because the atomic surface densities of the mesas in different directions are different, the diffusion rates of the mesas in different directions are different, and the oxidation rates of the mesas in different directions are different, which finally results in that the oxide aperture formed after the sidewall oxidation of the mesa in the active region with the radius R is not a regular circle. Moreover, the active region platform adopts different crystal planes, and the shape of the finally formed oxide aperture is also different.

Example 1

A vertical cavity surface emitting laser with a non-cylindrical platform comprises a substrate, a first mirror layer located on the substrate, an active layer located on the first mirror layer and a second mirror layer located on the active layer, wherein the substrate is made of GaAs materials, the first mirror layer is an N-type distributed Bragg reflector (N-DBR), the second mirror layer is a P-type distributed Bragg reflector (P-DBR), the active layer is at least one quantum well (MQW), an oxidation limiting layer is arranged at the position, close to the active layer, of the P-DBR, and the oxidation limiting layer is composed of AlGaAs with the Al component higher than 95%. The first mirror layer can also be set to be a P-DBR, and the second mirror layer can be set to be an N-DBR.

The second mirror layer, the active layer and a portion of the first mirror layer adjacent to the active layer are etched to form a non-cylindrical active region mesa, a sidewall of the non-cylindrical active region mesa exposing the oxide confinement layer.

In this embodiment, the active region mesa employs a 110 crystal plane.

Fig. 4 is a schematic diagram showing the shape of an oxidation aperture actually formed after sidewall oxidation by using an active region platform with a radius R of a 110 crystal plane, the actual shape of the oxidation aperture is approximately an ellipse, and an included angle between a major axis of the ellipse and a positive direction of an X axis (i.e., a main flat edge direction of a substrate) is marked as ≦ 1.

For the case that the active region mesa adopts the 110 crystal plane, when determining the shape of the cross section of the modified active region mesa parallel to the substrate, the difference of the oxidation speeds in different directions of the active region mesa should be comprehensively considered, so that the oxidation limiting layer exposed by the non-cylindrical active region mesa formed after etching has the longest oxidation path in the direction with the fastest oxidation speed and/or has the shortest oxidation path in the direction with the slowest oxidation speed, and optimally, after the same oxidation time is passed in each radial direction of the oxidation limiting layer, the unoxidized area of the oxidation limiting layer forms an oxidation aperture which is approximately circular or approximately regular polygonal. It can be seen from fig. 4 that the oxidation rate of the oxidation limiting layer is the slowest in the direction of the major axis of the elliptical oxide aperture, and the oxidation rate of the oxidation limiting layer is the fastest in the direction of the minor axis of the elliptical oxide aperture, so that the cylindrical active region mesa is caused to form the approximately elliptical oxide aperture shown in fig. 4 after sidewall oxidation.

Figure 5 is a schematic cross-sectional view parallel to the substrate of a modified active region mesa employing the 110 crystal plane. The shape of the cross section of the modified active region platform parallel to the substrate is similar to the shape of the actually formed oxide aperture of the active region platform before modification, and is also approximate to an ellipse, and the cross section is rotated by an angleAngle of rotationThe value of (1) is the degree of the included angle between the shortest radial direction and the longest radial direction of the oxidation aperture actually formed after the platform of the active region is oxidized before correction. In the present embodiment, the angleThe value of (2) is 90 degrees, namely after rotation, the long axis direction of the corrected active area platform is the same as the short axis direction of the oxidation aperture actually formed by the active area platform before correction, and the short axis direction of the corrected active area platform is the same as the long axis direction of the oxidation aperture actually formed by the active area platform before correction, so that the path needing oxidation in the direction with the fastest oxidation speed of the corrected oxidation limiting layer is the longest, and the path needing oxidation in the direction with the slowest oxidation speed is the shortest.

Since the shape of the oxide aperture actually formed after the sidewall oxidation of the active region mesa before the modification is not a regular ellipse, and the shape of the oxide aperture desired to be formed after the active region mesa modification is similar to a circle or a regular polygon, the angle is such thatIs gotValue in the rangeThe target can be realized, wherein m is the number of symmetry axes of the 110 crystal face and is 2.

In order to make the shape of the oxide aperture formed after the modification of the active region mesa more regular, the shape of the cross section of the modified active region mesa parallel to the substrate satisfies the relation:wherein Ra represents the longest radial length of the cross section of the modified active region platform, Rb represents the shortest radial length of the cross section of the modified active region platform, a represents the shortest radial length of an oxidation aperture actually formed after the oxidation of the active region platform before the modification, b represents the longest radial length of the oxidation aperture actually formed by the active region platform before the modification, and R/R is more than 1 and less than or equal to 3.5.

Considering the requirements of mask fabrication and etching process in the preparation of VCSEL, the cross section of the modified active region platform parallel to the substrate can be directly designed into an ellipse or designed into an approximate ellipse formed by the combination of a conical curve and a polygon.

If the requirement for the regularization of the shape of the oxide aperture formed by the modified active region platform is not high, or the photomask is required to be simplified, or the etching process is simplified, the modified active region platform can be directly designed into an oval shape; conversely, the shape of the actually formed oxide aperture of the cylindrical active region mesa may be infinitely approximated by a conic section, a polygon, or a combination thereof.

Example 2

Unlike embodiment 1, in this embodiment, the active region mesa of the vcsel having the non-cylindrical mesa employs the 111 plane.

Fig. 6 is a schematic view showing the shape of an oxidation aperture actually formed after oxidation of a sidewall by using an active region mesa having a radius R of a 111 crystal plane, where the actual shape of the oxidation aperture is approximately an equilateral triangle with rounded corners, the distance from the center of the equilateral triangle to three sides is shortest, and the distance from the center of the equilateral triangle to three rounded corners is longest. As can be seen from fig. 6, the direction in which the oxidation speed of the platform in the active region before correction is the direction in which the center of the equilateral triangle is perpendicular to the three sides of the equilateral triangle, and the direction in which the oxidation speed is the slowest is the direction from the center of the equilateral triangle to the vertex angle of each rounding treatment.

Figure 7 is a schematic cross-sectional view parallel to the substrate of a modified active region mesa employing the 111 crystal plane. The shape of the cross section of the modified active region platform parallel to the substrate is as follows: the circle is cut by three curves (shown in gray area in fig. 7) with openings back to the center of the circle, and the three radius directions of the circle with the shortest remaining length after being cut by the curves are consistent with the directions of the three paths with the longest distance from the center of the oxide aperture to the edge of the oxide aperture actually formed after the active region platform is oxidized before correction. The radius of the circle to be cut is R, and the longest length of the radius of the curve cutting circle is Rc-Rs, wherein Rc is the longest distance from the center of the oxide aperture actually formed after the active region terrace is oxidized to the edge of the oxide aperture before the modification, and Rs is the shortest distance from the center of the oxide aperture actually formed after the active region terrace is oxidized to the edge of the oxide aperture before the modification.

In this embodiment, it is preferred that the three curves do not intersect within the circle.

In the present embodiment, it is preferable that the curve is a circular arc having a radius R.

As another embodiment, the curve is a conic curve, a polygonal curve, or a combination thereof.

Example 3

Unlike embodiment 1, in this embodiment, the active region mesa of the vcsel having the non-cylindrical mesa employs the 112 crystal plane.

Fig. 8 is a schematic diagram showing the shape of an oxidation aperture actually formed after sidewall oxidation by using an active region mesa having a radius R of a 112 crystal plane, where the actual shape of the oxidation aperture is approximately an isosceles triangle with a rounded vertex angle, the distance from the center to the bottom of the isosceles triangle is shortest, and the distance from the center to two rounded bottom angles is longest. As can be seen from fig. 8, the direction in which the oxidation speed of the platform in the active region before correction is the fastest is the direction in which the center of the isosceles triangle is perpendicular to the base side thereof, the direction in which the oxidation speed is the slowest is the direction from the center of the isosceles triangle to the two base angles of the rounding treatment, and the base side of the isosceles triangle is approximately parallel to the main planar side direction of the substrate.

Figure 9 is a schematic cross-sectional view parallel to the substrate of a modified active region mesa using the 112 crystal plane. The shape of the cross section of the modified active region platform parallel to the substrate is as follows: the ellipse is cut by three curves (shown by gray areas in fig. 9) with openings facing away from the center, and after the ellipse is cut by the curves, the direction of two paths with the shortest length from the center to the edge of the ellipse is consistent with the direction of two paths with the longest distance from the center of the oxide aperture to the edge of the oxide aperture actually formed after the active region is oxidized before correction, and the point with the shortest distance from the center of the ellipse on the other curve is located on the major axis of the ellipse.

In this embodiment, it is preferable that a connection line between a point on the ellipse and the center of the ellipse is cut by the curve to have a maximum length of R1 to R2, where R2 is a shortest distance from the center of an oxide aperture actually formed after the mesa oxidation of the active region before the modification to an edge of the oxide aperture approximately parallel to the azimuthal crystal direction of the main flat side of the substrate, and R1 is a shortest distance from the center of an oxide aperture actually formed after the mesa oxidation of the active region before the modification to the other side of the oxide aperture.

In this embodiment, it is preferable that the ellipse satisfies the relation:wherein RA is 1/2 of the length of the major axis of the ellipse, RB is 1/2 of the length of the minor axis of the ellipse, and theta is the smaller included angle value of two included angles between the minor axis of the ellipse and two paths with the shortest length from the center to the edge of the ellipse after correction.

In this embodiment, it is preferred that the three curves do not intersect within the ellipse.

In the present embodiment, it is preferable that the curve is a circular arc having a radius R.

In another embodiment, the active region platform uses a 112 plane, and the curve is a conic section, a polygonal curve, or a combination thereof.

Example 4

In this embodiment, a vertical cavity surface emitting laser having a non-cylindrical mesa is further provided with an electrode contact layer between the first mirror layer and the substrate, after the oxidation of the sidewall of the non-cylindrical active region mesa is completed, the remaining portion of the first mirror layer is etched again to form a second mesa, the range of the second mesa is larger than the non-cylindrical active region mesa, the sidewall of the non-cylindrical active region mesa and the second mesa and the upper surface of the second mesa are passivated to provide a passivation layer, a filler is provided outside the passivation layer, and the filler may be at least one of Polyimide (PI), benzocyclobutene (BCB), SU-8, titanium (Ti), platinum (Pt) and gold (Au). The filler wraps the non-cylindrical active region platform and the second platform to form a circular stack structure. And arranging a first electrode on the upper surface of the non-cylindrical active region platform, and leading out a second electrode in the region of the electrode contact layer which is not covered by the filler.

The VCSEL structure portion other than the cylindrical active region mesa is not the key point of the present invention, and therefore, the arrangement of the VCSEL structure other than the non-cylindrical active region mesa will not be described in detail, and those skilled in the art can make other arrangements or modifications according to the actual needs.

Example 5

As shown in fig. 10, the preparation of the vertical cavity surface emitting laser with the non-cylindrical mesa includes the steps of:

s1: and (4) carrying out epitaxial growth on the wafer. Epitaxially growing an electrode contact layer on a substrate, growing a first mirror layer on the electrode contact layer, growing an active layer on the first mirror layer, and growing a second mirror layer on the active layer. The epitaxial growth of the wafer can adopt a molecular beam epitaxy method or a metal organic vapor deposition method or other methods disclosed in the prior art, and in the process of growing the second mirror layer, the oxidation limiting layer is grown at the position of the second mirror layer close to the activation layer, and the oxidation limiting layer is an AlGaAs layer with Al molar content of more than 95%.

S2: the reticle is designed to be used to form the cross-sectional pattern of the non-cylindrical active area mesa on the wafer surface.

Designing a photomask according to the crystal face type of the wafer, so that a cross section pattern of a non-cylindrical active region platform corresponding to the crystal face type can be formed on the surface of the wafer;

before designing a photomask, aiming at the crystal face type of the wafer, carrying out an experiment, firstly setting a cylindrical active region platform with the radius of R in the experiment, forming an experimental condition of a target oxidation aperture with the radius of R after side wall oxidation, and then obtaining the shape, the related direction and the length data of the actually formed oxidation aperture of the cylindrical platform with the radius of R after side wall oxidation by adopting the experimental condition.

In this embodiment, it is preferable that multiple experiments are performed on the same crystal plane type, the conditions of each experiment are set to be the same, and the average value or the fitting value of the multiple experiment results is taken as the final experiment result of the finally determined crystal plane type.

According to the experimental result, a photomask meeting the requirements is designed.

S3: and (6) photoetching. And photoetching by using the photomask to form a cross-sectional pattern of the non-cylindrical active area platform on the upper surface of the wafer.

S4: and etching to form a non-cylindrical active region platform, wherein the side wall of the non-cylindrical active region platform exposes the oxidation limiting layer. Using a conventional etching process, etching is performed according to the pattern formed on the surface of the wafer in step S3 to form a non-cylindrical active region mesa having an elliptical cross-section, which should ensure that the oxide confinement layer provided during the wafer growth is exposed on the sidewalls of the active region mesa.

S5: and oxidizing the side wall of the non-cylindrical active region platform to form an oxidation aperture. And carrying out side wall oxidation on the non-cylindrical active region platform with the oval cross section formed by etching to enable the oxidation limiting layer to form an aluminum oxide layer, thereby effectively limiting the flow range of carriers and the light emitting path.

S6: passivation and filler placement. And passivating the side wall of the non-cylindrical active region platform formed by etching, and filling the concave region formed for manufacturing the active region platform.

S7: and (4) preparing an electrode.

Example 6

In order to verify whether the shape of an oxidation aperture formed after the side wall oxidation of the non-cylindrical active region platform is close to a circle or a regular polygon, a comparison test is carried out on the active region platform adopting a 110 crystal face.

In the experiment, a circular mask as shown in fig. 11a was first designed, the diameter R of the circular mask being 36um, the expected shape of the oxide aperture formed being circular, the diameter R being 8 um. The shape and size of the actually formed oxidation pore diameter are as shown in fig. 11b, the shape of the oxidation pore diameter is approximately elliptical, the longest radial length b is 7.92um, the shortest radial length a is 6.04um, the ratio of the oxidation pore diameter length a to b is 6.04/7.92-0.76, and the minimum value of the included angle between the longest radial direction of the oxidation pore diameter and the X axis is approximately 40 degrees.

Then, 3 kinds of elliptical masks are designed, and the longest radial direction in fig. 11B is the B-axis direction of the elliptical mask, and the shortest radial direction in fig. 11B is the a-axis direction of the elliptical mask. The shapes of 3 kinds of elliptical masks are shown in FIGS. 11c, 11e and 11g, and the lengths of the A axis, the B axis, the ratio of the lengths of the A axis to the B axis and the degree of an included angle of 1 between the B axis and the X axis are shown in Table 1:

TABLE 1

Drawing number	Length of A axis	Length of B axis	Ratio of length of A-axis to length of B-axis	Degree of angle 1
					11c	34.2um	36um	0.95	40°
11e	37.8um	36um	1.05	40°
					11g	39.6um	36um	1.1	40°

In the test process, except for the shape and the size of the photomask, the rest test conditions are the same, the 3 kinds of elliptical photomasks are adopted to respectively form a graph on a wafer, etching is carried out according to the graph to form a non-cylindrical active region platform with the cross section shown in figures 11c, 11e and 11g, the side wall of the active region platform is oxidized to form an oxidation aperture, the shape and the size of the oxidation aperture corresponding to each photomask are observed, and the obtained test result is shown in figures 11d, 11f and 11 h.

After the active region mesa formed by the mask shown in fig. 11c is oxidized, the shape and size of the formed oxide aperture are shown in fig. 11d, the length a of the oxide aperture along the a-axis direction is 3.95um, the length B of the oxide aperture along the B-axis direction is 8.53um, and the ratio of the length a to the length B of the oxide aperture is 3.95/8.53 ═ 0.46. The shape of the oxide pore size can be found to resemble an ellipse.

After the active region mesa formed by the mask shown in fig. 11e is oxidized, the shape and size of the oxide aperture formed is shown in fig. 11f, the length a of the oxide aperture along the a-axis direction is 8.88um, the length B of the oxide aperture along the B-axis direction is 8.54um, and the ratio of the length a to the length B of the oxide aperture is 8.88/8.54, which is 1.03. The shape of the oxide pore size was found to closely match the shape of a circle, and this is evidenced by the ratio of the oxide pore size lengths a to b.

After the active region mesa formed by the mask shown in fig. 11g is oxidized, the shape and size of the formed oxide aperture are shown in fig. 11h, the length a of the oxide aperture along the a-axis direction is 9.88um, the length B of the oxide aperture along the B-axis direction is 8.20um, and the ratio of the length a to the length B of the oxide aperture is 9.88/8.20-1.20. The shape of the oxide pore size can be found to resemble an ellipse.

The test result shows that the shape of the oxide aperture can be effectively improved by changing the shape of the active area platform and adopting the shape of the active area platform, so that the shape of the oxide aperture is more regular, and the light emitted by the laser is more regular.

The above test results are only for the case that the active region platform adopts the 110 crystal plane, and are used to illustrate that the shape of the oxide aperture can be changed by changing the shape of the active region platform, and the tests for the active region platforms of other crystal planes are not repeated, and those skilled in the art can design and verify according to the technical scheme of the present application.

It should be understood that besides etching the non-cylindrical active region mesa whose sidewalls need to be oxidized, a person skilled in the art may make various modifications to the other structures of the laser as desired, and may also make various designs on the cross-section of the non-cylindrical active region mesa as desired, without departing from the scope of the present invention in its essence.

It should be noted that the above embodiments are only used for illustrating the technical solution of the present invention, and not for limiting the same; although the foregoing embodiments illustrate the invention in detail, those skilled in the art will appreciate that: it is possible to modify the technical solutions described in the foregoing embodiments or to substitute some or all of the technical features thereof, without departing from the scope of the technical solutions of the present invention.