VCSEL unit with asymmetric oxidation structure
阅读说明：本技术 一种具有非对称氧化结构vcsel单元 (VCSEL unit with asymmetric oxidation structure ) 是由 梁栋 于 2019-12-23 设计创作，主要内容包括：本发明提供一种具有非对称氧化结构VCSEL单元,通过在器件内设有上下两组不同氧化层即第一氧化层组、第二氧化层组,第二氧化层组的两个区域内侧边缘与发光孔的边缘在竖直方向上具有部分重叠,产生在水平面不同方向上非对称的光束缚作用的技术手段,实现非对称的光发散角的效果,打破现有技术中光场发散角只能对称的局限性。(The invention provides a VCSEL unit with an asymmetric oxidation structure, which adopts the technical means that an upper group of oxide layers and a lower group of oxide layers, namely a first oxide layer group and a second oxide layer group, are arranged in a device, the inner side edges of two areas of the second oxide layer group are partially overlapped with the edge of a light emitting hole in the vertical direction, and the asymmetric light beam binding effect in different directions of a horizontal plane is generated, so that the effect of an asymmetric light divergence angle is realized, and the limitation that the divergence angle of a light field in the prior art can only be symmetric is broken through.)
1. A VCSEL unit with an asymmetric oxidation structure is characterized by comprising a semiconductor epitaxial structure layer and a mesa structure, wherein an upper oxidation layer group and a lower oxidation layer group are arranged in the mesa structure;
the first oxide layer group in the two oxide layer groups is formed by oxidizing the peripheral channels of the mesa structure to the center of the mesa structure, and light emitting holes of the device are limited;
the second oxidation layer group comprises two areas which extend from two outer sides opposite to the mesa structures to the center of the mesa structures on the horizontal plane and are spaced from each other; the part between the two areas has no shelter to the light emitting hole in the vertical direction; the inner side edges of the two regions have a partial overlap with the edge of the light emitting hole in the vertical direction.
2. The VCSEL unit with the asymmetric oxidation structure of claim 1, wherein the oxide layer group comprises an oxide layer.
3. The VCSEL unit with the asymmetric oxidation structure of claim 1, wherein the oxidation layer group comprises at least two oxidation layers.
4. The VCSEL unit with the asymmetric oxidation structure of claim 1, wherein the first oxide layer group is arranged above the second oxide layer group.
5. The VCSEL unit with the asymmetric oxidation structure of claim 1, wherein the first oxide layer set is arranged below the second oxide layer set.
6. The VCSEL unit with the asymmetric oxide structure of claim 1, wherein the mesa sidewall is planar and the corresponding trench depth reaches a position of an upper surface of a substrate layer.
7. The VCSEL unit with the asymmetric oxidation structure as claimed in claim 1, wherein the mesa sidewall is stepped and has steps on the upper surface of the etch stop layer on the quantum well and below the quantum well, respectively.
8. The VCSEL unit with the asymmetric oxidation structure as claimed in claim 1, wherein the shape of the light emitting hole defined by the first oxidation layer group is circular, elliptical, standard polygonal, polygonal with arc edge; the second oxide layer group defines a non-oxide portion extending from one side to the other side of the mesa structure in the horizontal direction.
9. The VCSEL unit having an asymmetric oxide structure of claim 1, wherein: the semiconductor epitaxial structure layer comprises a P-type distributed Bragg reflector, a quantum well layer, an N-type distributed Bragg reflector and an N-type substrate layer.
10. A VCSEL unit having an asymmetric oxide structure, according to claim 9, wherein: the P-type distributed Bragg reflector and the N-type distributed Bragg reflector are made of Al with different Al and Ga componentsxGa（1-x）As, or In of different composition(1-x)GaxAsyP(1-y)Or one or more selected from AlN, GaN, InGaN, AlGaN or SiN, SiO and SiON; the quantum well layer material is selected from GaThe VCSEL unit comprises one or more of As, AlGaAs, InGaAs, InGaP, GaN, InGaN, AlGaN or AlInGaNAsP, and the VCSEL unit comprises a P/N electrode metal layer and a pad metal, wherein the P/N electrode metal layer and the pad metal are made of one or more of Ti, Pt, Au, Pt, Pd, Ge and alloys thereof.
11. A VCSEL unit having an asymmetric oxide structure according to any of claims 1-10, wherein: and replacing the second oxide layer group by a dielectric layer formed by an air layer and/or SiN and/or SiO and/or SiON material.
12. The VCSEL unit of claim 11, wherein the dielectric layer is formed by etching away a portion or all of the second oxide layer.
Technical Field
The invention relates to the technical field of Vertical Cavity Surface Emitting Lasers (VCSELs), in particular to a VCSEL unit with an asymmetric oxidation structure.
Background
Vertical Cavity Surface Emitting Lasers (VCSELs) are mainly developed on the basis of III-V group compound semiconductor materials. Unlike LED and EEL, VCSEL can realize Laser with small threshold current easily, has higher wavelength temperature stability than common EEL and can realize single longitudinal mode, even single transverse mode and ultra-narrow bandwidth light-emitting spectrum. Compared with an EEL (external electrode active surface) module, the VCSEL can realize a large-area two-dimensional array on a chip layer by being adhered to a rear-end module, and meanwhile, due to the fact that light is emitted from the surface, the thickness of the whole module can be very thin, even the VCSEL can be directly surface-mounted on a driving circuit board, and extra parts such as a reflecting prism are not needed. The traditional VCSEL is widely applied to the fields of optical communication, optical interconnection, optical storage and the like, and in recent years, with the large-scale application of technologies such as smart phones, face recognition, 3D detection modeling and the like, the VCSEL becomes the most important semiconductor light source in the field of consumer electronics.
At present, in numerous intelligent devices such as smart phones, there is a great market demand for infrared Illumination (IR) projection modules, which play a crucial role in specific applications such as TOF measurement and security camera devices, and VCSELs are the most central devices in infrared illumination projection modules. Existing VCSELs have only symmetrical divergence angles in the x and y directions, but there are many applications where VCSELs with different divergence angles in the x and y directions are required, such as to generate a rectangular or elliptical illumination field. In general, the optical field of the VCSEL aperture is x and y axis symmetric or axisymmetric. If the symmetry of the divergence angle of the light field is to be broken, the symmetry of the light field confinement needs to be broken. The prior art is lack of VCSEL devices which can meet the requirement that an optical field has a certain deflection angle.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a VCSEL unit with an asymmetric oxidation structure, which comprises a semiconductor epitaxial structure layer and a mesa structure, wherein an upper oxidation layer group and a lower oxidation layer group are arranged in the mesa structure;
the first oxide layer group in the two oxide layer groups is formed by oxidizing the peripheral channels of the mesa structure to the center of the mesa structure, and light emitting holes of the device are limited;
the trench may be a single continuous surrounding mesa or may be discrete individual holes surrounding the mesa.
The second oxidation layer group comprises two areas which extend from two outer sides opposite to the mesa structures to the center of the mesa structures on the horizontal plane and are spaced from each other; the part between the two areas has no shelter to the light emitting hole in the vertical direction;
the inner side edges of the two regions have a partial overlap with the edge of the light emitting hole in the vertical direction.
The oxide layer group can be arranged above and below the quantum hydrazine.
The shape of the second oxide layer group at the part overlapped with the first oxide layer group is generally directly followed by the shape of the first oxide layer group at the part (no redundant oxide layer is arranged above the light emitting hole of the first layer for blocking, so that the light emitting efficiency of the device is higher), and what the shape of the other parts which are not overlapped on the outline is not important as long as the part is outside the first oxide layer hole and the constraint on the light field is weak.
For example, for a rectangular or square light emitting hole, the outline of the second oxide layer group and the outline of the first oxide layer group are overlapped in position in one direction and are not overlapped in position in the other direction; for a circular or elliptical light emitting opening, the contour of the second oxide layer group and the contour of the first oxide layer group overlap with each other by two opposing arcs.
The inner side edges of the two regions are overlapped with the edge of the light emitting hole in the vertical direction, and the light emitting of the device is not affected if the error is within 1-2 um.
Preferably, the oxide layer group includes one oxide layer.
Preferably, the oxide layer group comprises at least two oxide layers.
Theoretically, there are more oxidation layer groups in the direction of large optical field limitation, so that the difference of effective refractive index of the longitudinal optical field in the aperture and the effective refractive index of the longitudinal optical field in the direction of large optical field limitation is larger than that in the direction of small oxidation layer groups, and the limitation of the direction on the optical field is increased due to the fact that the oxidation layer groups are added in the direction, therefore, the divergence angle in the direction can be increased by the technical means adopted in the scheme of the invention.
Preferably, the first oxide layer group is located above the second oxide layer group.
Preferably, the first oxide layer group is arranged below the second oxide layer group.
The upper and lower orders of the first oxide layer group and the second oxide layer group can be exchanged as long as the process allows, and at least one of the two groups needs to play a main current limiting role.
Preferably, the side wall of the mesa structure is a plane, and the corresponding depth of the trench reaches the position of the upper surface of the substrate layer.
Preferably, the side wall of the mesa structure is of a step type, and steps are respectively arranged on the upper surface of the etching stopping layer on the quantum well and below the quantum well.
Preferably, the shape of the light emitting hole defined by the first oxide layer group is circular, oval, standard polygon or polygon with arc edges; the second oxidation layer group limits a non-oxidation part extending from one side of the mesa structure to the other side in the horizontal direction;
preferably, the semiconductor epitaxial structure layer comprises a P-type distributed bragg reflector, a quantum well layer, an N-type distributed bragg reflector and an N-type substrate layer.
Preferably, the materials of the P-type distributed Bragg reflector and the N-type distributed Bragg reflector are Al with different Al and Ga compositionsxGa（1-x）As, or In of different composition(1-x)GaxAsyP(1-y)Or one or more selected from AlN, GaN, InGaN, AlGaN or SiN, SiO and SiON; the quantum well layer material is selected from one or more of GaAs, AlGaAs, InGaAs, InGaP, GaN, InGaN, AlGaN or AlInGaNAsP, the VCSEL unit comprises a P/N electrode metal layer and a pad metal, and the P/N electrode metal layer and the pad metal material are selected from one or more of Ti, Pt, Au, Pt, Pd, Ge and alloys thereof.
A VCSEL unit with asymmetric oxide structure as described in any of the above paragraphs, wherein the second oxide layer group is replaced by a dielectric layer formed by an air layer and/or SiN and/or SiO and/or SiON material.
The red LED can use this rule for reference, and the oxide layer is etched away and replaced by an air layer. In principle, this technique can be used as long as the surface emitting light source has a low refractive index medium (e.g., an oxide layer) to confine the light.
Preferably, the dielectric layer is formed by etching away a part or all of the second oxide layer group.
According to the VCSEL unit with the asymmetric oxidation structure, the technical means that the upper layer oxide layer group and the lower layer oxide layer group are arranged above the quantum well layer is adopted, the beneficial effect that different divergence angles are generated in different directions is achieved, and the limitation that the divergence angles of a light field in the prior art can only be symmetrical is broken through.
Drawings
Fig. 1 is a diagram of a square VCSEL device cell.
FIG. 2 is a schematic diagram of a VCSEL device unit with other shapes.
Fig. 3 is a process diagram of a
Fig. 4 is a process diagram of a
Fig. 5 is a process diagram of a
Fig. 6 is a process diagram of a
FIG. 7 is a diagram A illustrating the technical effect of changing the original circular far field of the VCSEL into an elliptical far field; and B, changing the original square far field of the VCSEL into a rectangular far field.
In the figure: 1. a first oxide layer group; 2. a second oxide layer group; 3. etching the stop layer; 4. a quantum well light emitting region; 5. a
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.
As shown in fig. 1, the symmetry of the x and y optical fields is broken by making different oxide layer groups in the x and y directions (x and y refer to different directions, not necessarily perpendicular to each other) so that the effective refractive indices in the x and y directions differ, i.e. the confinement effect on the optical field differs. The one-directional divergence angle that makes the light field confinement small is small. The direction of large optical confinement has a large divergence angle, and the direction of small optical confinement has only a few oxide layer groups (the first oxide layer group shown in fig. 1). The layers are also arranged in the other direction, so that an approximately square aperture is formed, and the current limiting function is achieved; FIG. 2 is a schematic diagram of a VCSEL device unit with other shapes.
As shown in fig. 3, a: sectional view along the y-direction, sectional view along the x-direction, C: and (4) a top view. A set of preferred embodiments is shown, the specific embodiments are as follows: 1. etching the channels on two sides in one direction of x or y, oxidizing the two layers together, and then protecting the two layers by using a dielectric; 2. the trench is then etched in the other direction (either a combination of dry and wet etching or a pure wet etch) stopping the etch stop layer between the two oxide layers, thus oxidizing only the upper oxide layer set. Thus forming different oxidation structures in the x and y directions; fig. 4 is a process diagram of a
As shown in the specific structural diagram of FIG. 5, A is a sectional view along the x or y direction, B is a top view of the first step, C is a sectional view along the x direction, D is a sectional view along the y direction, and E: and the second step is top view. A set of preferred embodiments is shown, the specific embodiments are as follows: 1. the
FIG. 7 is a diagram of the technical effect wherein A, the original circular far field of the VCSEL is changed into an elliptical far field; and B, changing the original square far field of the VCSEL into a rectangular far field.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
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