阅读说明：本技术 一种改善半导体激光器掺杂均匀性的方法 (Method for improving doping uniformity of semiconductor laser ) 是由 程洋 郭银涛 王俊 刘恒 于 2020-12-23 设计创作，主要内容包括：本发明公开了一种改善半导体激光器掺杂均匀性的方法,包括：将衬底置于外延生长设备的基座上,衬底朝向基座表面的边缘和基座朝向衬底的表面不接触；在衬底背离基座的表面依次生长n型外延层、有源层和p型外延层,生长p型外延层时所需的生长条件敏感掺杂源从外延生长设备的两个气路或三个气路通入,两个气路或三个气路垂直设置。通过实施本发明,改变衬底和基座的接触性,使得衬底边缘和基座边缘的接触性变差,可以有效调节衬底表面的温度均匀性,从而可以减小温度对掺杂源掺杂不均匀的影响；并且,采用两路或三路同时通入生长条件敏感掺杂源,可以在降低温度对生长条件敏感掺杂源掺杂均匀性影响的基础上,改善生长条件敏感掺杂源的掺杂均匀性。(The invention discloses a method for improving the doping uniformity of a semiconductor laser, which comprises the following steps: placing the substrate on a base of the epitaxial growth equipment, wherein the edge of the surface of the substrate facing the base is not contacted with the surface of the base facing the substrate; and an n-type epitaxial layer, an active layer and a p-type epitaxial layer are sequentially grown on the surface of the substrate, which is far away from the base, a growth condition sensitive doping source required when the p-type epitaxial layer is grown is introduced from two gas paths or three gas paths of the epitaxial growth equipment, and the two gas paths or the three gas paths are vertically arranged. By implementing the invention, the contact between the substrate and the base is changed, so that the contact between the edge of the substrate and the edge of the base is poor, the temperature uniformity of the surface of the substrate can be effectively adjusted, and the influence of temperature on the uneven doping of the doping source can be reduced; and moreover, the growth condition sensitive doping source is introduced by two or three paths simultaneously, so that the doping uniformity of the growth condition sensitive doping source can be improved on the basis of reducing the influence of the temperature on the doping uniformity of the growth condition sensitive doping source.)

1. A method for improving doping uniformity of a semiconductor laser, comprising:

placing a substrate on a base of an epitaxial growth device, wherein the edge of the substrate facing the surface of the base is not in contact with the surface of the base facing the substrate;

and sequentially growing an n-type epitaxial layer, an active layer and a p-type epitaxial layer on the surface of the substrate, which is far away from the base, wherein a growth condition sensitive doping source required when the p-type epitaxial layer is grown is introduced from two gas circuits or three gas circuits of the epitaxial growth equipment, and the two gas circuits or the three gas circuits are vertically arranged.

2. A method for improving doping uniformity of a semiconductor laser as defined in claim 1, wherein placing the substrate on a pedestal of an epitaxial growth apparatus comprises:

depositing a thermal expansion layer on one side surface of a substrate, wherein the thermal expansion coefficient of the thermal expansion layer is larger than that of the substrate;

and placing the substrate on a base of epitaxial growth equipment, wherein the surface of the substrate, on which the thermal expansion layer is deposited, is arranged towards the base, and the edge of the thermal expansion layer is not in contact with the surface of the base, which faces the substrate.

3. A method as claimed in claim 1 wherein the surface of the pedestal facing the substrate is convex.

4. The method of claim 2 wherein the substrate is a gallium arsenide substrate and the thermal expansion layer is a silicon nitride thermal expansion layer, the thermal expansion layer having a thickness of 100nm to 2000 nm.

5. A method as claimed in claim 1 wherein the growth condition sensitive dopant source comprises: the carbon source comprises a carbon source, a zinc source and a magnesium source, wherein the carbon source is a carbon tetrabromide carbon source.

6. A method for improving doping uniformity of a semiconductor laser as defined in claim 1 wherein the semiconductor lasers comprise edge emitting semiconductor lasers and vertical cavity surface emitting semiconductor lasers.

7. The method of claim 1 wherein the epitaxial growth apparatus comprises an upper layer gas path, a middle layer gas path, or a lower layer gas path,

when the growth condition sensitive doping sources required for growing the p-type epitaxial layer are introduced from the two gas paths, the growth condition sensitive doping sources are introduced from the upper layer gas path and the middle layer gas path, or the growth condition sensitive doping sources are introduced from the middle layer gas path and the lower layer gas path.

8. The method according to claim 7, wherein the ratio of the gas flow rates of the growth condition sensitive doping sources introduced into the upper layer gas circuit and the middle layer gas circuit is 0.5 to 3; and the ratio of the gas flow of the growth condition sensitive doping source introduced into the lower layer gas path and the middle layer gas path is 0.5-3.

9. A method for improving the doping uniformity of a semiconductor laser as defined in claim 1, wherein said p-type epitaxial layer comprises a p-type upper waveguide layer, a p-type upper confinement layer and a p-type contact layer, or said p-type epitaxial layer comprises a p-type distributed bragg mirror layer.

10. A method for improving doping uniformity of a semiconductor laser as defined in claim 1, wherein said n-type epitaxial layer comprises an n-type lower confinement layer and an n-type lower waveguide layer, or said n-type epitaxial layer comprises an n-type distributed bragg mirror layer.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a method for improving doping uniformity of a semiconductor laser.

Background

The semiconductor laser is an important photoelectric device and has wide application in the fields of sensing, lighting, communication, pumping and the like. In order to reduce the fabrication cost of semiconductor lasers, three, four or even six inch gallium arsenide substrates are increasingly being used in epitaxial processes. At present, a planetary reaction chamber is often used for growing the epitaxial wafer of the semiconductor laser, and the scheme of combining substrate rotation and graphite big disc revolution is adopted to realize the uniform growth of the epitaxial layer on the whole substrate surface. By adopting the scheme, the standard deviation of the thickness of the epitaxial layer on the whole epitaxial layer can be less than 0.5%.

However, when the epitaxial layer is grown by this method, the doping concentration uniformity of the dopant source on the whole epitaxial layer cannot meet the required requirement, especially the doping concentration uniformity of the p-type epitaxial layer. The non-uniformity of the doping concentration affects the electrical characteristics of the semiconductor laser device, and further affects various performance parameters of the semiconductor laser device, including slope efficiency, threshold current and the like, thereby causing adverse effects on large-scale batch and uniform production of the semiconductor laser device.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method for improving doping uniformity of a semiconductor laser, so as to solve the technical problem in the prior art that the doping concentration uniformity of a dopant source on an epitaxial layer cannot meet a required requirement.

The technical scheme provided by the invention is as follows:

the embodiment of the invention provides a method for improving doping uniformity of a semiconductor laser, which comprises the following steps: placing a substrate on a base of an epitaxial growth device, wherein the edge of the substrate facing the surface of the base is not in contact with the surface of the base facing the substrate; and sequentially growing an n-type epitaxial layer, an active layer and a p-type epitaxial layer on the surface of the substrate, which is far away from the base, wherein a growth condition sensitive doping source required when the p-type epitaxial layer is grown is introduced from two gas circuits or three gas circuits of the epitaxial growth equipment, and the two gas circuits or the three gas circuits are vertically arranged.

Optionally, placing the substrate on a susceptor of an epitaxial growth apparatus, comprising: depositing a thermal expansion layer on one side surface of a substrate, wherein the thermal expansion coefficient of the thermal expansion layer is larger than that of the substrate; and placing the substrate on a base of epitaxial growth equipment, wherein the surface of the substrate, on which the thermal expansion layer is deposited, is arranged towards the base, and the edge of the thermal expansion layer is not in contact with the surface of the base, which faces the substrate.

Optionally, a surface of the base facing the substrate is convex.

Optionally, the substrate is a gallium arsenide substrate, the thermal expansion layer is a silicon nitride thermal expansion layer, and the thickness of the thermal expansion layer is 100nm to 2000 nm.

Optionally, the growth condition sensitive dopant source comprises: the carbon source comprises a carbon source, a zinc source and a magnesium source, wherein the carbon source is a carbon tetrabromide carbon source.

Alternatively, the semiconductor laser includes an edge-emitting semiconductor laser and a vertical cavity surface-emitting semiconductor laser.

Optionally, the epitaxial growth equipment comprises an upper layer gas circuit, a middle layer gas circuit or a lower layer gas circuit, and when the growth condition sensitive doping source required for growing the p-type epitaxial layer is introduced from the two gas circuits, the growth condition sensitive doping source is introduced from the upper layer gas circuit and the middle layer gas circuit, or the growth condition sensitive doping source is introduced from the middle layer gas circuit and the lower layer gas circuit.

Optionally, the ratio of the gas flow of the growth condition sensitive doping source introduced into the upper layer gas path and the middle layer gas path is 0.5 to 3; and the ratio of the gas flow of the growth condition sensitive doping source introduced into the lower layer gas path and the middle layer gas path is 0.5-3.

Optionally, the p-type epitaxial layer comprises a p-type upper waveguide layer, a p-type upper confinement layer and a p-type contact layer, or the p-type epitaxial layer comprises a p-type distributed bragg mirror layer.

Optionally, the n-type epitaxial layer includes an n-type lower confinement layer and an n-type lower waveguide layer, or the n-type epitaxial layer includes an n-type distributed bragg mirror layer.

The technical scheme provided by the invention has the following effects:

according to the method for improving the doping uniformity of the semiconductor laser, the contact between the edge of the substrate and the edge of the base is poor by changing the contact between the substrate and the base, the temperature uniformity of the surface of the substrate can be effectively adjusted, and the influence of temperature on the non-uniformity of doping source doping can be reduced; and two or three paths of carbon sources are simultaneously introduced into the growth condition sensitive doping source, and the air flow heights of the carbon sources are different, so that the time for the two or three paths of carbon sources to reach the surface of the substrate is different, the position and the concentration of the carbon sources to reach the surface of the substrate can be effectively adjusted, and the doping uniformity of the growth condition sensitive doping source can be improved on the basis of reducing the influence of the temperature on the doping uniformity of the growth condition sensitive doping source. Therefore, the method for improving the doping uniformity of the semiconductor laser device provided by the embodiment of the invention effectively improves the doping uniformity of the p-type epitaxial layer of the semiconductor laser device, improves the consistency of the performance of the semiconductor laser device and promotes the large-scale production of the semiconductor laser device.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a flow chart of a method of improving doping uniformity of a semiconductor laser according to an embodiment of the present invention;

FIG. 2 is a block diagram of a structure of a substrate and susceptor contact according to an embodiment of the present invention;

FIG. 3 is a block diagram of a substrate and susceptor contact according to another embodiment of the present invention;

fig. 4 is a block diagram of a structure of a three-layer gas circuit of an epitaxial growth apparatus according to an embodiment of the present invention;

fig. 5 is a schematic structural view of an edge-emitting semiconductor laser according to an embodiment of the present invention;

fig. 6 is a schematic structural view of a vertical cavity surface emitting semiconductor laser according to an embodiment of the present invention.

Detailed Description

As described in the background art, the current epitaxial growth method of a semiconductor laser cannot ensure the doping concentration uniformity of the doping source on the whole epitaxial layer, especially the doping concentration uniformity of the p-type epitaxial layer, during the growth process. The non-uniformity of the doping concentration of the P-type epitaxial layer mainly comes from the following sources: firstly, the back surface and the edge of the substrate are both contacted with the base, so that the edge part of the substrate receives transmitted heat from the surface and the side surface of the base, the temperature of the surface of the substrate presents non-uniform distribution, the non-uniformity of the distribution is gradually increased along with the increase of the size of a substrate wafer, and the carbon doping efficiency of a commonly used carbon tetrabromide (CBr 4 for short) source for p-type doping is highly sensitive to the temperature; secondly, metal organic matter sources (MO sources for short, including TMGa, TMAl, TMin and the like) are gradually consumed in the growth process of the surface of the substrate, so that the difference between the V group ratio and the III group ratio is large, and the two parameters also have great influence on the doping efficiency of carbon tetrabromide.

Based on this, an embodiment of the present invention provides a method for improving doping uniformity of a semiconductor laser, including: placing the substrate on a base of the epitaxial growth equipment, wherein the edge of the surface of the substrate facing the base is not contacted with the surface of the base facing the substrate; and an n-type epitaxial layer, an active layer and a p-type epitaxial layer are sequentially grown on the surface of the substrate, which is far away from the base, a growth condition sensitive doping source required when the p-type epitaxial layer is grown is introduced from two gas paths or three gas paths of the epitaxial growth equipment, and the two gas paths or the three gas paths are vertically arranged.

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. 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 protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

An embodiment of the present invention provides a method for improving doping uniformity of a semiconductor laser, as shown in fig. 1, the method includes the following steps:

step S101: placing the substrate on a base of the epitaxial growth equipment, wherein the edge of the surface of the substrate facing the base is not contacted with the surface of the base facing the substrate; in one embodiment, the epitaxial growth apparatus may be a Metal-organic Chemical Vapor Deposition (MOCVD) apparatus.

In order to keep the edge of the substrate and the susceptor out of contact, in one embodiment, a thermal expansion layer may be deposited on one side surface of the substrate before the substrate is placed on the susceptor, the thermal expansion layer having a coefficient of thermal expansion greater than that of the substrate; when the substrate is placed on a base of the epitaxial growth equipment, the surface of the substrate deposited with the thermal expansion layer can be arranged towards the base, and when the temperature of the base rises, the edge of the thermal expansion layer and the surface of the base, which faces the substrate, can be kept out of contact.

In one embodiment, the substrate may be a gallium arsenide substrate, the thermal expansion layer is a silicon nitride thermal expansion layer, and the thickness of the thermal expansion layer is 100nm to 2000 nm. Specifically, the thermal expansion layer may be formed by Plasma Enhanced Chemical Vapor Deposition (PECVD) or Low Pressure Chemical Vapor Deposition (LPCVD); the coefficient of thermal expansion of the thermal expansion layer may be adjusted by adjusting deposition parameters of the thermal expansion layer such that the coefficient of thermal expansion of the thermal expansion layer is greater than the coefficient of thermal expansion of the substrate. Therefore, when the susceptor is heated and an epitaxial layer grows on the substrate, the thermal expansion layer generates compressive strain, and as shown in fig. 2, the substrate becomes concave, so that the contact between the edge position of the substrate and the susceptor is deteriorated, the edge temperature is reduced, and the difference between the edge temperature and the center temperature of the substrate can be improved.

In an embodiment, the edge of the substrate and the susceptor may also be adapted in such a way that they do not touch. In one embodiment, the surface of the susceptor on which the substrate is placed may be treated, as shown in fig. 3, so that the surface assumes a convex shape, so that the center of the substrate and the susceptor may be brought into contact after the substrate is placed, while the edge of the substrate and the edge of the susceptor are not brought into contact, so that when the susceptor is heated, the edge temperature may be reduced, and thus the difference between the edge and center temperatures of the substrate may be improved.

Step S102: and an n-type epitaxial layer, an active layer and a p-type epitaxial layer are sequentially grown on the surface of the substrate, which is far away from the base, a growth condition sensitive doping source required when the p-type epitaxial layer is grown is introduced from two gas paths or three gas paths of the epitaxial growth equipment, and the two gas paths or the three gas paths are vertically arranged. In one embodiment, growing the condition-sensitive dopant source comprises: the carbon source comprises a carbon source, a zinc source and a magnesium source, wherein the carbon source is a carbon tetrabromide carbon source.

In an embodiment, the epitaxial growth apparatus includes an upper layer gas circuit, a middle layer gas circuit or a lower layer gas circuit, and when the growth condition sensitive doping sources required for growing the p-type epitaxial layer are introduced from the two gas circuits, the growth condition sensitive doping sources are introduced from the upper layer gas circuit and the middle layer gas circuit, or the growth condition sensitive doping sources are introduced from the middle layer gas circuit and the lower layer gas circuit, as shown in fig. 4, the growth condition sensitive doping sources are introduced from the upper layer gas circuit and the middle layer gas circuit. Wherein, the proportion of the gas flow of the growth condition sensitive doping source introduced into the upper layer gas path and the middle layer gas path is 0.5 to 3; the ratio of the gas flow of the growth condition sensitive doping source introduced into the lower layer gas path and the middle layer gas path is 0.5-3.

At present, in the conventional growth process of a p-type epitaxial layer, a metal organic source (MO source for short, including TMGa, TMAl, TMIn, etc.), a V-group dopant source and a carbon source need to be introduced, wherein the MO source is gradually consumed along the radial direction (diameter direction) of a substrate, and the total amount of the V-group source is substantially kept unchanged, so that the V/III ratio (the ratio of the V-group dopant source to the MO source) and the ratio of the MO source to the carbon source dopant source are gradually changed along the radial direction of the substrate, which results in that the concentration of the carbon source along the radial direction of the substrate and the doping efficiency are continuously changed, and thus the concentration of carbon finally incorporated into the epitaxial layer is also continuously changed along the radial direction of the substrate. In this example, two or three carbon sources are used. Because the gas flow heights of the carbon sources are different, the time for the two or three carbon sources to reach the surface of the substrate is different. Therefore, the position and the concentration of the carbon source reaching the surface of the substrate can be effectively adjusted by adjusting the gas flow of the carbon source introduced along the single upper-layer gas circuit or the single lower-layer gas circuit.

According to the method for improving the doping uniformity of the semiconductor laser, the contact between the edge of the substrate and the edge of the base is poor by changing the contact between the substrate and the base, the temperature uniformity of the surface of the substrate can be effectively adjusted, and the influence of temperature on the non-uniformity of doping source doping can be reduced; and two or three paths of carbon sources are simultaneously introduced into the growth condition sensitive doping source, and the air flow heights of the carbon sources are different, so that the time for the two or three paths of carbon sources to reach the surface of the substrate is different, the position and the concentration of the carbon sources to reach the surface of the substrate can be effectively adjusted, and the doping uniformity of the growth condition sensitive doping source can be improved on the basis of reducing the influence of the temperature on the doping uniformity of the growth condition sensitive doping source. Therefore, the method for improving the doping uniformity of the semiconductor laser device provided by the embodiment of the invention effectively improves the doping uniformity of the p-type epitaxial layer of the semiconductor laser device, improves the consistency of the performance of the semiconductor laser device and promotes the large-scale production of the semiconductor laser device.

In one embodiment, the above method for improving the doping uniformity of a semiconductor laser can be used for edge emitting semiconductor lasers and vertical cavity surface emitting semiconductor lasers. When the p-type epitaxial layer is used for an edge-emitting semiconductor laser, the p-type epitaxial layer comprises a p-type upper waveguide layer, a p-type upper limiting layer and a p-type contact layer, and the n-type epitaxial layer comprises an n-type lower limiting layer and an n-type lower waveguide layer. When used in a vertical cavity surface emitting semiconductor laser, the p-type epitaxial layer includes a p-type distributed bragg mirror layer and the n-type epitaxial layer includes an n-type distributed bragg mirror layer.

Example 2

The method for improving the doping uniformity of the semiconductor laser provided by the embodiment of the invention is described by taking an edge-emitting semiconductor laser as an example, wherein the edge-emitting semiconductor laser is a 980nm edge-emitting semiconductor laser.

First, the temperature uniformity of the substrate surface during epitaxial growth is adjusted. Specifically, silicon nitride can be deposited on the back of the gallium arsenide substrate by adopting a PECVD (plasma enhanced chemical vapor deposition) or LPCVD (low pressure chemical vapor deposition) process, the thickness of the deposited silicon nitride is 100 nm-2000 nm, the thermal expansion coefficient of the silicon nitride can be larger than that of the gallium arsenide substrate by adjusting the substrate parameters of the silicon nitride, when the gallium arsenide substrate is placed on a base of MOCVD (metal organic chemical vapor deposition) equipment to be heated, a silicon nitride film generates compressive strain, the gallium arsenide substrate becomes concave, and therefore the contact between the edge position of the gallium arsenide substrate and the base is poor, and the edge temperature is reduced; the temperature uniformity of the surface of the substrate can be effectively adjusted. In addition, the contact condition of the edge of the gallium arsenide substrate and the base can be changed by modifying the surface of the base into a convex shape under the condition that silicon nitride is not deposited, so that the effect of adjusting the temperature uniformity of the surface of the substrate is achieved.

Secondly, on the basis of adjusting the temperature uniformity of the surface of the substrate, the concentration distribution of the carbon tetrabromide doping source on the surface of the substrate during epitaxial growth can be adjusted. Specifically, the epitaxial growth process for the semiconductor laser can be realized according to the following steps: as shown in FIG. 5, after the GaAs substrate was placed on the susceptor of the MOCVD apparatus and heated, a GaAs buffer layer was grown to a thickness of 400nm and doped with Si to a concentration of 3e¹⁸/cm³(ii) a Introducing TMGa and AsH in the growth process₃And Si₂H₆(ii) a Growing an n-type AlGaAs lower limiting layer with a thickness of 2000nm, an Al component of 60%, and doped silicon with a concentration of 1e¹⁸/cm³(ii) a TMGa, TMAl and AsH are introduced in the growth process₃And Si₂H₆(ii) a Growing n-type AlGaAs lower waveguide layer with thickness of 800nm, Al content of 15%, doped silicon with concentration of 3e¹⁷/cm³(ii) a TMGa, TMAl and AsH are introduced in the growth process₃And Si₂H₆(ii) a Growing a GaAs quantum barrier layer with the thickness of 20nm and without doping, and introducing TMGa and AsH3 in the growing process; growing InGaAs quantum well layer with thickness of 7nm and without doping, introducing TMGa, TMIn and AsH during growth process₃(ii) a Growing a GaAs quantum barrier layer with the thickness of 20nm and without doping, and introducing TMGa and AsH in the growth process₃(ii) a Growing p-type AlGaAs upper waveguide layer with thickness of 400nm, Al content of 15%, doping carbon with concentration of 4e¹⁷/cm³Is living in natureIntroducing TMGa, TMAl and AsH in the long process₃And CBr₄(ii) a Growing a p-type AlGaAs upper limiting layer with a thickness of 1000nm, an Al component of 60%, and a carbon-doped concentration of 1e¹⁸/cm³Introducing TMGa, TMAl and AsH in the growth process₃And CBr 4; growing a p-type GaAs contact layer with a thickness of 500nm, doping with carbon and a concentration of 4e¹⁹/cm³Introducing TMGa and AsH in the growth process₃And CBr₄。

For the doping source introduced in the epitaxial growth process, wherein, AsH₃Introducing TMGa and TMAl from the upper layer gas circuit and the lower layer gas circuit, and CBr₄The gas circuit is introduced from the upper layer gas circuit and the middle layer gas circuit or from the middle layer gas circuit and the lower layer gas circuit or from the upper layer gas circuit, the middle layer gas circuit and the lower layer gas circuit. Specifically, when the doping sources are introduced, the corresponding doping source is introduced from the corresponding gas path when each epitaxial layer is grown according to the doping sources required by the different epitaxial layers.

During the growth of the epitaxial layer, the MO sources (TMGa and TMAl) are gradually consumed along the radial direction (diameter direction) of the substrate, while the group V source (AsH)₃) The total amount of the carbon source is kept basically constant, so that the V/III ratio (the ratio of the V-group doping source to the MO source flow) and the ratio of the MO source to the carbon source doping source are gradually changed along the radial direction of the substrate, the concentration of the carbon source along the radial direction of the substrate and the doping efficiency are continuously changed, and the concentration of the carbon finally incorporated into the epitaxial layer is also continuously changed along the radial direction of the substrate. In this example, two or three carbon sources are used. Because the gas flow heights of the carbon sources are different, the time for the two or three carbon sources to reach the surface of the substrate is different. The position and concentration of the carbon source reaching the surface of the substrate can be effectively adjusted by adjusting the gas flow of the carbon source introduced along the independent upper layer gas circuit or the lower layer gas circuit, so that the CBr during epitaxial growth can be adjusted₄Concentration profile of the source at the substrate surface.

Example 3

The method for improving the doping uniformity of the semiconductor laser provided by the embodiment of the invention is described by taking a vertical cavity surface emitting semiconductor laser as an example, wherein the vertical cavity surface emitting semiconductor laser is a 940nm vertical cavity surface emitting semiconductor laser.

First, the temperature uniformity of the substrate surface during epitaxial growth is adjusted. Specifically, silicon nitride can be deposited on the back of the gallium arsenide substrate by adopting a PECVD (plasma enhanced chemical vapor deposition) or LPCVD (low pressure chemical vapor deposition) process, the thickness of the deposited silicon nitride is 100 nm-2000 nm, the thermal expansion coefficient of the silicon nitride can be larger than that of the gallium arsenide substrate by adjusting the substrate parameters of the silicon nitride, when the gallium arsenide substrate is placed on a base of MOCVD (metal organic chemical vapor deposition) equipment to be heated, a silicon nitride film generates compressive strain, the gallium arsenide substrate becomes concave, and therefore the contact between the edge position of the gallium arsenide substrate and the base is poor, and the edge temperature is reduced; the temperature uniformity of the surface of the substrate can be effectively adjusted. In addition, the contact condition of the edge of the gallium arsenide substrate and the base can be changed by modifying the surface of the base into a convex shape under the condition that silicon nitride is not deposited, so that the effect of adjusting the temperature uniformity of the surface of the substrate is achieved.

Secondly, on the basis of adjusting the temperature uniformity of the surface of the substrate, the concentration distribution of the carbon tetrabromide doping source on the surface of the substrate during epitaxial growth can be adjusted. Specifically, the epitaxial growth process for the semiconductor laser can be realized according to the following steps: after the GaAs substrate was placed on the susceptor of the MOCVD apparatus and heated, as shown in FIG. 6, a GaAs buffer layer was grown to a thickness of 400nm and doped with Si to a concentration of 3e¹⁸/cm³(ii) a Introducing TMGa and AsH in the growth process₃And Si₂H₆(ii) a Growing an n-DBR, wherein the n-DBR comprises a mirror structure of 30-50 periods, each period comprising a single layer of AlGaAs component (Al component 10%, doped Si, concentration 3 e)¹⁸/cm³) Graded layer of AlGaAs composition (Al composition linearly graded from 10% to 90%, doped with Si, concentration 3 e)¹⁸/cm³) AlGaAs component monolayer (Al component 90%, doped Si, concentration 3 e)¹⁸/cm³) Graded layer of AlGaAs composition (Al composition linearly graded from 90% to 10%, doped with Si, concentration 3 e)¹⁸/cm³). TMGa, TMAl and AsH are introduced in the growth process₃And Si₂H₆(ii) a Growing an active layer comprising Al_0.28Ga_0.72As，InGaAs/GaAsP multiple quantum well structure, Al_0.28Ga_0.72As, and Al_0.98Ga_0.02An As oxide layer, and the like. Introducing TMIn, TMAl, TMGa and AsH in the growth process₃(ii) a Growing a p-DBR comprising a mirror structure of 10-30 periods, each period comprising a single layer of AlGaAs component (Al component 90%, doped with C, concentration 3 e)¹⁸/cm³) Graded layer of AlGaAs composition (Al composition linearly graded from 90% to 10%, doped with C, concentration 3 e)¹⁸/cm³) AlGaAs component monolayer (Al component 10%, doped C, concentration 3 e)¹⁸/cm³) Graded layer of AlGaAs composition (Al composition linearly graded from 10% to 90%, doped with C, concentration 3 e)¹⁸/cm³). Introducing TMAl, TMGa and AsH in the growth process₃And CBr₄。

For the doping source introduced in the epitaxial growth process, wherein, AsH₃Introducing TMIn, TMGa and TMAl from the middle layer gas path, CBr from the upper layer gas path and the lower layer gas path₄The gas circuit is introduced from the upper layer gas circuit and the middle layer gas circuit or from the middle layer gas circuit and the lower layer gas circuit or from the upper layer gas circuit, the middle layer gas circuit and the lower layer gas circuit. Specifically, when the doping sources are introduced, the corresponding doping sources are introduced from the corresponding gas circuits when each epitaxial layer is grown according to the doping sources required by the different epitaxial layers.

During the growth of the epitaxial layer, the MO sources (TMIn, TMGa and TMAl) are gradually consumed along the radial direction (diameter direction) of the substrate, while the group V source (AsH)₃) The total amount of the carbon source is kept basically constant, so that the V/III ratio (the ratio of the V-group doping source to the MO source flow) and the ratio of the MO source to the carbon source doping source are gradually changed along the radial direction of the substrate, the concentration of the carbon source along the radial direction of the substrate and the doping efficiency are continuously changed, and the concentration of the carbon finally incorporated into the epitaxial layer is also continuously changed along the radial direction of the substrate. In this example, two or three carbon sources are used. Because the gas flow heights of the carbon sources are different, the time for the two or three carbon sources to reach the surface of the substrate is different. The position and concentration of the carbon source reaching the surface of the substrate can be effectively adjusted by adjusting the air flow of the carbon source introduced along the independent upper layer air path or the lower layer air path, thereby adjusting the epitaxial growthTime CBr₄Concentration profile of the source at the substrate surface.

Although the present invention has been described in detail with respect to the exemplary embodiments and the advantages thereof, those skilled in the art will appreciate that various changes, substitutions and alterations can be made to the embodiments without departing from the spirit and scope of the invention as defined by the appended claims. For other examples, one of ordinary skill in the art will readily appreciate that the order of the process steps may be varied while maintaining the scope of the present invention.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.