CN113422293B - InGaN/GaN quantum well laser with stepped upper waveguide and preparation method thereof - Google Patents

InGaN/GaN quantum well laser with stepped upper waveguide and preparation method thereof Download PDF

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CN113422293B
CN113422293B CN202110688710.8A CN202110688710A CN113422293B CN 113422293 B CN113422293 B CN 113422293B CN 202110688710 A CN202110688710 A CN 202110688710A CN 113422293 B CN113422293 B CN 113422293B
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quantum well
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CN113422293A (en
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侯玉菲
赵德刚
梁锋
陈平
杨静
刘宗顺
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Institute of Semiconductors of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/2004—Confining in the direction perpendicular to the layer structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34333—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

An InGaN/GaN quantum well laser with a stepped upper waveguide, comprising: a lower waveguide layer; a multiple quantum well layer formed on the substrateA lower waveguide layer; and a stepped upper waveguide layer formed on the MQW layer; wherein the stepped upper waveguide layer comprises: in x Ga 1‑x N layer and In y Ga l‑y N layers; in x Ga 1‑x An N layer formed on the MQW layer, in y Ga l‑y An N layer formed on the In x Ga l‑x N layers; x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y. The invention can effectively increase the hole injection efficiency of the laser and simultaneously reduce the optical loss by regulating and controlling the energy band of the InGaN/GaN quantum well laser with the stepped upper waveguide, thereby improving the slope efficiency and the power conversion efficiency of the InGaN/GaN quantum well laser.

Description

InGaN/GaN quantum well laser with stepped upper waveguide and preparation method thereof
Technical Field
The invention relates to the technical field of gallium nitride-based semiconductor laser devices, in particular to an InGaN/GaN quantum well laser with a stepped upper waveguide and a preparation method thereof.
Background
The third generation GaN-based semiconductor material comprises gallium nitride (GaN), aluminum nitride (A1N), indium nitride (InN) and ternary and quaternary alloys thereof, and is an ideal material for preparing optoelectronic devices, especially lasers and Light Emitting Diodes (LEDs), due to stable chemical properties, high electron mobility, wide band gap adjustment range and strong corrosion resistance. The GaN-based semiconductor laser is a major breakthrough in the development history of lasers, has the advantages of small volume, high efficiency, long service life, fast response rate and the like, and is widely applied to the fields of biochemical medical treatment, ultraviolet curing, visible light communication, laser display, atomic clocks and the like, thereby being concerned by people.
However, gaN-based lasers require more complex structures to meet the photoelectric limit and high emission efficiency, with much less power conversion efficiency than GaN-based LEDs. The power conversion efficiency of the GaN-based LED reaches 80%, the power conversion efficiency of the GaN-based laser is lower than 40%, and the market expansion speed of the GaN-based semiconductor laser is inhibited by the low power conversion efficiency. The injection efficiency of carriers is an important factor affecting the power conversion efficiency of the laser. The P-type layer of the laser is generally doped with Mg, and the doping concentration is higher. In fact, mg doped p- (Al) GaN materials have greater ionization energy, and the ionization energy increases with increasing Al composition. The probability of magnesium atoms being ionized into free holes is very low, and most of the magnesium atoms form acceptor-bound holes, resulting in a low concentration of holes injected into the quantum well from the P-type layer. Moreover, the electron blocking layer in the laser blocks electrons and also blocks injection of holes. The low hole injection efficiency can reduce the probability of radiation recombination of electrons and holes in the quantum well, and the leakage of electrons is intensified, so that the non-radiation recombination rate of carriers is increased. In addition, another reason for low power conversion efficiency is high optical loss. The absorption coefficient of the Mg-doped P-type layer is large, and light distributed in the P-type layer is easily absorbed, resulting in an increase in optical loss inside the laser. Large optical losses reduce the slope efficiency and increase the threshold current, thereby reducing the power conversion efficiency of the laser.
Disclosure of Invention
In view of the above, the present invention is directed to an InGaN/GaN quantum well laser with a stepped upper waveguide and a method for fabricating the same, which are intended to at least partially solve at least one of the above-mentioned technical problems.
To achieve the above object, as one aspect of the present invention, there is provided an InGaN/GaN quantum well laser having a stepped upper waveguide, comprising: a lower waveguide layer; a multi-quantum well layer formed on the lower waveguide layer; and a stepped upper waveguide layer formed on the MQW layer; wherein the stepped upper waveguide layer comprises: in x Ga 1-x N layer and In y Ga 1-y N layers; in x Ga 1-x An N layer formed on the MQW layer, in y Ga 1-y An N layer formed on the In x Ga 1-x N layers; x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y.
As a second aspect of the present invention, there is provided a method for manufacturing the InGaN/GaN quantum well laser having a stepped upper waveguide as described above, comprising the steps of: manufacturing a lower waveguide layer;
manufacturing a multi-quantum well layer on the lower waveguide layer;
manufacturing a stepped upper waveguide layer on the multi-quantum well layer;
wherein, the step-shaped upper waveguide layer manufactured on the multiple quantum well layer comprises: forming In on the multiple quantum well layer x Ga 1-x N layers; in the In x Ga 1-x In is formed on the N layer y Ga 1-y And N layers, x and y respectively satisfy the following conditions: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y.
According to the technical scheme, the InGaN/GaN quantum well laser with the stepped upper waveguide and the preparation method have one or part of the following beneficial effects:
the InGaN/GaN quantum well laser adopts the step-shaped upper waveguide layer to replace the common upper waveguide layer, namely, the common upper waveguide layer is divided into In x Ga 1-x N layer and In y Ga 1-y N layer, it has the following advantage: the stepped upper waveguide layer regulates and controls the energy band of the laser structure by regulating the content of In, effectively reduces the accumulation of holes at the electron blocking layer, increases the hole concentration injected into the multiple quantum well layer, enables more carriers to participate In radiation recombination, and improves the power conversion efficiency of the laser; the stepped upper waveguide layer is unintentionally doped, and has low absorption coefficient, small light absorption and low optical loss; in addition, the In component In the stepped upper waveguide layer is adjusted, so that the refractive index difference between the waveguide layer and the multiple quantum well layer is increased, more optical fields are limited In the multiple quantum well layer, and the optical loss is reduced.
Drawings
FIG. 1 is a schematic diagram of an InGaN/GaN quantum well laser with a stepped upper waveguide in an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a stepped upper waveguide layer in an embodiment of the present invention;
fig. 3 is a power current relationship diagram of the novel InGaN/GaN quantum well violet laser with stepped upper waveguide and the violet laser with ordinary upper waveguide in the present invention.
Description of the reference numerals
1N model electrode
2. Substrate
3N type buffer layer
Model 4N lower confinement layer
5. Lower waveguide layer
6. Multiple quantum well layer
7. Stepped upper waveguide layer
7a In x Ga 1-x N layer
7b In y Ga 1-y N layer
8P type electron blocking layers
Model 9P upper confinement layer
10 P-type ohmic contact layer
11 P-type electrode
Detailed Description
In practicing the present invention, it was discovered that In an InGaN/GaN quantum well laser structure having a stepped upper waveguide, the upper waveguide layer of the structure utilizes In x Ga 1-x N layer and In y Ga 1-y The N layer replaces a common upper waveguide layer, so that the injection efficiency of a hole can be improved, the optical loss can be reduced, and the slope efficiency and the power conversion efficiency of the laser can be improved.
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
According to an embodiment of the present invention, there is provided an InGaN/GaN quantum well laser having a stepped upper waveguide, including: a lower waveguide layer; a multi-quantum well layer formed on the lower waveguide layer; and a stepped upper waveguide layer formed on the MQW layer;
wherein the stepped upper waveguide layer comprises: in (In) x Ga 1-x N layer and In y Ga 1-y N layer；In x Ga 1-x N layer formed on the MQW layer, in y Ga 1-y An N layer is formed on the In layer x Ga 1-x N layers; x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y.
The InGaN/GaN quantum well laser adopts the stepped upper waveguide layer to regulate and control the energy band, effectively reduces the obstruction of the electron barrier layer to hole transmission, improves the hole current density injected into the multiple quantum well layer, and improves the hole injection efficiency. In addition, the stepped upper waveguide layer is favorable for guiding the light field to approach to the InGaN/GaN quantum well, the light field distributed at the high-absorption P-type layer is reduced, and the optical loss is reduced, so that the threshold current and the slope efficiency are improved, and the InGaN/GaN quantum well laser with high photoelectric performance is obtained.
According to the embodiment of the invention, the total thickness of the step-shaped upper waveguide layer is 70-200nm x Ga 1-x The thickness of the N layer is 20-80nm, in y Ga 1-y The thickness of the N layer is 50-120 nm so as to guide a light field to approach the quantum well layer, reduce the light field distributed at the highly-absorbing P-type layer and reduce optical loss, thereby obtaining the InGaN/GaN quantum well violet laser with high photoelectric property.
According to an embodiment of the present invention, the InGaN/GaN quantum well laser having a stepped upper waveguide further includes: a substrate; the buffer layer is formed on one surface of the substrate; a first confinement layer formed on the buffer layer and located between the buffer layer and the lower waveguide layer; an electron blocking layer formed on the stepped upper waveguide layer; a second confinement layer formed on the electron blocking layer; an ohmic contact layer formed on the second confinement layer; a first electrode (N-type electrode) formed on the other surface of the substrate far from the buffer layer; and a second electrode (P-type electrode) formed on the ohmic contact layer.
According to an embodiment of the present invention, the substrate is a GaN substrate or a sapphire substrate; the thickness of the substrate is 50-170 μm.
According to the embodiment of the invention, the buffer layer is a GaN layer, an InGaN layer or an AlGaN layer, the buffer layer is doped with N type, the doping element is Si, and the doping concentration is 5 multiplied by 10 17 cm -3 ～9×10 18 cm -3 (ii) a The thickness of the buffer layer is 0.5-2.5 μm.
According to an embodiment of the present invention, the first confinement layer is N-doped Al a Ga 1-a N layer, a is more than or equal to 0 and less than or equal to 0.15, doping element is Si, and doping concentration is 5 multiplied by 10 17 cm -3 ～8×10 18 cm -3 (ii) a The thickness of the first confinement layer is 0.3 to 3 μm.
According to an embodiment of the present invention, the lower waveguide layer is In h Ga 1-h N layer or GaN layer, h is more than or equal to 0 and less than or equal to 0.02 h Ga 1-h The N layer or the GaN layer is doped or undoped in an N type, and when the lower waveguide layer is doped in an N type, the doped element is Si; the thickness of the lower waveguide layer is 50-150 nm.
According to an embodiment of the present invention, the multiple quantum well layer includes quantum well layers and quantum barrier layers alternately arranged.
According to an embodiment of the present invention, the quantum well layer is In b Ga 1-b B is more than or equal to 0.03 and less than or equal to 0.3, the number of quantum well layers is 2-5, and the single-layer thickness of each quantum well layer is 1.5-7 nm; the quantum barrier layers are GaN layers, the number of the quantum barrier layers is 3-6, the single-layer thickness of the quantum barrier layers is 10-15 nm, and the number of the quantum well layers is one less than that of the quantum barrier layers.
According to an embodiment of the present invention, the electron blocking layer is Al c Ga 1-c N layer or Al d In 1-d N layer, 0.1-0.3,0.75-d 0.95, P-type doping of the electron blocking layer, mg as doping element, and doping concentration of 1 × 10 19 cm -3 ～7×10 20 cm -3 (ii) a The thickness of the electron blocking layer is 10-30 nm.
According to an embodiment of the invention, the second confinement layer is Al e Ga 1-e N layer, e is more than or equal to 0.03 and less than or equal to 0.09, the second limiting layer is doped in P type, the doping element is Mg, and the doping concentration is 3 multiplied by 10 18 cm -3 ～8×10 19 cm -3 The thickness of the second limiting layer is 0.3-3 μm.
According to the embodiment of the invention, the ohmic contact layer is a GaN layer, the ohmic contact layer is doped in a P type, the doping element is Mg, and the doping concentration is 2 multiplied by 10 19 cm -3 ～3×10 20 cm -3 (ii) a The thickness of the ohmic contact layer is 0.07-0.25 μm.
According to an embodiment of the present invention, there is also provided a method for manufacturing the InGaN/GaN quantum well laser having the stepped upper waveguide, including the following steps: manufacturing a lower waveguide layer; manufacturing a multi-quantum well layer on the lower waveguide layer; manufacturing a stepped upper waveguide layer on the multi-quantum well layer; wherein, the step-shaped upper waveguide layer manufactured on the multiple quantum well layer comprises: in formation on MQW layer x Ga 1-x N layers; in x Ga 1-x In is formed on the N layer y Ga 1-y N layers, x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y.
According to the embodiment of the invention, the growth temperature of the upper waveguide layer is 700-1100 ℃.
According to an embodiment of the present invention, the above preparation method further includes: manufacturing a buffer layer on one surface of a substrate; manufacturing a first limiting layer on the buffer layer; manufacturing a lower waveguide layer on the first limiting layer; manufacturing an electron blocking layer on the stepped upper waveguide layer; manufacturing a second limiting layer on the electron blocking layer; manufacturing an ohmic contact layer on the second limiting layer; manufacturing a first electrode on the other surface of the substrate far away from the buffer layer; and manufacturing a second electrode on the ohmic contact layer.
According to an embodiment of the present invention, there is also specifically provided a method for manufacturing an InGaN/GaN quantum well laser, including the steps of:
step 1: reducing the substrate in a hydrogen atmosphere to clean the surface thereof;
step 2: with trimethyl gallium, trimethyl indium, trimethyl aluminium and ammonia (NH) 3 ) Respectively providing Ga, in, al and N sources for a precursor, and growing an N-type GaN, inGaN or AlGaN buffer layer on a substrate;
and step 3: h on the N-type buffer layer 2 As a carrier gas, growing an N-type A1GaN lower confinement layer (first confinement layer) at a high temperature;
and 4, step 4: h on the N-type AlGaN lower confinement layer 2 Or N 2 As carrier gas, epitaxially growing a GaN or InGaN lower waveguide layer;
and 5: growing InGaN/GaN multi-quantum well layer on GaN or InGaN lower waveguide layer at the same temperature of 700-900 ℃, wherein the quantum well layer is an InGaN layer, and N is used 2 As a carrier gas; the quantum barrier layer is a GaN layer and takes H 2 As a carrier gas;
and 6: epitaxially growing a stepped upper waveguide layer on the InGaN/GaN multi-quantum well layer at 700-1100 deg.C, specifically comprising growing In on the InGaN/GaN quantum well layer x Ga 1-x The N upper waveguide layer is 20-80 nm thick; in x Ga 1-x Growing In on the N upper waveguide layer y Ga 1-y The N upper waveguide layer has a thickness of 50-120nm, and x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y;
and 7: growing an A1GaN or AlInN electronic barrier layer on the stepped waveguide layer at high temperature by taking N2 as carrier gas;
and 8: h on AlGaN or AIInN electron blocking layer 2 As a carrier gas, a P-type AlGaN upper confinement layer (second confinement layer) is grown at a high temperature;
and step 9: h on the P-type AlGaN upper confinement layer 2 As carrier gas, growing a P-type GaN ohmic contact layer at high temperature;
step 10: evaporating an N-type electrode on the lower surface of the substrate by adopting a magnetron sputtering technology;
step 11: and (4) evaporating a P-type electrode on the upper surface of the P-type GaN ohmic contact layer by adopting a magnetron sputtering technology.
The technical solution of the present invention will be described in detail below with reference to specific examples. It should be noted that the following specific examples are only for illustration and are not intended to limit the invention.
Example 1
As shown in fig. 1, the InGaN/GaN quantum well laser with stepped upper waveguide grown by Metal Organic Chemical Vapor Deposition (MOCVD) includes: the semiconductor device comprises an N-type electrode 1, a substrate 2, an N-type buffer layer 3, an N-type lower limiting layer (first limiting layer) 4, a lower waveguide layer 5, a multi-quantum well layer 6, a stepped upper waveguide layer 7 (which is not intentionally doped), a P-type electron blocking layer 8, a P-type upper limiting layer (second limiting layer) 9, a P-type ohmic contact layer 10 and a P-type electrode 11.
The preparation method of the InGaN/GaN quantum well laser with the stepped upper waveguide comprises the following steps:
the N-type electrode 1 is Ti/Al/Ti/Au;
the substrate 2 is a GaN substrate with a thickness of 50 μm, and reduction treatment is performed on the substrate in a hydrogen atmosphere to clean the surface of the substrate; taking trimethyl gallium, trimethyl indium, trimethyl aluminum and ammonia (NH 3) as precursors, respectively providing Ga, in, al and N sources, growing an N-type buffer layer 3 on a substrate 2 at the growth temperature of 980 ℃, wherein the N-type buffer layer 3 is a GaN layer with the thickness of 2 mu m and the doping concentration of Si of 6 multiplied by 10 17 cm -3 ；
On the N-type buffer layer 3 with H 2 As a carrier gas, an N-type lower limiting layer is grown at high temperature, the N-type lower limiting layer is an AlGaN layer, the thickness of the AlGaN layer is 1.5 mu m, and the doping concentration of Si is 5 multiplied by 10 18 cm -3 The content of the Al component is 0.09;
on the N-type lower limiting layer 4 with N 2 As carrier gas, epitaxially growing a lower waveguide layer 5, the lower waveguide layer 5 being In h Ga 1-h The N layer is 100nm thick, the in component content is 0.012, and the N layer is not doped;
on the lower waveguide layer 5 with H 2 As a carrier gas, a multiple quantum well layer 6 was epitaxially grown at 900 deg.c, the multiple quantum well layer 6 being an InGaN/GaN layer In which two In were present b Ga 1-b N quantum well sandwiched between three GaN quantum barriers, in b Ga 1-b The In component of the N quantum well is 0.15, the thickness is 4.5nm, the number of well layers is 2, the thickness of the GaN quantum barrier is 13nm, and the number of well layers is 3;
growing an unintentionally doped stepped upper waveguide layer 7 on the multiple quantum well layer 6 at 700-1100 deg.C, wherein In is close to the quantum well x Ga 1-x The In component In the N layer is 0.025, the thickness is 60nm y Ga 1-y The In component In the N layer is 0.005, and the thickness is 110nm;
on the stepped upper waveguide layer 7 with H 2 As a carrier, growing a P-type electron blocking layer 8,P type electron blocking layer 8 at 1000 ℃ as an AlGaN electron blocking layer, wherein the Mg doping concentration is 7 multiplied by 10 20 cm -3 The thickness is 15nm;
h on the P-type electron blocking layer 8 2 As a carrier, a P type upper confinement layer 9 (second confinement layer) was grown at 1200 deg.C, the P type upper confinement layer 9 being an AlGaN upper confinement layer having a thickness of 0.55 μm, an Al component of 0.07, a Mg doping concentration of 3X 10 18 cm -3 ；
H on the P-type upper confinement layer 9 2 As a carrier, a P-type ohmic contact layer 10 was grown at 1100 deg.C, the P-type ohmic contact layer 10 was a GaN ohmic contact layer with a thickness of 0.12 μm and a Mg doping concentration of 3X 10 20 cm -3 ；
And (3) evaporating a P-type electrode 11 on the P-type ohmic contact layer 10 by adopting a magnetron sputtering technology, wherein the P-type electrode is made of Pd/Pt/Au materials, and the manufacturing of the InGaN/GaN quantum well laser is completed.
Fig. 2 is a schematic structural view of the stepped upper waveguide layer 7. The step-shaped upper waveguide layer contains In along the epitaxial growth direction x Ga 1-x N layer of 7a, in y Ga 1-y And an N layer 7b. Wherein the In composition of the InGaN layer 7a is 0.025 and the thickness is 60nm. In (In) y Ga 1-y The In composition of the N layer was 0.005 and the thickness was 110nm.
Fig. 3 is a graph showing the relationship between the power and current of the InGaN/GaN quantum well laser having the stepped upper waveguide and the laser having the conventional upper waveguide in this embodiment. As can be seen from fig. 3, the laser with the stepped upper waveguide has a lower threshold current and higher output power than the laser with the conventional upper waveguide (i.e., single-component InGaN upper waveguide), and the slope efficiency is significantly greater than that of the violet laser with the conventional upper waveguide.
It should also be noted that directional terms, such as "upper", "lower", "front", "rear", "left", "right", and the like, mentioned in the embodiments are only directions referring to the drawings, and are not intended to limit the scope of the present disclosure. Throughout the drawings, like elements are represented by like or similar reference numerals. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure. The shapes and dimensions of the components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.
Furthermore, the word "comprising" does not exclude the presence of materials or steps that do not act in the same or similar way as those listed in a claim. The word "a" or "an" preceding a structural element does not exclude the presence of multiple layers of structural elements having the same or similar function.
It should also be noted that unless steps are specifically described or must occur in sequence, the order of the steps is not limited to that listed above and may be varied or rearranged as desired. The embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e. technical features in different embodiments may be freely combined to form further embodiments.
The above-described embodiments of the present disclosure are not intended to limit the scope of the present disclosure. Any other corresponding changes and modifications made according to the technical idea of the present disclosure should be included in the protection scope of the claims of the present disclosure.

Claims (23)

1. An InGaN/GaN quantum well laser with a stepped upper waveguide, comprising:
a lower waveguide layer;
a multi-quantum well layer formed on the lower waveguide layer;
a stepped upper waveguide layer formed on the MQW layer; and
the electron blocking layer is formed on the stepped upper waveguide layer and is doped in a P type;
wherein the stepped upper waveguide layer comprises: in x Ga 1-x N layer and In y Ga 1-y N layers; in x Ga 1-x An N layer formed on the MQW layer, in y Ga 1-y An N layer formed on the In x Ga 1-x N layers; x and y respectively satisfy: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y;
the stepped upper waveguide layer is suitable for reducing the accumulation of holes at the electron barrier layer, increasing the hole concentration injected into the multiple quantum well layer, enabling more carriers to participate in radiation recombination, improving the power conversion efficiency of the InGaN/GaN laser, increasing the refractive index difference between the upper waveguide layer and the multiple quantum well layer, enabling more optical fields to be limited in the multiple quantum well layer, and accordingly reducing optical loss.
2. The InGaN/GaN quantum well laser of claim 1, wherein the total thickness of the stepped upper waveguide layer is 70 to 200nm;
said In x Ga 1-x The thickness of the N layer is 20-80 nm;
said In y Ga 1-y The thickness of the N layer is 50-120 nm.
3. The InGaN/GaN quantum well laser of claim 1, wherein the lower waveguide layer is In h Ga 1-h N layer or GaN layer, h is more than or equal to 0 and less than or equal to 0.02, in h Ga 1-h The N layer or the GaN layer is doped or undoped in an N type, and when the lower waveguide layer is doped in the N type, the doping element is Si.
4. The InGaN/GaN quantum well laser of claim 1, wherein the lower waveguide layer has a thickness of 50 to 150nm.
5. The InGaN/GaN quantum well laser of claim 1, wherein the InGaN/GaN quantum well laser further comprises:
a substrate;
the buffer layer is formed on one surface of the substrate;
a first confinement layer formed on the buffer layer and located between the buffer layer and the lower waveguide layer;
a second confinement layer formed on the electron blocking layer;
an ohmic contact layer formed on the second confinement layer;
the first electrode is formed on the other surface of the substrate far away from the buffer layer; and
and a second electrode formed on the ohmic contact layer.
6. The InGaN/GaN quantum well laser of claim 5, wherein the substrate is a GaN substrate or a sapphire substrate.
7. The InGaN/GaN quantum well laser of claim 5, wherein the substrate has a thickness of 50-170 μm.
8. The InGaN/GaN quantum well laser of claim 5, wherein the buffer layer is a GaN layer, an InGaN layer, or an AlGaN layer, the buffer layer is N-type doped, the doping element is Si, and the doping concentration is 5 x 10 17 cm -3 ～9×10 18 cm -3 。
9. The InGaN/GaN quantum well laser of claim 5, wherein the buffer layer has a thickness of 0.5-2.5 μm.
10. The InGaN/GaN quantum well laser of claim 5, wherein the electron blocking layer is Al c Ga 1-c N layer or Al d In 1-d N layer, 0.1-0.3,0.75-d 0.95, the doping element of the electron barrier layer is Mg, the doping concentration is 1 × 10 19 cm -3 ～7×10 20 cm -3 。
11. The InGaN/GaN quantum well laser of claim 5, wherein the electron blocking layer has a thickness of 10-30 nm.
12. The InGaN/GaN quantum well laser of claim 5, wherein the ohmic contact layer is a GaN layer, the ohmic contact layer is P-type doped, the doping element is Mg, and the doping concentration is 2 x 10 19 cm -3 ～3×10 20 cm -3 。
13. The InGaN/GaN quantum well laser of claim 5, wherein the ohmic contact layer has a thickness of 0.07 to 0.25 μm.
14. The InGaN/GaN quantum well laser of claim 5, wherein the first confinement layer is N-doped Al a Ga 1-a N layer, a is more than or equal to 0 and less than or equal to 0.15, doping element is Si, and doping concentration is 5 multiplied by 10 17 cm -3 ～8×10 18 cm -3 。
15. The InGaN/GaN quantum well laser of claim 5, wherein the first confinement layer has a thickness of 0.3-3 μm.
16. The InGaN/GaN quantum well laser of claim 5, wherein the second confinement layer is Al e Ga 1-e N layer, e is more than or equal to 0.03 and less than or equal to 0.09, the second limiting layer is doped in P type, the doping element is Mg, and the doping concentration is 3 multiplied by 10 18 cm -3 ～8×10 19 cm -3 。
17. The InGaN/GaN quantum well laser of claim 5, wherein the second confinement layer has a thickness of 0.3-3 μm.
18. The InGaN/GaN quantum well laser of claim 1, wherein the multiple quantum well layers comprise quantum well layers and quantum barrier layers alternately arranged.
19. The InGaN/GaN quantum well laser of claim 18, wherein the quantum well layer is In b Ga 1-b B is more than or equal to 0.03 and less than or equal to 0.3, the number of the quantum well layers is 2-5, and the single-layer thickness of each quantum well layer is 1.5-7 nm; the quantum barrier layers are GaN layers, the number of the quantum barrier layers is 3-6, the thickness of a single layer of the quantum barrier layers is 10-15 nm, and the number of the quantum well layers is one less than that of the quantum barrier layers.
20. A method of fabricating an InGaN/GaN quantum well laser with stepped upper waveguide according to any of claims 1 to 19, comprising the steps of:
manufacturing a lower waveguide layer;
manufacturing a multi-quantum well layer on the lower waveguide layer;
manufacturing a stepped upper waveguide layer on the multi-quantum well layer;
wherein, the step-shaped upper waveguide layer manufactured on the multiple quantum well layer comprises: forming In on the multiple quantum well layer x Ga 1-x N layers; in the In x Ga 1-x In is formed on the N layer y Ga 1-y And N layers, x and y respectively satisfy the following conditions: x is more than or equal to 0.01 and less than or equal to 0.1,0 and less than or equal to 0.015, and x is not equal to y.
21. The fabrication method according to claim 20, wherein the stepped upper waveguide layer is epitaxially fabricated on the mqw layer.
22. The process according to claim 20, wherein the growth temperature of the stepped upper waveguide layer is 700 to 1100 ℃.
23. The method of claim 20, further comprising:
manufacturing a buffer layer on one surface of a substrate;
manufacturing a first limiting layer on the buffer layer;
fabricating the lower waveguide layer on the first confinement layer;
manufacturing an electron blocking layer on the stepped upper waveguide layer;
manufacturing a second limiting layer on the electron blocking layer;
manufacturing an ohmic contact layer on the second limiting layer;
manufacturing a first electrode on the other surface of the substrate far away from the buffer layer;
and manufacturing a second electrode on the ohmic contact layer.
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