An edge-emitting semiconductor laser

Abstract

The application relates to the field of semiconductor technology and discloses an edge-emitting semiconductor laser, which comprises a substrate, a buffer layer, an N-type lower limiting layer, an N-type lower mode expansion layer, an N-type lower low-refractive layer, an N-type lower waveguide layer, a first barrier layer, a quantum well layer, a second barrier layer, a P-type upper waveguide layer, a P-type upper low-refractive layer, a P-type upper mode expansion layer, a P-type upper limiting layer and a cover layer which are sequentially arranged; the quantum well layer is made of InGaAs material, the first barrier layer and the second barrier layer are made of GaInP material; the N-type lower low-refractive layer and the P-type upper low-refractive layer are both made of Al 0.5 GaAs material, the N-type lower mode expansion layer and the P-type upper mode expansion layer are both made of Al 0.35 GaAs material. On the basis of a conventional InGaAs / GaAs quantum well structure, the application introduces GaInP material as a barrier to play a role of limiting electrons and strain buffering; and mode expansion layers and low-refractive layers are adopted to reduce a vertical divergence angle and a threshold current, so that the threshold current is prevented from rapidly rising with the reduction of the vertical divergence angle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor technology, and in particular to an edge-emitting semiconductor laser. BACKGROUND

[0002] With the rapid development of semiconductor optoelectronic devices, high-power semiconductor lasers have emerged. Due to the small size, low price, high electro-optical conversion efficiency and long service life of semiconductor lasers, semiconductor lasers have a very wide application in the field of optoelectronics. Semiconductor lasers are devices that produce laser light using certain semiconductor materials as working substances. The working principle is to achieve particle number inversion of non-equilibrium carriers between the energy bands (conduction band and valence band) of the semiconductor material or between the energy bands of the semiconductor material and the impurity (acceptor or donor) energy level through a certain excitation method. When a large number of electrons and holes in the particle number inversion state recombine, stimulated emission occurs.

[0003] The edge-emitting light-emitting laser is called an edge-emitting laser, and its light-emitting area is limited to a small part on one side. The limited light-emitting area can improve the coupling efficiency with optical fibers and integrated optical circuits. In its semiconductor material, InGaAs has the characteristics of narrow bandwidth, few recombination centers, and high carrier mobility, and is the first choice for preparing high-speed microelectronic materials and devices, especially in sensors, detectors, and optical fiber communication, which has broad development space and application prospects. The current edge-emitting laser generally uses InGaAs / GaAs or InGaAs / AlGaAs quantum well structure system, but this structure system will produce a large number of defects during epitaxial growth due to lattice mismatch, and the In component and the thickness of the epitaxial layer that can be grown are limited, which limits the improvement of device performance.

[0004] In addition, the edge-emitting semiconductor laser has a very large vertical divergence angle, which makes the far-field light spot of the laser elliptical, which reduces the pumping efficiency and fiber coupling efficiency. Therefore, reducing the vertical divergence angle of the semiconductor laser can expand its application range, which has important practical significance. The current methods for reducing the vertical divergence angle generally include narrow waveguide structure, large optical cavity wide waveguide structure, asymmetric waveguide, and mode expansion layer structure. However, these methods will cause the reduction of the device confinement factor, thereby greatly increasing the threshold current of the laser. Moreover, the above-mentioned methods for reducing the vertical divergence angle can only reduce the divergence angle of the laser to about 20°, and will encounter the bottleneck of process difficulty or threshold current increase, which lacks practical application value. SUMMARY

[0005] Therefore, the present application aims to provide an edge-emitting semiconductor laser, which introduces GaInP material as a potential barrier to limit electrons and strain buffer on the basis of a conventional InGaAs / GaAs quantum well structure, and uses a mode expansion layer and a low refractive index layer to reduce a vertical divergence angle and a threshold current, thereby avoiding rapid rise of the threshold current with reduction of the vertical divergence angle.

[0006] The present application solves the above technical problems by the following technical means:

[0007] An edge-emitting semiconductor laser comprises a substrate, wherein a buffer layer, an N-type lower limiting layer, an N-type lower mode expansion layer, an N-type lower low refractive index layer, an N-type lower waveguide layer, a first potential barrier layer, a quantum well layer, a second potential barrier layer, a P-type upper waveguide layer, a P-type upper low refractive index layer, a P-type upper mode expansion layer, a P-type upper limiting layer and a cover layer are sequentially arranged on the substrate from bottom to top; the quantum well layer is made of InGaAs material, the first potential barrier layer and the second potential barrier layer are made of GaInP material; the N-type lower low refractive index layer and the P-type upper low refractive index layer are both made of AlGaAs material; the N-type lower mode expansion layer and the P-type upper mode expansion layer are both made of AlGaAs material. 0.5 0.35 GaAs material.

[0008] In the present application, from the perspective of lattice mismatch, the lattice constant of GaAs is , the lattice constant of GaInP ranges from , the lattice constant of InGaAs ranges from , the lattice constant of GaInP enables it to be used as a strain buffer layer between InGaAs and bulk material, and in the case of ensuring In component in the quantum well, the lattice constant of the whole structure presents a gradual change trend, thereby relieving the compressive strain introduced by InGaAs quantum well in the case of high In component, reducing defects caused by the strain, improving growth quality and threshold characteristics of the structure.

[0009] From the perspective of energy band, the band gap of GaInP is much larger than that of GaAs; the energy band width of GaAs is 1.42eV, the band gap of AlGaAs in the case of direct band gap ranges from 1.42eV to 1.99eV; the band gap width of GaInP ranges from 1.35eV to 2.78eV, which is much larger than that of GaAs and AlGaAs in the case of direct band gap, so that the use of GaInP as the potential barrier of the quantum well structure can more effectively limit electrons, thereby improving the efficiency of the device. Meanwhile, the use of GaInP instead of AlGaAs can avoid oxidation of Al component, reduce the difficulty of epitaxial growth and improve the service life of the device.

[0010] ​The low refractive index layer and the mode expansion layer can both expand the near-field light field to reduce the vertical divergence angle. The difference is that the low refractive index layer can expand the near-field light field while improving the confinement factor of the laser, and the mode expansion layer reduces the confinement factor of the laser as the divergence angle decreases.

[0011] Further, the thickness of the quantum well layer is 4-6nm, the In component of the InGaAs material is 0.35, and the Ga component is 0.65; the thickness of the first barrier layer and the second barrier layer is 40-60nm, the GaInP material is undoped, and the Ga component is 0.37 and the In component is 0.63. The components and thicknesses of the materials can meet the requirements of high gain.

[0012] Further, the thickness of the N-type lower low refractive index layer is 550-650nm, the Al 0.5 The GaAs material is N-type Si doped, and the doping concentration is 1.0e18; the thickness of the P-type upper low refractive index layer is 550-650nm, the Al 0.5 The GaAs material is P-type Zn doped, and the doping concentration is 8.0e17.

[0013] Further, the thickness of the N-type lower mode expansion layer is 350-450nm, the Al 0.35 The GaAs material is N-type Si doped, and the doping concentration is 1.0e18; the thickness of the P-type upper mode expansion layer is 250-350nm, the Al 0.35 The GaAs material is P-type Zn doped, and the doping concentration is 8.0e17.

[0014] In this way, the lower low refractive index layer and the mode expansion layer have a certain refractive index difference, which is more conducive to the propagation of light in the present scheme, and both are doped to reduce resistance while not causing large-scale scattering of light.

[0015] Further, the thickness of the buffer layer is 150-250nm, the GaAs material is N-type Si doped, and the doping concentration is 2e18.

[0016] Further, the thickness of the cap layer is 150-250nm, the GaAs material is P-type Zn doped, and the doping concentration is 3e19.

[0017] Further, the thickness of the N-type lower confinement layer is 1100-1300nm, the In 0.48 Ga 0.52 N 0.05 P 0.95, N type Si doping, doping concentration gradually changes from 8.0e17 to 2.7e17 from bottom to top; the thickness of the P type upper confining layer is 700-800nm, Al 0.41 GaAs material, P type Zn doping, doping concentration is 7e17.

[0018] The rare nitrogen material In 0.48 Ga 0.52 N 0.05 P 0.95 As a lower confining layer, the material growth process and characterization means are mature, when the component of In is 0.48, the lattice constant is matched with GaAs, and metal organic vapor phase epitaxy (MOCVD) can be directly grown; through the rare nitrogen In 0.48 Ga 0.52 N 0.05 P 0.95 Material component change of N element, by controlling the energy band structure between it and the GaAs transition layer, the carrier energy loss occurring at the two interfaces can be reduced, so as to reduce the voltage loss of device operation and improve the efficiency of the device.

[0019] Further, the thickness of the N type lower waveguide layer is 150-250nm, AlGaAs material is adopted, the Al component of the AlGaAs material gradually changes from 0.37 to 0.22 from bottom to top, N type Si doping, doping concentration is 5e16; the thickness of the P type upper waveguide layer is 300-400nm, AlGaAs material is adopted, the Al component of the AlGaAs material gradually changes from 0.22 to 0.41 from bottom to top, P type Zn doping, doping concentration is 5e16.

[0020] Further, the substrate adopts (100) bias <111> N type GaAs material. The substrate is used for epitaxially growing each layer of the laser material thereon.

[0021] The beneficial effects of the present application are as follows:

[0022] 1, the In 0.35 Ga 0.65 As / Ga 0.37 In 0.63 P material growth and characterization means are mature and diverse, solve the defect problem caused by lattice mismatch between materials, reduce the threshold, and the Ga 0.37 In 0.63 P band gap width is large, which ensures the restriction of electrons and strain buffer effect, and increases the efficiency.

[0023] 2, the introduction of the mode expansion layer and the low refractive index layer can reduce the vertical divergence angle while considering the threshold current, so as to avoid the rapid rise of the threshold current with the reduction of the vertical divergence angle.

[0024] 3、the rare nitrogen material In 0.48 Ga 0.52 N 0.05 P 0.95 As a N-type lower confinement layer, energy loss in the process of electron or hole transmission can be reduced, voltage loss of the structure is reduced, and thus efficiency of the final device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural schematic diagram of an edge-emitting semiconductor laser of the present application;

[0026] The substrate 1, the buffer layer 2, the N-type lower confinement layer 3, the N-type lower mode expansion layer 4, the N-type lower low-refractive layer 5, the N-type lower waveguide layer 6, the first barrier layer 7, the quantum well layer 8, the second barrier layer 9, the P-type upper waveguide layer 10, the P-type upper low-refractive layer 11, the P-type upper mode expansion layer 12, the P-type upper confinement layer 13, and the cap layer 14 are sequentially arranged from bottom to top. DETAILED DESCRIPTION

[0027] The present application will be described in detail below with reference to the accompanying drawings:

[0028] As Figure 1 shown:

[0029] The edge-emitting semiconductor laser provided in the embodiment includes 14 layers from bottom to top, and specifically as follows:

[0030] The first layer is a substrate, which is an N-type GaAs substrate with a (100) bias <111> surface. The substrate is used for epitaxial growth of materials of each layer of the laser thereon.

[0031] The second layer is a GaAs buffer layer with a thickness of 150-250 nm, 200 nm in the embodiment, and N-type Si doping with a doping concentration of 2e18.

[0032] The third layer is an N-type lower confinement layer, which is a rare N material In 0.48 Ga 0.52 N 0.05 P 0.95 with a thickness of 1100-1300 nm, 1200 nm in the embodiment, and N-type Si doping with a concentration gradually changing from 8.0e17 to 2.7e17 from bottom to top.

[0033] The fourth layer is an N-type lower mode expansion layer, which is an Al 0.35 GaAs material with a thickness of 350-450 nm, 400 nm in the embodiment, and N-type Si doping with a concentration of 1.0e18.

[0034] The fifth layer is an N-type lower low-refractive layer, which is an Al 0.5GaAs material, thickness of 550-650nm, 600nm in this embodiment, N-type Si doped, doping concentration of 1.0e18;

[0035] Layer 6, N-type lower waveguide layer, AlGaAs material, thickness of 150-250nm, 200nm in this embodiment, N-type Si doped, doping concentration of 5e16, wherein Al component gradually changes from 0.37 to 0.22 from bottom to top;

[0036] Layer 7, first barrier layer, GaInP material, thickness of 40-60nm, 50nm in this embodiment, wherein Ga component is 0.37 and In component is 0.63, no doping;

[0037] Layer 8, quantum well layer, In 0.35 Ga 0.65 As material, thickness of 4-6nm, 5nm in this embodiment, In 0.35 Ga 0.65 As material with this thickness can meet the requirement of high gain;

[0038] Layer 9, second barrier layer, GaInP material, thickness of 40-60nm, 50nm in this embodiment, wherein Ga component is 0.37 and In component is 0.63, no doping;

[0039] Layer 10, P-type upper waveguide layer, AlGaAs material, thickness of 300-400nm, 350nm in this embodiment, P-type Zn doped, doping concentration of 5e16, wherein Al component gradually changes from 0.22 to 0.41 from bottom to top;

[0040] Layer 11, P-type upper low refractive index layer, Al 0.5 GaAs material, thickness of 550-650nm, 600nm in this embodiment, P-type Zn doped, concentration of 8.0e17;

[0041] Layer 12, P-type upper mode expansion layer, Al 0.35 GaAs material, thickness of 250-350nm, 300nm in this embodiment, P-type Zn doped, concentration of 8.0e17;

[0042] Layer 13, P-type upper confinement layer, Al 0.41 GaAs material, thickness of 700-800nm, 750nm in this embodiment, P-type Zn doped, doping concentration of 7e17;

[0043] Layer 14, GaAs cap layer, thickness of 150-250nm, 200nm in this embodiment, P-type Zn doped, doping concentration of 3e19.

[0044] The structure of the edge-emitting semiconductor laser can refer to the following table:

[0045] Structure Material Thickness (nm) Doping / concentration (cm -3 ) Cap layer GaAs 200 Zn-doped / 3.0e19 P-type upper confinement layer Al 0.41 GaAs 750 Zn-doped / 7.0e17 P-type upper mode expansion layer Al 0.35 GaAs 300 Zn-doped / 8.0e17 P-type upper low refractive index layer Al 0.50 GaAs 600 Zn-doped / 8.0e17 P-type upper waveguide layer Al 0.22～0.41 GaAs 350 Zn-doped / 5.0e16 Barrier layer Ga 0.37 InP 50 --- Quantum well In 0.35 Ga 0.65 As]]> 5 --- Barrier layer Ga 0.37 InP 50 --- N-type lower waveguide layer Al 0.37～0.22 GaAs 200 Si-doped / 5.0e16 N-type lower low refractive index layer Al 0.50 GaAs 600 Si-doped / 1.0e18 N-type lower mode expansion layer Al 0.35 GaAs 400 Si-doped / 1.0e18 N-type lower confinement layer In 0.48 Ga 0.52 N 0.05 P 0.95 ]]> 1200 Si-doped / 8.0e17 ~ 2.7e17 Buffer layer GaAs 200 Si-doped / 2e18 Substrate N-type GaAs (100) off <111> --- ---

[0046] The edge-emitting semiconductor laser of the embodiment selects In 0.35 Ga 0.65 As / Ga 0.37 In 0.63 P material growth and characterization means are mature and diverse, which solves the defect problem caused by lattice mismatch between materials, reduces the threshold, and the potential barrier material Ga 0.37 In 0.63 P has a wide band gap, which ensures the restriction of electrons and increases the efficiency.

[0047] The selected rare nitrogen In 0.48 Ga 0.52 N 0.05 P 0.95 material growth process and characterization means are mature, when the component of In is 0.48, the lattice constant is matched with GaAs, and metal organic vapor phase epitaxy technology can be directly grown. Through the rare nitrogen In 0.48 Ga 0.52 N 0.05 P 0.95 material, the component change of N element can control the energy band structure between it and GaAs, reduce the carrier energy loss occurring on the two interfaces, and thus reduce the voltage loss.

[0048] In the embodiment, a low refractive index layer and a mode expansion layer are also provided, and the low refractive index layer and the mode expansion layer can both expand the near-field light field and thus reduce the vertical divergence angle; the difference is that the low refractive index layer can improve the confinement factor of the laser while expanding the near-field light field, and the mode expansion layer reduces the confinement factor of the laser as the divergence angle decreases.

[0049] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the present application, and all should be covered in the scope of the claims of the present application. The technical, shape and structure parts not described in detail in the present application are well-known technologies.

Claims

1. A side-emitting semiconductor laser, comprising a substrate, characterized in that: A buffer layer, an N-type lower confinement layer, an N-type lower mode extension layer, an N-type lower low-refractive-index layer, an N-type lower waveguide layer, a first barrier layer, a quantum well layer, a second barrier layer, a P-type upper waveguide layer, a P-type upper low-refractive-index layer, a P-type upper mode extension layer, a P-type upper confinement layer, and a capping layer are sequentially disposed on the substrate from bottom to top. The quantum well layer is made of InGaAs material, and the first and second barrier layers are made of GaInP material. Both the N-type lower low-refractive-index layer and the P-type upper low-refractive-index layer are made of Al. 0.5 GaAs material, both the N-type lower mode extension layer and the P-type upper mode extension layer are made of Al. 0.35 GaAs materials; The quantum well layer has a thickness of 4-6 nm, with an In composition of 0.35 and a Ga composition of 0.65 in the InGaAs material; the first and second barrier layers both have a thickness of 40-60 nm, with undoped GaInP material having a Ga composition of 0.37 and an In composition of 0.63; the N-type lower low-refractive-index layer has a thickness of 550-650 nm, and the Al... 0.5 The GaAs material is N-type Si-doped with a doping concentration of 1.0e18; the thickness of the low-refractive-index layer on the P-type substrate is 550-650 nm; the Al... 0.5 The GaAs material is p-type Zn-doped with a doping concentration of 8.0e17; the thickness of the N-type lower confinement layer is 1100-1300 nm, and it is made of rare N material In. 0.48 Ga 0.52 N 0.05 P 0.95 The Si is N-type doped, with the doping concentration gradually increasing from 8.0e17 to 2.7e17 from bottom to top.

2. The edge-emitting semiconductor laser according to claim 1, characterized in that: The thickness of the N-type lower mode extension layer is 350-450 nm, using Al. 0.35 GaAs material, N-type Si doped, with a doping concentration of 1.0e18; the thickness of the P-type upper mode extension layer is 250-350 nm, using Al 0.35 GaAs material, p-type Zn doped, with a doping concentration of 8.0e17.

3. The edge-emitting semiconductor laser according to claim 2, characterized in that: The thickness of the buffer layer is 150-250 nm, and it is made of GaAs material with N-type Si doping and a doping concentration of 2e18.

4. A side-emitting semiconductor laser according to claim 2, characterized in that: The capping layer has a thickness of 150-250 nm, is made of GaAs material, is p-type Zn doped, and has a doping concentration of 3e19.

5. A side-emitting semiconductor laser according to claim 3 or 4, characterized in that: The thickness of the P-type upper confinement layer is 700-800 nm, and it uses Al. 0.41 GaAs material, P-type Zn doped, with a doping concentration of 7e17.

6. A side-emitting semiconductor laser according to claim 5, characterized in that: The thickness of the N-type lower waveguide layer is 150-250 nm, and it is made of AlGaAs material. The Al composition of the AlGaAs material gradually changes from 0.37 to 0.22 from bottom to top. It is N-type Si doped with a doping concentration of 5e16. The thickness of the P-type upper waveguide layer is 300-400 nm, and it is made of AlGaAs material. The Al composition of the AlGaAs material gradually changes from 0.22 to 0.41 from bottom to top. It is P-type Zn doped with a doping concentration of 5e16.

7. A side-emitting semiconductor laser according to claim 3 or 4, characterized in that: The substrate is (100) biased <111> N-type GaAs material with a surface.

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