Semiconductor laser element with current-induced self-polarization layer

Abstract

The invention relates to the technical field of lasers, and discloses a semiconductor laser element with a current-induced self-polarization layer, which sequentially comprises a substrate, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer and an upper limiting layer from bottom to top, a current-induced spin polarization layer is arranged between the electron blocking layer and the upper waveguide layer, and a current-induced spin polarization layer is arranged between the upper limiting layer and the electron blocking layer; and the current induction spin polarization layer is composed of a ReS2 / GeTe heterojunction or a ReS2 / GeTe / Cu2Te ternary superlattice. According to the invention, the current-induced spin polarization layer composed of the ReS2 / GeTe heterojunction or the ReS2 / GeTe / Cu2Te superlattice is arranged between the electron blocking layer and the upper waveguide layer and between the electron blocking layer and the upper limiting layer, so that current injection is dynamically responded when the laser works, and a spin polarization effect is generated.

Description

Technical Field

[0001] This invention relates to the field of lasers, and more specifically, to a semiconductor laser element having a current-induced self-polarization layer. Background Technology

[0002] Lasers are widely used in laser displays, laser TVs, laser projectors, communications, medical applications, weaponry, guidance, ranging, spectral analysis, cutting, precision welding, and high-density optical storage. There are many types of lasers, and they can be classified in various ways, mainly including solid-state, gas, liquid, semiconductor, and dye lasers. Compared with other types of lasers, all-solid-state semiconductor lasers have advantages such as small size, high efficiency, light weight, good stability, long lifespan, simple and compact structure, and miniaturization.

[0003] Existing technologies mitigate polarization effects by inserting undoped AlInGaN layers or layered structures, but these have limitations: Limited material: Only group III-V nitrides are used, which cannot produce spin polarization effect; Passive suppression: relies on material bandgap design and cannot dynamically respond to current injection; Limited application location: It only acts on the interface between the active region and the electron blocking layer.

[0004] Therefore, this invention proposes a semiconductor laser element with a current-induced spin polarization layer, which actively neutralizes multi-interface polarization fields under current drive through a current-induced spin polarization layer with a specific material combination (ReS2 / GeTe, etc.). Summary of the Invention

[0005] This invention provides a semiconductor laser element with a current-induced self-polarization layer, solving the technical problems in related technologies.

[0006] This invention provides a semiconductor laser element having a current-induced self-polarization layer, which, from bottom to top, comprises a substrate, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer, and an upper confinement layer. A current-induced spin polarization layer is provided between the electron blocking layer and the upper waveguide layer, and between the upper confinement layer and the electron blocking layer; The current-induced spin polarization layer is composed of a ReS2 / GeTe heterojunction or a ReS2 / GeTe / Cu2Te ternary superlattice; When current is injected into the laser, the layer generates a spin polarization effect along the current path, neutralizing the piezoelectric polarization field and spontaneous polarization field at the interface between the active layer and the electron blocking layer.

[0007] Furthermore, the thickness of the current-induced spin polarization layer is 20-100 nm.

[0008] Further, the thickness ratio of ReS2 and GeTe in the ReS2 / GeTe heterojunction is 1:1 to 1:3.

[0009] Further, when the self-polarization layer is a ReS2 / GeTe / Cu2Te ternary superlattice, it is composed of a plurality of period units, and each period unit contains a ReS2 layer, a GeTe layer and a Cu2Te layer.

[0010] Further, the Cu2Te layer is doped with Mn elements, and the doping concentration is 0.5%-2%.

[0011] Further, the active layer is an InGaN / AlGaN multi-quantum well structure, wherein the quantum well layer is In x Ga 1-x N, and the quantum barrier layer is Al y Ga 1-y N.

[0012] Further, the electron blocking layer is a p-type Al x Ga 1-x N layer, wherein the Al component x satisfies 0.2≤x≤0.4.

[0013] Further, the substrate is a magnesium aluminum spinel substrate or a sapphire / SiO2 / SiN x composite substrate.

[0014] Further, the first self-polarization layer is directly grown on the surface of the upper waveguide layer, and the second self-polarization layer is directly grown on the surface of the electron blocking layer.

[0015] Further, the ternary superlattice is grown by molecular beam epitaxy of the ReS2 layer and by atomic layer deposition of the GeTe / Cu2Te layer.

[0016] The beneficial effects of the present application are: The present application sets a current-induced spin polarization layer composed of a ReS2 / GeTe heterojunction or a ReS2 / GeTe / Cu2Te superlattice between the electron blocking layer and the upper waveguide layer and the upper confinement layer, which dynamically responds to current injection when the laser works, and generates a spin polarization effect. This effect can actively neutralize the piezoelectric / spontaneous polarization field at the interface of the active layer, the electron blocking layer and the waveguide layer, significantly alleviate the quantum confined Stark effect (QCSE), improve the electron-hole wave function overlap rate; at the same time, optimize the hole injection efficiency, reduce the device threshold current, improve the slope efficiency and high temperature stability. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of a semiconductor laser element provided with a current-induced self-polarization layer according to the present application; Figure 2is a flow chart of Embodiment 1 of the present application; Figure 3 is a flow chart of Embodiment 2 of the present application.

[0018] In the figure: 100, substrate; 101, lower confinement layer; 102, lower waveguide layer; 103, active layer; 104, upper waveguide layer; 105, electron blocking layer; 106, upper confinement layer; 107, current-induced spin polarization layer. DETAILED DESCRIPTION

[0019] The subject matter described herein will now be discussed with reference to example implementations. It should be understood that the discussion of these implementations is merely meant to provide a better understanding of the subject matter described herein and can be changed in ways not for departing from the scope of protection of the present specification. Various processes or components can be omitted, replaced or added according to needs of each example. In addition, features described with respect to some examples can also be combined in other examples.

[0020] Embodiment 1: ReS2 / GeTe heterojunction type spin polarization layer application As shown in Figure 1 and Figure 2 A semiconductor laser element provided with a current-induced self-polarization layer, from bottom to top, includes a substrate 100, a lower confinement layer 101, a lower waveguide layer 102, an active layer 103, an upper waveguide layer 104, an electron blocking layer 105, and an upper confinement layer 106; A current-induced spin polarization layer 107 is provided between the electron blocking layer 105 and the upper waveguide layer 104, and between the upper confinement layer 106 and the electron blocking layer 105; The current-induced spin polarization layer 107 is made of ReS2 / GeTe heterostructure; When the laser is injected with current, the layer produces a spin polarization effect along the current path direction, neutralizing the piezoelectric polarization field and spontaneous polarization field at the interface of the active layer 103 and the electron blocking layer 105.

[0021] The thickness of the current-induced spin polarization layer 107 is 20-100 nm.

[0022] The active layer 103 is an InGaN / AlGaN multi-quantum well structure, and the electron blocking layer 105 is a p-type AlGaN layer.

[0023] The substrate 100 is a magnesium aluminum spinel (MgAl2O4) substrate or a sapphire / SiO2 / SiN x composite substrate.

[0024] The thickness ratio of ReS2 to GeTe in the ReS2 / GeTe heterojunction is 1:1 to 1:3.

[0025] As Figure 2 shown, in one embodiment, specifically comprising the following steps: Step 1: Substrate pretreatment Take c-plane magnesium aluminate spinel (MgAl204) substrate (diameter 2 inches) Solvent cleaning: ultrasonic cleaning for 10 minutes by acetone, then ultrasonic cleaning for 10 minutes by isopropanol, and finally rinsing by deionized water; Annealing activation: Put into the MOCVD reaction chamber, and introduce high-purity nitrogen (flow rate 5 L / min); Ramp up to 850°C at 30°C / min, and keep for 15 minutes; Cool down naturally to the growth temperature; Step 2: Growth of lower confinement layer and waveguide layer (MOCVD) Growth of n-GaN lower confinement layer: Temperature: 1050°C; Precursor: TMGa (100 μmol / min) and NH3 (4 SLM); Doping: silane (SiH4) doping, concentration 1×10 19 cm -3 ; Thickness: 3 μm (growth rate 1.2 μm / h) Growth of GaN lower waveguide layer: Temperature: 1020°C; Precursor: TMGa (80 μmol / min) and NH3 (4 SLM); Thickness: 0.1 μm (undoped); Step 3: Growth of active layer (multi-quantum well) Quantum well (In 0.15 Ga 0.85 N well layer): Temperature: 760°C; Precursor: TMGa (10 μmol / min), TMIn (5 μmol / min), NH3 (6 SLM); Thickness: 3 nm (growth time 45 seconds) Quantum barrier (GaN barrier layer): Temperature: 870°C; Precursor: TMGa (30 μmol / min) + NH3 (30 μmol / min); Thickness: 8 nm (growth time 90 seconds); Repeat 5 cycles, total thickness 55 nm; Step 4: Growth of upper waveguide layer Temperature: 1020 °C; Precursors: TMGa (80 pmol / min) + NH3 (4 SLM); Thickness: 0.08 pm (un-doped); Step 5: Spin polarization layer deposition ReS2 layer (10 nm): Process: MOCVD low temperature growth; Temperature: 520 °C; Precursors: Rhenium source: Re(CO)5 (Pentacarbonyl rhenium), flow rate 5 seem; Sulfur source: H2S, flow rate 1000 seem (V / III ratio = 200); Pressure: 100 Torr; Growth time: 8 minutes (rate 1.25 nm / min); GeTe layer (20 nm): Process: Magnetron sputtering Target: GeTe alloy target (purity 99.999%); Atmosphere: Ar gas (flow rate 50 seem); Power: DC 150 W; Substrate temperature: 200 °C; Deposition rate: 10 nm / min (time 2 minutes); Step 6: Electron blocking layer and upper confinement layer growth p-Al 0.22 Ga 0.78 N electron blocking layer: Temperature: 1020 °C; Precursors: TMGa (50 pmol / min), TMAI (8 pmol / min), NH3 (4 SLM) Doping: Cp2Mg (dimethyl magnesium), concentration 5 x 10 18 cm -3 ; Thickness: 20 nm; p-GaN upper confinement layer: Temperature: 1020 °C; Precursors: TMGa (100 pmol / min) + NH3 (4 SLM); Doping: Cp2Mg (concentration 1 x 10 19 cm -3 ); Thickness: 0.5 pm; Step 7: Post-processing In-situ annealing: 800 °C for 5 minutes in N2 atmosphere, activating Mg doping; Wafer cleavage: Cleavage along the M-plane to form a 2000μm × 500μm laser bar; Electrode preparation: p-side: Ni / Au (10nm / 100nm) ring electrode; n-side: Ti / Al / Ti / Au (20nm / 200nm / 20nm / 100nm) total internal reflection electrode; In this embodiment, the substrate is a c-plane magnesium aluminum spinel (MgAl2O4) substrate, which is ultrasonically cleaned and then annealed with nitrogen (850℃ / 15min). The epitaxial structure is as follows: a 3 μm n-GaN lower confinement layer is grown from bottom to top (Si doping concentration 1×10⁻⁶). 19 cm -3 ), 0.1μm GaN underwaveguide layer, In 0.15 Ga 0.85 N / GaN multiple quantum well active layer (well / barrier thickness: 3nm / 8nm, 5 periods), 0.08μm GaN upper waveguide layer; Current-induced spin polarization layer: in the electron blocking layer (Al) 0.22 Ga 0.78 A ReS2 (10nm) / GeTe (20nm) heterojunction was inserted between the N (20nm thick) layer and the upper waveguide layer. The ReS2 layer was grown at a low temperature of 520℃ by MOCVD (precursors: Re(CO)5 and H2S), and the GeTe layer was deposited by sputtering (Ar gas flow rate 50sccm, power 150W). Upper structure: p-type Al 0.35 Ga 0.65 N electron blocking layer (Mg-doped 5×10⁻⁶) 18 cm -3 A 0.5 μm p-GaN confinement layer.

[0026] Performance testing: Electroluminescence testing: Injection current density 3kA / cm 2 At that time, the wavelength shift of the emission peak in the active region was only 2.1 nm (compared to 9.8 nm for the reference device without a spin polarization layer), and the QCSE effect was reduced by 78.6%. Power characteristics: Threshold current density reduced to 0.85 kA / cm² 2 (Reference device 1.28kA / cm) 2 The slope efficiency was improved by 41.3% (to 1.82 W / A).

[0027] Example 2: Application of ReS2 / GeTe / Cu2Te superlattice spin polarization layer like Figure 1 andFigure 3 As shown in the figure, a semiconductor laser element provided with a current-induced self-polarization layer comprises, from bottom to top, a substrate 100, a lower confinement layer 101, a lower waveguide layer 102, an active layer 103, an upper waveguide layer 104, an electron blocking layer 105, and an upper confinement layer 106; A current-induced spin polarization layer 107 is arranged between the electron blocking layer 105 and the upper waveguide layer 104, and between the upper confinement layer 106 and the electron blocking layer 105; The current-induced spin polarization layer 107 is composed of a ReS2 / GeTe / Cu2Te ternary superlattice; When the laser is injected with current, the layer generates a spin polarization effect along the direction of the current path, neutralizing the piezoelectric polarization field and the spontaneous polarization field at the interface between the active layer 103 and the electron blocking layer 105.

[0028] The thickness of the current-induced spin polarization layer 107 is 20-100 nm.

[0029] The active layer 103 is an InGaN / AlGaN multi-quantum well structure, and the electron blocking layer 105 is a p-type AlGaN layer.

[0030] The substrate 100 is a magnesium aluminum spinel (MgAl2O4) substrate or a sapphire / SiO2 / SiN x composite substrate.

[0031] As Figure 3 shown, in one embodiment, the method specifically comprises the following steps: Substrate loading: transferring the wafer grown with the GaN-upper waveguide layer 104 to the MBE-ALD interconnection system (vacuum transfer module pressure <1×10 -8 Torr) Step 1: MBE growth of the ReS2 layer (2 nm per cycle) Temperature rise: constant temperature at 400℃ (temperature rise rate 10℃ / min); Re beam: open the electron beam evaporation source, Re beam equivalent pressure 1×10 -7 Torr; S beam: cracking furnace temperature 800℃, S2 equivalent pressure 2×10 -6 Torr; Growth time: 20 minutes (rate 0.1 nm / min); Step 2: ALD deposition of the GeTe layer (3 nm per cycle) Temperature drop: constant temperature at 380℃ (N2 purge for 5 min); Precursor cycle: pass through a pulse of tetraisopropyl germane with a pulse time of 0.1 s, purge for 5 s, pass through N2 carrier gas purge for 3 s, and then pass through a pulse of bis-trimethyl tellurium with a pulse time of 0.2 s, purge for 8 s; Cycles: 27 (0.11 nm per growth) End point: Quartz crystal microbalance shows thickness of 3.0 ± 0.2 nm Step 3: Mn-doped Cu2Te layer deposition (2 nm per cycle) Maintain 380 °C Co-sputtering process: Targets: Cu2Te target (99.99%), Mn target (99.995%) Power: Cu2Te target 150 W RF, Mn target 15 W DC Ar pressure: 3 mTorr (flow 40 sccm) Rotating substrate: 30 rpm Thickness control: Sputtering rate 0.1 nm / s, total time 20 s Doping calibration: In-situ XPS monitoring of Mn2p peak (binding energy 641.2 eV) 3 / 2 Step 4: Superlattice cycle repetition Repeat steps 1 to 3 for a total of 5 cycles Inter-cycle treatment: Clean surface with H2 plasma (50 W, 30 s) at the end of each cycle Step 5: Electron blocking layer regrowth Vacuum transfer to MOCVD chamber (transfer time < 60 s) p-Al 0.3 Ga 0.7 N EBL: Temperature: 1000 °C Precursors: TMAl (8 pmol / min), TMGa (17 pmol / min), NH3 (3 SLM) Cp2Mg flow: 300 nmol / min (corresponding to 5 x 10 18 cm -3 ) Thickness: 25 nm (growth time 12 min) Step 6: Upper confinement layer completion p-GaN layer: 0.6 pm thick (grown at 1040 °C, rate 1.2 pm / h) Mg doping gradient: 1 x 10 20 cm -3 at the bottom to 5 x 10 19 cm -3 at the top p+-contact layer: 20 nm p + -GaN (grown at low temperature of 650 °C) ​Mg doping: 1.2 x 10 20 cm -3 (Cp2Mg flow 1.2 pmol / min); Step 7: In-situ annealing 700℃ annealing for 10 min under N2 atmosphere (heating / cooling rate 30℃ / min).

[0032] A ternary superlattice was set between the electron blocking layer (Al 0.3 Ga 0.7 N) and the upper confining layer (p-GaN): composed of 5 periods of [ReS2(2nm) / GeTe(3nm) / Cu2Te(2nm)] units (total thickness 35nm). The Cu2Te layer was doped with 1% Mn element to enhance the spin-orbit coupling effect; Growth control: ReS2 layer was grown by MBE (beam flux ratio Re:S = 1:20), GeTe / Cu2Te layers were deposited by atomic layer deposition (GeTe precursor: Ge(i-Pr)4 and Te(SiMe3)2, Cu2Te precursor: Cu(acac)2 and Te(SiMe3)2, temperature 380℃).

[0033] Band modulation effect: observed by Kelvin probe force microscopy (KPFM): the conduction band barrier at the interface of the electron blocking layer was reduced by 190 meV (compared to the reference device) when a current of 1.5 kA / cm 2 was injected; Hole injection efficiency: electrochemical capacitance voltage test showed that the hole concentration was increased by 3.2 times (up to 7.5 x 10 17 cm -3 ), and the device still maintained single-mode output at a high temperature of 80℃.

[0034] The above describes the embodiments of the present application, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative and not restrictive. Those skilled in the art can make many forms under the inspiration of the present application, which are all within the protection scope of the present application.

Claims

1. A semiconductor laser device provided with current-induced self-polarization layers, comprising, from bottom to top, a substrate (100), a lower confinement layer (101), a lower waveguide layer (102), an active layer (103), an upper waveguide layer (104), an electron blocking layer (105), and an upper confinement layer (106), characterized in that: each of the electron blocking layer (105) and the upper confinement layer (106) is provided with a current-induced spin polarization layer (107); the current-induced spin polarization layer (107) is composed of a ReS2 / GeTe heterojunction or a ReS2 / GeTe / Cu2Te ternary superlattice; when a current is injected into the laser, the layer generates a spin polarization effect along the direction of the current path, neutralizing the piezoelectric polarization field and the spontaneous polarization field at the interface between the active layer (103) and the electron blocking layer (105). The thickness of the current-induced spin polarization layer (107) is 20-100 nm. In the ReS2 / GeTe heterojunction, the thickness ratio of ReS2 to GeTe is 1:1 to 1:

3. When the self-polarization layer is a ReS2 / GeTe / Cu2Te ternary superlattice, it is composed of several period units, each of which contains a ReS2 layer, a GeTe layer, and a Cu2Te layer.

2. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The Cu2Te layer is doped with Mn elements, and the doping concentration is 0.5%-2%.

3. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The first self-polarization layer is directly grown on the surface of the upper waveguide layer (104), and the second self-polarization layer is directly grown on the surface of the electron blocking layer (105).

4. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The ternary superlattice is grown by molecular beam epitaxy to grow the ReS2 layer and by atomic layer deposition to grow the GeTe / Cu2Te layer.

5. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 4, characterized in that, ​ 6. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The active layer (103) is an InGaN / AlGaN multi-quantum well structure, wherein the quantum well layer is In x Ga 1-x N, and the quantum barrier layer is Al y Ga 1-y N.

7. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The electron blocking layer (105) is a p-type Al x Ga 1-x N layer, wherein the Al composition x satisfies 0.2 ≤ x ≤ 0.

4.

8. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, The substrate (100) is a magnesium-aluminum spinel substrate or sapphire / SiO2 / SiN x Composite substrate.

9. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 1, characterized in that, ​ 10. A semiconductor laser device provided with a current-induced self-polarization layer according to claim 4, characterized in that, ​

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