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采用SiLENSe (Simulator of Light Emitters based on Nitride Semiconductors)仿真软件进行理论仿真实验。InGaN基绿光LD的外延结构如图1所示,其外延参数如表1所示。文中将优化下n侧InxGa1−xN层波导铟组分,取值0.04、0.05、0.06、0.07和0.075,其他结构参数都相同。通过改变n-InxGa1−xN波导层铟组分实现调控LD的光场分布。对LD器件结构进行模拟,设置偏压3~12 V,腔长800 μm,宽度10 μm,在设计材料时外延层的电子和空穴的迁移率分别为200 cm2V−1s−1和20 cm2V−1s−1,带偏移比ΔEc/ΔEv=0.7/0.3,俄歇系数(CP和Cn) InN为2.5×10−30 cm6s−1,GaN为0 cm6s−1,电子和空穴的非辐射寿命为0 s。激光器器件的光电性能都是在工作温度为300 K时计算获得,整个外延结构中每层的缺陷密度为1×106 cm−2。
表 1 InGaN基绿光LD的外延参数
Table 1. Structural parameters of InGaN-based green laser diode
Name Thickness Concentration
/cm−3Mobility
/cm2V−1s−1p-Contact layer 100 nm p-GaN 1×1020 200/20 p-Cladding layer (CL) 500 nm p-Al0.12In0.01Ga0.87N 1×1020 200/20 p-
Waveguide layer (WG)70 nm p-In0.04Ga0.96N 2×1019 200/20
Electron blocking layer (EBL)14nm p-Al0.18In0.01Ga0.81N 5×1018 200/20
Quantum well (QW)/
Quantum barrier
(QB) (×2)3.5 nm In0.29Ga0.71N/11 nm Al0.05In0.01Ga0.94N 0/6×1018 3000/30/
200/20QW 3.5 nm In0.29Ga0.71N 0 3000/30 n-WG 47.5 nm InxGa1-xN 5×1018 200/20 n-WG 100 nm n-GaN 5×1018 200/20 n-CL 550 nm n-Al0..09In0.01Ga0.9N 6×1018 200/20 n-Contact layer 100 nm n-GaN 6×1018 200/20
Influence of indium composition of n waveguide layer on photoelectric performance of GaN-based green laser diode
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摘要: 高功率GaN基激光二极管外延结构理论仿真对提高GaN基激光二极管的光电性能具有重要的指导意义。设计了一种n侧双波导结构的绿光激光二极管外延结构,讨论了激光器外延结构中n-InxGa1−xN波导层中铟组分对其光电性能的影响,揭示了n-InxGa1−xN波导层对激光二极管光电性能的影响机制。通过调控n-InxGa1−xN波导层中铟组分,调控外延层中的光场分布,使光场发生了偏移。结果表明,当n侧InxGa1−xN波导层中铟组分最佳值为0.07时,将光子损耗降低了0.2 cm−1,阈值电流由193.49 mA降低到115.98 mA,此外,器件的光子损耗最少,阈值电流最小,工作电压最低,从而提高了激光二极管的输出功率和电光转换效率。因此,当绿光激光二极管的注入电流密度为6 kA/cm2时,功率输出达234.95 mW。n侧双波导结构设计为制备高功率绿光激光二极管提供了理论指导和数据支撑。Abstract: The theoretical simulation of the extension structure of high-power GaN-based laser diodes is of great significance to improve the photoelectric performance of GaN-based laser diodes. A green laser diode extension structure with an n-side dual-wave conductor structure was designed. The effect of indium parts in the n-InxGa1−xN waveguide layer on its photoelectronic performance in laser extension structure was discussed. And the mechanism of the n-InxGa1−xN waveguide layer on the photoelectronic performance of laser diode was clarified. The results showed that when the indium part of the n-side InxGa1−xN waveguide layer was 0.07, the photon loss was minimal, and the threshold current was the lowest. When the indium part of the n-side waveguide layer was high or low, photon loss and operating voltage were increased, and meanwhile, the output power of the laser diode was reduced. Therefore, by regulating indium parts in the n-InxGa1−xN waveguide layer and controlling the optical field distribution of the outer layer, the photon loss was reduced by 0.2 cm−1, and the threshold current was reduced by 193.49 mA to 115.98 mA, and the operating voltage was reduced, which increased the output power and electro-optical conversion efficiency of the laser diode, increased the laser output power to 234.95 mW at 6 kA/cm2. The n-side dual-waveguide structure design provides theoretical guidance and data support for the preparation of high-power green laser diodes.
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Key words:
- green light /
- GaN based laser diode /
- waveguide layer /
- optical field distribution
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图 4 不同n-InxGa1-xN波导层铟组分下LD的多个量子阱外(αout) (a)、内(αQW) (b)和总光损耗(αTotal) (c)随注入电流的变化曲线(箭头所指0.5 A即6 kA/cm2)
Figure 4. Optical loss outside multiple quantum wells ( αout) (a), optical loss in multiple quantum wells (αQW) (b) and total optical loss (αTotal) (c) of laser diode versus the injected current for different n-InxGa1−xN waveguide indium content (The arrow indicates 0.5 A or 6 kA/cm2)
图 7 不同n-InxGa1−xN波导层铟组分下,LD的非辐射电流密度(a)、SRH电流密度(b)、俄歇电流密度(c)和有源区载流子浓度(d)与注入电流的关系
Figure 7. Curves of nonradiative current density (a), SRH current density (b), Auger current density (c) and active region carrier concentration (d) versus injected current at different indium components of n-InxGa1−xN waveguide layers
表 1 InGaN基绿光LD的外延参数
Table 1. Structural parameters of InGaN-based green laser diode
Name Thickness Concentration
/cm−3Mobility
/cm2V−1s−1p-Contact layer 100 nm p-GaN 1×1020 200/20 p-Cladding layer (CL) 500 nm p-Al0.12In0.01Ga0.87N 1×1020 200/20 p-
Waveguide layer (WG)70 nm p-In0.04Ga0.96N 2×1019 200/20
Electron blocking layer (EBL)14nm p-Al0.18In0.01Ga0.81N 5×1018 200/20
Quantum well (QW)/
Quantum barrier
(QB) (×2)3.5 nm In0.29Ga0.71N/11 nm Al0.05In0.01Ga0.94N 0/6×1018 3000/30/
200/20QW 3.5 nm In0.29Ga0.71N 0 3000/30 n-WG 47.5 nm InxGa1-xN 5×1018 200/20 n-WG 100 nm n-GaN 5×1018 200/20 n-CL 550 nm n-Al0..09In0.01Ga0.9N 6×1018 200/20 n-Contact layer 100 nm n-GaN 6×1018 200/20 -
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