975 nm量子阱激光二极管的质子位移损伤

Proton Displacement Damage in 975 nm Quantum Well Laser Diodes

针对典型卫星轨道辐射环境下激光二极管(LD)的可靠性评估问题,对自研的975 nm GaAs基量子阱(QW)LD开展了10 MeV质子、3×10^(8)~3×10^(11)cm^(-2)注量的地面模拟辐照实验。结合蒙特卡罗软件仿真模拟和数学分析方法,全面研究了器件位移损伤退化规律,以及不同注量、不同辐照缺陷对器件功率特性、电压特性和波长特性等关键参数的影响。结果显示,质子辐照会引入非辐射复合中心等缺陷并破坏界面结构,导致载流子浓度降低、光电限制能力下降,宏观上体现为器件阈值电流增加、输出功率下降、波长红移和单色性受损。同时,3×10^(10)cm^(-2)以上注量的10 MeV质子等效位移损伤剂量辐照会对975 nm QW LD性能产生较大影响。

Objective The development of deep space exploration and interstellar flight technology imposes higher requirements on the performance of spacecraft,especially on the energy power system and wireless communication system.However,in the typical satellite orbit region in space,the environment is filled with huge numbers of highenergy particles,such as protons,electrons,and heavy ions,due to the strong impact of solar proton events,Van Allen radiation belts,and galactic cosmic rays.Consequently,spacecraft are always exposed to the threat of various radiation effects caused by highenergy radiation particles,resulting in storage errors,communication losses,attitude losses,and other problems.In serious cases,the flight mission may fail instantaneously.The highpower nearinfrared laser produced by the highpower 975 nm GaAsbased quantum well(QW)laser diode(LD)has outstanding advantages,such as high directivity,great monochromaticity,high optical power density,and long transmission distance.For this reason,such QW LDs have become the optimal choice to achieve longdistance wireless energy transmission and wireless communication in the complex space environment.Nevertheless,their development is seriously hindered by the harsh space environment and radiation effects.Therefore,to address the urgent need for major strategies in the radiation field,this paper studies the degradation law and triggering mechanism of highpower semiconductor QW LDs in radiation environments.Methods The accelerator is investigated by ground simulated irradiation experiment and simulation calculation and analysis.Specifically,regarding the current typical spacecraft orbit,the accumulated 10 MeV proton equivalent displacement damage dose(DDD)is calculated under the condition that the spacecraft has been in orbit for 10 years,and its value is between 3×10^(8) cm^(-2) and 3×10^(11) cm^(-2).Then,the 10 MeV proton irradiation experiment in vacuum at room temperature is carried out using the Beijing HI13 tandem accelerator,and the optical power,voltampere characteristics,and spectral performance of the LDs are tested before and after irradiation.Furthermore,Monte Carlo software simulation and theoretical calculation are performed to obtain the band structure and external differential quantum efficiency of the LDs before and after irradiation.The influence mechanism of material defects induced by proton irradiation and the changes in the interface and structure on the macroscopic performance of the LDs is analyzed in depth.Results and Discussions The restrictions on the photons and electrons in the highpower 975 nm GaAsbased QW LD come from the bandgap difference and the refractive index difference of the materials among the QW and the junction barriers on both sides.Monte Carlo software simulation reveals that protons can induce vacancy defects by detaching the lattice atoms in the component materials of the LD from the lattice points through elastic scattering or inelastic scattering.In this case,a peak defect density can also be observed at the interface of each epitaxial layer near the active region.The results of the irradiation experiments show that 10 MeV proton irradiation at a fluence higher than 3×10^(10) cm^(-2) has a great influence on the electrical and optical properties of the LD.In contrast,the effect of 10 MeV proton irradiation at a fluence below 3×10^(8) cm^(-2) on the electrical and optical properties of the LD is negligible.In addition,the degradation of the electrical and optical properties of the LD gradually aggravates as the accumulated proton fluence increases.As a result,macroscopic performance degradation phenomena can be observed,such as center wavelength shift,output power decline,threshold current increase,and voltampere characteristic deterioration.This indicates that more proton irradiation causes more severe performance degradation of the LD,ultimately resulting in more serious problems in stability and reliability.Conclusions This study presents selfdeveloped highpower 975 nm GaAsbased QW LDs and 10 MeV accelerator proton equivalent displacement damage irradiation experiments.The relationship between the performance degradation of the LD caused by the radiation effects and the accumulated proton fluence is analyzed by experimental tests and theoretical simulation methods,and the deep physical mechanism of the LD degradation induced by the radiation effects is clarified.The results suggest that the degree of the performance degradation of the LD as a result of the displacement damage effect is basically positively correlated with the accumulated fluence of proton irradiation,which causes severe performance degradation of the LD after a certain threshold is exceeded.Moreover,highfluence proton irradiation produces more interface defects,which further increase the probability of carrier scattering,affect carrier mobility,and ultimately reduce the ability of the QW structure to restrict the photons and electrons.The defects in the active region turn into nonradiative recombination centers.They lead to the increased nonradiative recombination inside the LD and decreased external differential quantum efficiency and ultimately cause the macroscopic performance degradation of the irradiated LDs,such as the center wavelength shift,decreased output power,increased threshold current,and deteriorated voltampere characteristics.This research is expected to provide a useful reference for the reliable selection,performance evaluation,and radiation hardening of the 975 nm GaAsbased QW LD and other similar optoelectronic devices before their application in radiation environments,as well as for the improved performance of the radiation hardening design.