Gamma-Irradiation Damage Mechanism Of InGaAs Infrared Photodetector Investigated By Photoluminescence

InGaAs infrared photodetectors（IR-PDs）,with advantages of low dark current,high detectivity,mature fabrication techniques and room-temperature operation,are extensively employed in the space and nuclear fields.Since the devices utilized in radiation environments typically experience degradation and even failure,irradiation damage effects have gained prominence.Up to now,the studies on irradiation damage effects of InGaAs IR-PDs have mostly focused on the degradation of dark current,irradiation damage mechanism,and evaluation and anticipation of irradiation damage.In this paper,spatially resolved and temperature-dependent PL spectra are performed to investigate the influence on microstructure and in-plane uniformity of an InGaAs/InP p-i-n focal plane array（FPA）PD induced by gamma irradiation.The elucidation of the irradiation damage mechanism can promote further applications of InGaAs devices in radiation environments.The major contents are summarized as follows:（1）Based on the gamma-irradiation displacement damage model,we had calculated and evaluated the displacement of lattice atoms in the InGaAs device.As pointed out in the damage model,gamma irradiation first generates secondary electrons through ionization effect,and then the secondary electrons collide with the lattice atoms,which displace the lattice atoms and then modify the microstructure of the device.Atomic displacement theory calculations show that 20 krad（Si）and 100krad（Si）gamma irradiation produces a displaced atomic density of about 10¹² cm^-3,which are much smaller than the atomic density of InGaAs(～3.92×10²² cm^-3).This indicates that gamma irradiation has little effect on the host atoms and lattice structure of InGaAs devices.During gamma irradiation,the point defects generated by irradiation may interact with the original defects or impurities in the material,and defect annihilation,defect migration,or formation of defect complexes may occur.Therefore,the change in InGaAs device performance induced by gamma irradiation mainly originates from the change in defect structure.（2）The in-plane uniformity of unirradiated,20 krad（Si）and 100 krad（Si）gamma-irradiated InGaAs IR-PD had been characterized using room-temperature（T=290 K）and low-temperature（T=3 K）spatially resolved PL spectra.The room-temperature PL results show that the effect of gamma irradiation on the room-temperature PL spectra and its in-plane uniformity is small,which indicates the strong anti-radiation stability of the InGaAs devices operating at room temperature.The low-temperature PL results show that gamma irradiation reduces the acceptor-related luminescence significantly,indicating gamma irradiation damage the impurity/defect structures.The in-plane uniformity of the low-temperature PL spectra changes very little after irradiation,indicating that the effect of gamma irradiation on the impurity/defect structures is uniform.（3）The microscopic damage mechanism of gamma irradiation had been elucidated by comparing the temperature-dependent PL spectra and combining with the calculation results of atomic displacement.Gamma irradiation microscopic damage process:Gamma rays passing through InGaAs devices ionize the atoms and generate secondary electrons,which collide elastically with lattice atoms and introduce point defects in the lattice.The point defects generated by irradiation interact with the original defects in the material and undergo defect migration,defect elimination or defect complex formation.Point defects tend to move to the interface and form defect complexes,affecting the occupation of carriers near the interface;point defects can also combine with charged impurity atoms,turning some impurities into inactive defect-impurity complexes.The elucidation of the gamma irradiation damage process deepens the understanding of the interaction between irradiation and devices and is of great significance for the work on radiation hardening of devices.