Study On The Irradiation Characteristics Of Short Wavelength Infrared InGaAs Detector

In Ga As material covers the short wave infrared atmospheric window of 1-3μm. The particular spectroscopic features enable In Ga As detectors to be widely applied in aerospace remote sensing. The abundant high energy particle irradiation in the aerospace can degenerate the performance of photodectectors and even break the photodectectors. Focusing on the application of In Ga As detectors in aerospace remote sensing, the irradiation effects of the detectors were studied to provide reference for guaranteeing the reliable operation in the aerospace. The materials applicable for μPCD measurement were grown to extract the minority carrier lifetime of lattice-matched In0.53Ga0.47 As and this investigation laid a foundation for characterizing the effect of irradiation on the minority carrier lifetime. The 1/f noise characteristics of In0.83Ga0.17 As photodiodes passivated by ICPCVD and PECVD were compared; the dependence of g-r noise on temperature was used for extracting the defect level; these works have made preparations for characterizing the irradiation effect by low-frequency noise. The γ ray irradiation experiments including ex-situ and in-situ measurements were performed for In0.53Ga0.47 As and In0.83Ga0.17 As detectors; the effects of irradiation on the performances of detectors were observed; the dark current mechanisms before and after irradiation were analyzed. The degenerations of the performances of In0.83Ga0.17 As materials and detectors from proton irradiation were investigated; the variations of low-frequency noise components caused by irradiation were discussed.Extracting the minority carrier lifetime of In0.53Ga0.47 As material by μPCD measurement was explored. According to the experiment results of various materials with different structures and parameters, it is concluded that the magnitude of measurement signal were influenced remarkably by the conductance of material and the distance from sample to metal platform. In order to obtain effective signal, it is better to grow epitaxy material on semi-insulating substrate and control the conductance to be less than 40 m S. The nin type In0.52Al0.48As/In0.53Ga0.47 As double heterostructures epitaxy material was grown and measured. Effective signal was observed. In the case that the In0.52Al0.48 As layers provide good surface passivation, the effective lifetime extracted from the signal decay curve is the minority carrier lifetime of In0.53Ga0.47 As material.The low-frequency noise of In0.83Ga0.17 As detectors was studied. First, the 1/f noise characteristics of photodiodes passivated by PECVD and ICPCVD were investigated. Compared with PECVD passivation, ICPCVD passivation improves the surface quality and suppresses the 1/f noise significantly. The 1/f noise of the diodes passivated by PECVD has an exponential relationship with reverse bias, whereas for the diodes passivated by ICPCVD, the relationship satisfies a power law. With the temperature declining, the 1/f noise of the diodes passivated by ICPCVD decreases more rapidly than that of the diodes passivated by PECVD. It shows that the advantage of ICPCVD passivation becomes more conspicuous at the lower temperature. The origin of 1/f noise is investigated with variable area diodes. The observed geometry dependence indicates that the 1/f noise of the diodes passivated by PECVD dominantly comes from the perimeter and that of the diodes passivated by ICPCVD dominantly comes from the bulk and upper surface. Besides, the defect levels ET in the diodes with different areas passivated by PECVD were extracted by the dependence of g-r noise on temperature. They are ET=EC-0.28 e V in In Ga As layer and ET=EV+0.39 e V, 0.59 e V in In Al As layer.The ex-situ and in-situ tests γ ray irradiation experiments have been performed on In0.53Ga0.47 As detectors. In the ex-situ test experiment, the dark current increased obviously after 100 krad and 300 krad irradiation. The increased current components are mainly the diffusion and shunt component. The dark currents decreased by about 40% at the 22 h after irradiation. Then the dark currents remained stable until 240 h after irradiation. According to the temperature dependence of dark current, it is deduced that the increase of shunt current ?Ish∝exp(-0.43 e V/k T).The irradiation nearly has no impact on the response spectral of the detectors and the effective carrier density obtained by C-V curve for In Ga As layer. In the in-situ test experiment, the results indicate that the photocurrent induced by irradiation is about 2n A. Besides, the irradiation brings about cumulative damage which increases the dark current. No annealing of dark current was observed by about 10 minutes after irradiation. With the accumulation of irradiation dose under certain dose rate, the increase of dark current slows down. Under the same dose, the larger the irradiation rate is, the more the dark current increases. The In0.83Ga0.17 As detectors were irradiated by 480 krad γ ray, the results of ex-situ test suggested that the dark current and response spectral of detectors were next to unchanged after irradiation.The irradiation effects of 2Me V proton with fluences of 2×1013cm-2, 1×1014cm-2, 5×1014cm-2 and 1×1015cm-2 on the performance of In0.83Ga0.17 As detectors and materials have been investigated. The dark currents, low-frequency noise, detectivity and quantum efficiencies of the detectors, the PL spectral peak intensities of In Al As and In Ga As layers in materials all degenerate significantly after irradiation. However, the level of the degenerations does not increase monotonously with the increasing irradiation influence. It might be due to that the irradiation not only induces the defects by displacement effect, but also reduces the defects by “radiation-induced order effect”. The dark currents and low-frequency noise both recovered to a less extent after irradiation. The current densities are both next to independent on P/A before and after irradiation. It indicates that the irradiation mainly results in bulk damage. With the temperature declining, the dark currents after irradiation decrease more quickly than that before irradiation. It causes that the degeneration of dark current becomes more notably at the lower temperature. The analysis of low-frequency noise mechanisms shows that 1/f noise, g-r noise and white noise all increase after irradiation. The degeneration degree of quantum efficiency gradually rises with the wavelength increasing to be around the absorption edge of In Al As layer and then is alomost unchanged. It is likely because the decrease of PL intensity of In Ga As layer is much greater than that of In Al As layer, which is observed in the PL spectral measurement.