Effect of γ-ray irradiations on the performance of InGaAs infrared detectors was studied. Planar-type 24×1 linear detector arrays were fabricated on n-InP/n-In0.53Ga0.47As/n-InP epitaxial structure by sealed-ampoule diffusion method. The InGaAs detectors were irradiated by 100krad, 300krad γ-ray at 40rad/s. The dark currents increased about 170%, 300% respectively and both decreased about 23% at the 8th hours and about 40% at the 22th hour after irradiation. Then the dark currents almost remained stable until 10 days after irradiation. Current-Voltage characteristics of the planar-type detector were analyzed. The current mechanisms were dominated by diffusion current, shunts current and generation-recombination current before irradiation. The γ irradiation resulted to increase these three current components. Ten days after irradiation, three current components all recovered partially. Capacitance-Voltage characteristics were measured before and after irradiation. Effective doping densities (Neff) of InGaAs layer were deduced by fitting 1/C2-V curves. Neff of detectors which were irradiated by 100krad γ-ray increased after irradiation and remained the same until 10 days after irradiation. Neff of detectors which were irradiated by 300krad γ-ray unchanged after irradiation. The response spectrums both moved slightly towards shorter wavelength after irradiation and stayed the same until at least 10 days after irradiation.
The InGaAs focal plane array (FPA) detectors, covering the near-infrared 1~2.4 μm wavelength range, have been developed for application in space-based spectroscopy of the Earth atmosphere. This paper shows an all-metal vacuum package design for area array InGaAs detector of 1024×64 pixels, and its architecture will be given. Four-stage thermoelectric cooler (TEC) is used to cool down the FPA chip. To acquire high heat dissipation for TEC’s Joule-heat, tungsten copper (CuW80) and kovar (4J29) is used as motherboard and cavity material respectively which joined by brazing. The heat loss including conduction, convection and radiation is analyzed. Finite element model is established to analyze the temperature uniformity of the chip substrate which is made of aluminum nitride (AlN). The performance of The TEC with and without heat load in vacuum condition is tested. The results show that the heat load has little influence to current-voltage relationship of TEC. The temperature difference (ΔT) increases as the input current increases. A linear relationship exists between heat load and ΔT of the TEC. Theoretical analysis and calculation show that the heat loss of radiation and conduction is about 187 mW and 82 mW respectively. Considering the Joule-heat of readout circuit and the heat loss of radiation and conduction, the FPA for a 220 K operation at room temperature can be achieved. As the thickness of AlN chip substrate is thicker than 1 millimeter, the temperature difference can be less than 0.3 K.
The dark current characterization of InxGa1-xAs with x=0.78 have been investigated. Meanwhile, the dark current related deep level trap with Et= 0.26 eV is detected by using Deep-Level Transient Spectroscopy (DLTS). 2D simulation of dark current shows that SRH recombination, trap-assisted tunneling and band-to-band tunneling currents are the main contributors to the dark current of InxGa1-xAs( x=0.78) detector. To further improve the dark current characteristic, we need to improve the material growth.
Planar 64x64 In0.83Ga0.17As focal plane arrays (FPA) were fabricated in this paper. The properties of In0.83Ga0.17As photodetectors such as I-V, responsivity, detectivity were characterized. Theoretical analysis and measurement of the dark current behavior of the detectors at 200-300K were presented. The typical bad pixels caused by excessive dark current were analyzed, the result shows that they are mainly caused by more ohmic current and trap-assisted tunneling current component. Dark current density is 0.986μA/cm2 at an operating temperature of 200K and a bias voltage of -10 mV. The relative spectral response is in the range of 1.38 μm to 2.6 μm at 280K. The peak spectral response wavelength and quantum efficiency are 2.2 μm and 71.2% at 280K respectively. The achieved peak detectivity can reach 4.05x1011cmHz1/2W-1 by thermoelectric cooling at 200K.