Trap-assisted tunneling current and quantum efficiency loss in InGaAsSb short wavelength infrared photo detectors

Abstract

Abstract We report the trap-assisted tunneling current and quantum efficiency (QE) loss in short wavelength infrared In0.22Ga0.78As0.2Sb0.8 photo detectors. Combining experiment data with a current–voltage model, we found that the trap-assisted tunneling current was boosted by increasing Beryllium (Be) doping in active region at room temperature. However higher Be doping level imposes no negative impacts on QE. Four traps with energy levels located at 49 meV , 60 meV , 155 meV and 199 meV below conduction band minimum in a In0.22Ga0.78As0.2Sb0.8 alloy are extracted from the fitting of I–V curves. Transparency measurement of an un-intentional doped In0.22Ga0.78As0.2Sb0.8 sample yields an absorption coefficient of 5191 cm−1 at 2.25   μ m . Combining with the measured value of absorption coefficient, the QE dependence on diode length of In0.22Ga0.78As0.2Sb0.8 photo detectors is presented. Finally, by fitting quantum efficiencies of In0.22Ga0.78As0.2Sb0.8 photo detectors, we obtained that the minority electrons diffusion length is larger than 4   μ m and the minority holes diffusion length is 0.2   μ m . QE loss occurs at top N region of In0.22Ga0.78As0.2Sb0.8 photo detectors due to a short holes diffusion length.