Investigation of p-type strained-layer InxGa1-xAs/AlyGa1-yAs quantum well infrared photodetectors for long wavelength infrared imaging arrays applications

Two p-type compressively strained-layer (PCSL) InxGa1-xAs/AlyGa1-yAs (where, x = 0.4, 0.2; y = 0, 0.15) quantum well infrared photodetectors (QWIPs) grown by MBE on (100) semiinsulating (SI) GaAs substrates have been investigated for 3-5 mu m MWIR and 8-14 mu m LWIR imaging arrays applications. The In0.4Ga0.6As/GaAs PCSL-QWIP utilizing the resonant transport mechanism between the heavy-hole type-I states and the light-hole type-II states shows a broadband double-peak response between 8 and 9 mu m range. Using compressive-strain in the InGaAs quantum well, normal incident absorption was greatly enhanced by reducing the heavy-hole effective mass and increasing the density of states in the off-zone center. Maximum responsivities of 93 mA W-1 and 30 mA W-1 were obtained at peak wavelengths of lambda(p1) = 8.9 mu m and lambda(p3) = 5.5 mu m, respectively at V-b = 1.6 V. and detectivity (D*) at lambda(p1) = 8.9 mu m was found to be 4.0 x 10(9) cm-root Hz/W at V-b = 0.3 V and T = 75 K for this QWIP. The In0.2Ga0.8As/Al0.15Ga0.85As PCSL-QWIP achieves two-color detection with peak wavelengths at 7.4 mu m in the LWIR band and 5.5 mu m in the MWIR band. This detector is under background limited performance (BLIP) at T = 63 K for biases varying from -2.7 V to + 3 V. A detectivity (D*) of 1.06 x 10(10) cm root Hz/W was obtained at lambda(p) = 7.4 mu m, V-b = 1.0 V and T = 81 K for this QWIP. (C) 1996 Academic Press Limited