A two-stack, multi-color quantum well infrared photodetector for mid- and long-wavelength infrared detection

In this paper we report a high performance two-stack, multi-color quantum well infrared photodetector (QWIP) composed of an InGaAs/AlGaAs QWIP and an InGaAs/AlGaAs/InGaAs triple-coupled (TC-) QWIP grown on the GaAs substrate for mid- and long-wavelength (MW/LW) infrared (IR) detection. The basic device structure consists of a MWIR QWIP stack with 3 periods of a 43 Angstrom In0.3Ga0.7As quantum well and an undoped 300 Angstrom Al0.3Ga0.7As barrier and of a LWIR TC-QWIP stack with 5 periods of a 65 Angstrom In0.18Ga0.82As quantum well (QW) and two undoped 60 Angstrom In0.05Ga0.95As QWs separated by 20 Angstrom Al0.08Ga0.92As barriers. The TC-QWIP stack has two response peaks, which are voltage-tunable from 9.2 to 10 mum and 12 to 12.2 mum by the applied bias, respectively. For the LWIR TC-QWIP, a maximum responsivity of 1.96 A/W at 12 mum was obtained at T = 40 K, and a maximum detectivity of D* = 1.59 x 10(10) cm Hz(1/2)/W was estimated at V-b = -1.7 V, lambda(p) = 12 mum, and T = 20 K. As for the MWIR QWIP stack a responsivity value greater than 0.3 A/W at lambda(p) = 5.1 mum was obtained at 120 K, which was found to be nearly independent of the applied bias and temperature. (C) 2003 Elsevier Science B.V. All rights reserved.