Strained p-type InGaAs/AlGaAs multiple quantum well infrared photodetectors

Strained p-type In0.15Ga0.85As/Al0.33Ga0.67As quantum well infrared photodetectors (QWIPs) with different Be concentrations in their wells, which detect normal infrared incidence, were investigated. The QWTPs with a Be doping density of 10(18) cm(-3) in the wells show a cut-off wavelength of 7.9 gm and basically symmetric detectives of about 8 x 10(8) cm.Hz(1/2)/W at 600 Hz. By increasing the Be doping density in the wells to 2 x 10(19) cm(-3), the cut-off wavelength is blue-shifted to about 7.25 meV and the photoreponsivity and detectivity become asymmetric. The detectivity is increased to about 1.4 x 10(9) cm.Hz(1/2)/W at positive biases but significantly reduced at negative biases. The blue shift in the cut-off wavelength for the QWIP devices with heavy doping concentration in the wells is mainly due to the bandgap shrinkage and the increased well width while the asymmetric behaviour in the photoresponsivity and detectivity is likely due to the inhomogenity resulting from dopant diffusion at high doping.