InGaAsP/InP long wavelength quantum well infrared photodetectors

High quality InGaAsP/InP MQWs structures, grown by solid source molecular beam epitaxy, with different doping concentrations in the wells were investigated. High doping concentrations benefits absorption but is not good for dark current. The photocurrent spectra and peak values are sensitive to applied voltage. The total photocurrent comes from the electrons excited to two excited states. The decrease of the photocurrent peak value at high voltage can be explained by the reduction of photogenerated electrons. The detectivity of the InGaAsP/InP QWIP measured at a bias of − 2.5 V at 20 K is greater than 109cmHz/W, which is comparable to the GaAs/AlGaAs QWIPs.