High-responsivity GaInAs/InP quantum well infrared photodetectors grown by low-pressure metalorganic chemical vapor deposition

We have studied the dependence of the well doping density in n-type GaInAs/InP quantum well infrared photodetectors (QWIPs) grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Three identical GaInAs/InP QWIP structures were grown with well sheet carrier densities of 1 x 10(11) cm(-2), 3 x 10(11) cm(-2), and 10 x 10(11) cm(-2); all three samples had very sharp spectral responses at lambda = 9.0 mu m. We find that there is a large sensitivity of responsivity, dark current, noise current and detectivity with the well doping density. Measurements revealed that the lowest-doped sample had an extremely low responsivity relative to the doping concentration while the highest-doped sample had an excessively high dark current relative to doping. The middle-doped sample yielded the optimal results. This QWIP had a responsivity of 33.2 A/W and operated with a detectivity of 3.5 x 10(10) cmHz(1/2)W(-1) at a bias of 0.75 V and temperature of 80 K. This responsivity is the highest value reported for any QWIP in the lambda = 8-9 mu m range. Analysis is also presented explaining the dependence of the measured QWIP parameters to well doping density.