Molecular beam epitaxy of strain-compensated InGaAs/GaAsP quantum-well intersubband photodetectors

We report on the growth of quantum well intersubband photodetectors (QWIPs) with InGaAs wells grown on GaAs. Arsenic species and substrate temperature were varied to investigate their effects on the photoluminescence (PL) and lattice relaxation of 40 period InGaAs/GaAs QWIP samples. Both PL intensity and lattice relaxation decreased with decreasing substrate temperature - the PL dropping steeply below 500 degrees C and the relaxation dropping gradually below 470 degrees C. In all cases examined, however, the relaxation was at least 33% as measured by asymmetric (115) five crystal X-ray scans. Introducing a small percentage of phosphorous into the barriers to partially strain-compensate the structure was found to dramatically reduce the lattice relaxation while maintaining the highest PL intensity. Comparison of this strain-compensated InGaAs/GaAsP QWIP with the optimized InGaAs/GaAs QWIP revealed that the dark current was reduced by a factor of 4 while the photocurrent remained virtually unchanged resulting in an increase in the background limited operating temperature by approximately 3 K.