MOLECULAR-BEAM EPITAXY OF STRAIN-COMPENSATED INGAAS GAASP QUANTUM-WELL INTERSUBBAND PHOTODETECTORS/

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