Measurement of intersubband absorption in multiquantum well structures with monolithically integrated photodetectors

Abstract

Intersubband absorption in GaAs/AlGaAs multiple quantum wells (MQW) is measured using a novel integrated detector-waveguide structure. The responsivity spectra of MQW infrared photodetectors is demonstrated to follow exactly the intersubband absorption spectra at various temperatures and bias. The blue shift of the bound-to-continuum state intersubband absorption peak with lowering of temperature is observed to track the change of the conduction-band offset. The absorption peak showed only a slight Stark shift since the field in the wells is small in these narrow-well/thick-barrier structures and partly screened by the high doping.