Temperature and Field Dependence of Bound to Extended State Absorption in GaAs/AlGaAs Multiquantum Well Infrared Detectors.

Direct transmission measurements of long wavelength infrared (LWIR) absorption in n-doped GaAs/AlGaAs multi-quantum-well (MQW) structures are made at cryogenic temperatures and under applied bias. Comparison is made with detector responsivity spectra measured under the same conditions. The observed blue- shift of the intersubband absorption peak with lowering of temperature is in agreement with known temperature dependence of the band-edges. Only a slight Stark shift of the absorption peak is observed since the applied electric field is screened by the heavily doped wells. However, reversing the direction of the field gives an anomalous shift and broadening of the absorption spectrum.