Turkish Journal of Physics




In recent years photodetectors operating in the mid- to far infrared region of 3-15 \mu m have been designed based on electron and hole intersubband transitions in multiple quantum wells and superlattices. In general, QWIPs based on electron transitions show greater detectivity compared to the hole-based photodetectors. However, selection rules for electron intersubband transitions usually forbid the TE mode operation, associated with normal light incidence; Therefore, special coupling structures/geometries have been employed to couple light into the device. The spectral region 3-5 \mu m is of interest for a variety of applications such as environmental gas sensing, thermal imaging etc. and is not well covered by existing detectors. We have grown a QWIP operating at \sim 3\mu m with a normal incidence component which incorporates an InGaAs/GaAs asymmetric quantum well from which photo-excited carriers undergo resonant tunnelling into the AlGaAs barriers. A study of temperature-dependent dark current of this device is presented with a view to obtaining enhanced detectivity at high temperatures.

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