Photoemission of Si   1 s → 2 p z transition in GaAs/AlGaAs quantum wellfor zero-dimensional states infrared detection

Intersubband absorption in a GaAs/AlGaAs quantum well usually happens between two two-dimensional (2D) electronic states. However for sufficiently low doping levels, the electrons can be entirely distributed on the silicon localized states. We demonstrate that depending on the temperature, absorption in such structures is dominated either by 2D quantum well states or by zero-dimensional localized Si states. We find a regime where the localized states are the main contributors to the photocurrent, this is expected to strongly impact the behavior of quantum well infrared photodetectors.