Two-colour mid-infrared absorption in InAs/GaSb type II and broken-gap quantum wells under gated electric field

We present a detailed theoretical study on optical properties of an InAs/GaSb-based type II and broken-gap quantum well (QW) in the presence of gated electric voltage. Two absorption peaks were observed through intraband transitions within the same material layer. The intensity of optical absorption induced by inter-layer transition is relatively weak due to a small overlap of electron and hole wavefunctions at InAs/GaSb interface. The applied electric field can open up new channels for optical transition and thus affect significantly the optical absorption by changing the overlap of the electron and hole wavefunctions as well as the transition channels. The obtained results suggest that InAs/GaSb-based type II and broken-gap QWs can be employed as two-colour photodetectors working at mid-infrared bandwidth at relatively high temperatures. More over, the bandwidth of the optical absorption can be tuned by the gated electric field.