Transition behaviors in biased asymmetric quantum dot-in-double-well photodetector

• An asymmetric quantum-dot in double well (DdWELL) structure is newly designed.
• The triple-band mid-/far-infrared (MIR/FIR) photodetector is tunable by polarity.
• MIR/FIR PR bands are blue/red-shifted by the bias voltage.
• MIR–FIR dual-band spectrum is changed to single-band by the polarity.
• A four-level energy band diagram is proposed for the origin of the PR transitions.

A triple-band mid-/far-infrared (MIR/FIR) photodetector tunable by polarity is demonstrated by asymmetric quantum dot-in-double-well (DdWELL) structure that exhibits unique photoresponse (PR) transitions. In contrast to the MIR2 band with no dependence, the two MIR1/FIR PR bands are blue/red-shifted by the bias voltage, and the MIR2-FIR dual-band spectrum changes to a single-band feature due to the polarity. A four-level energy band model is proposed for the transition scheme, and the electric field dependence of the FIR band numerically calculated by a simplified DdWELL structure is in good agreement with the experimental PR spectra.