Dual-color charge-sensitive infrared phototransistors with dynamic optical gate

Infrared multispectral photodetectors with high performance show great potential in a broad range of applications. Here, sensitive and controllable dual-color photodetection at 10.6 and 15.7 μm is demonstrated by using a charge sensitive infrared phototransistor (CSIP) with dynamical optical gate. The CSIP device is fabricated in a GaAs/AlGaAs double quantum well (QW) crystal with both upper and lower QWs (7 and 11 nm thick, respectively) being photosensitive via intersubband absorption and, hence, each QW corresponding to one target wavelength ( 10.6 and 15.7 μm, respectively). Moreover, the upper QW serves as a photosensitive floating gate (FG), while the lower QW functions as the conducting channel of the phototransistor. By periodically lifting-up (lowering-down) the electrostatic potential of FG, the photoresponse at 10.6 ( 15.7 μm) associated with photoexcitation in upper (lower) QW can be achieved. This electrically controllable photoresponse together with intrinsically high photoconductive gain (∼102) provides a scheme to realize sensitive dual-color photodetection for infrared optoelectronic applications.