Photocurrent spectra of heavily doped terahertz quantum well photodetectors

Terahertz (THz) quantum well photodetectors (QWPs) are an important candidate for THz imaging and THz free space communication. Low absorption efficiency of THz QWPs is the main factor limiting the performance of this kind of THz detectors. To increase the absorption efficiency, three heavily doped THz QWPs were fabricated. The band structure calculations show that the second subband falls into the quantum well with increasing Si doping concentration, which decreases the escape probability of the photon-excited electrons in the second subband. This effect is responsible for the blueshift and broadening of the photocurrent peak with increasing Si doping.