Terahertz operation of quantum-well intersubband hot-electron phototransistors

A novel infrared photodetector utilizing intersubband electron transitions and plasma wave excitation in a quantum well (QW)-the QW intersubband hot-e lectron phototransistor (MEPT)-is proposed and evaluated. It is shown that the excitation of standing plasma waves in the QW base by incident modulate d infrared radiation can result in resonant response of IHEPT's. The plasma resonance peaks of the linear responsivity of IHEPT's with a base contact spacing of about 1 mu m correspond to the terahertz range of modulation (si gnal) frequencies. The resonant peaks of the responsivity can be tuned by t he biasing voltage. The peak value of the IHEPT resonant responsivity can b e of the order of the steady-state responsivity of standard QW intersubband infrared photodetectors, significantly exceeding the high-frequency perfor mance of the latter. Relatively large values of the IHEPT resonant responsi vity are associated with strong injected current stimulated by the plasma w aves in the QW-base. Finally, it is shown that the nonlinear dependence of the injected current on the potential of the QW base results in the variati on of the de current with changing signal amplitude. The nonlinear response current as a function of the modulation frequency also exhibits resonant b ehavior with the peaks at the plasma resonance frequencies and can be used for the detection of the signal component envelope.