High-frequency performance of single quantum well infrared photodetectors at high power densities

The high-frequency properties of quantum well infrared photodetectors (QWIP's) based on a double-barrier single QW structure are studied theoretically. An analytical model of the QWIP is developed. The model takes into account the main processes responsible for the QWIP operation, namely, the electron tunneling from the emitter, capture of the electrons into the QW, their photoexcitation from the QW, and electron drift or ballistic transport across the QWIP structure. Analytical expressions for the QWIP responsivity as functions of the modulation frequency of infrared radiation, its power density, and the QWIP structural parameters are obtained from the rigorous self-consistent small-signal analysis. It is shown that there are two distinct ranges where the frequency dispersion of the responsivity is strong. At low frequencies, the responsivity dispersion is associated with the inertia of the process of recharging of the QW while at very high frequencies the dispersion is due to the electron transit-time effect. The influence of the electron transit-time effect on the QWIP admittance is also evaluated. The derivation of the QWIP high-frequency performance and, in particular, the estimates of 3-dB bandwidth show that the QWIP's have a great potential for devices utilizing both infrared radiation and millimeter or submillimeter wavelength microwave signals.