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 the oretically, An analytical model of the QWIP is developed. The model ta kes into account the main processes responsible for the QWIP operation , namely, the electron tunneling from the emitter, capture of the elec trons into the QW, their photoexcitation from the QW, and electron dri ft or ballistic transport across the QWIP structure. Analytical expres sions for the QWIP responsivity as functions of the modulation frequen cy of infrared radiation, its power density, and the QWIP structural p arameters are obtained from the rigorous self-consistent small-signal analysis. It is shown that there are two distinct ranges where the fre quency dispersion of the responsivity is strong. At low frequencies, t he responsivity dispersion is associated with the inertia of the proce ss of recharging of the QW while at very high frequencies the dispersi on is due to the electron transit-time effect, The influence of the el ectron transit-time effect on the QWTP admittance is also evaluated, T he derivation of the QWIP high-frequency performance and, in particula r, the estimates of 3-dB bandwidth show that the QWIP's have a great p otential for devices utilizing both infrared radiation and millimeter or submillimeter wavelength microwave signals.