Multiquantum-well detection of nanosecond far-infrared superradiant pulses at temperatures above 77 K

A lightly doped GaAs/(Ga,Al)As multiquantum-well sample is shown to be a fast detector of 2-5-ns wide far-infrared (FIR) pulses in the wavelength range from 100 to 500 microns. The conditions for optimum bias, sign of the photosignal, and non-linearity in the low-temperature current-voltage curve suggest that the detection mechanism is hot-electron photoconductivity. The responsivity is optimum near liquid-helium temperature where the detector response time is 2 ns. Furthermore, we observe for the first time in quantum wells, long-wavelength IR detection at temperatures above 77 K with a superradiant pulse-width-limited response time of less than 1 ns. (Author)