INTERSUBBAND PHOTOCURRENT FROM THE QUANTUM-WELL OF AN ASYMMETRICAL DOUBLE-BARRIER STRUCTURE

A detailed study of intersubband photocurrents from the single quantum well of an asymmetrical double-barrier resonant tunneling structure is reported. Measured current-voltage characteristics are compared with a self-consistent calculation. The calculation also gives the density of electrons accumulated in the quantum well, and the lower and the upper resonant state escape times. Photocurrents from the quantum well are induced by 9 and 10.6-mu-m photons using a CO2 laser, which are directly proportional to the electron densities in the well. The observed photocurrents are much larger in the bias polarity where the thicker barrier is on the collector side consistent with theory. Our experiments show directly that a substantial accumulation of electrons occurs even for undoped quantum wells.