Spontaneous emission by ballistic electronics in semiconducting heterostructures : M. Botton and A. Ron. Solid-St. Commun.71(12), 1131 (1989)

Abstract

We have used nonequilibrium phonon-induced conductivity (phonoconductivity) measurements to probe the electronic states in semiconductor quantum wire devices. The devices were based on high mobility two-dimensional electron systems (2DESs) in GaAs/Al0.3Ga0.7As heterostructures and quantum wires formed using the well-known split-gate technique. Short (20 ns-long) pulses of nonequilibrium acoustic phonons were generated by heating a metal film on the back surface of the substrate. These phonons propagated ballistically across the substrate and were incident on the quantum wire. The electron–phonon interaction was detected via the phonon-induced change in electrical conductance of the device. We observed giant oscillations of the phonoconductivity with increasing (negative) gate bias. Maxima occurred when the Fermi energy was coincident with the bottom of any one-dimensional electronic subband. In this paper we argue that the phonoconductance is due to phonon-induced backscattering of the electrons in the quantum wire and present evidence that the strength of the phonon signal is proportional to the density of electronic states in the quantum wire.