TRANSPORT CHARACTERIZATION OF QUANTUM WIRES BY MAGNETOPHONON AND MAGNETIC DEPOPULATION EXPERIMENTS

We report magnetophonon resonance (MPR) studies on quantum wires fabri cated by the shallow etching technique. MPR are found to be strongly d ependent on the etching depth defining the lateral confinement. The su bband spacings extracted from MPR data, measured in the temperature ra nge between 100 K and 160 K turn out to be systematically higher than their values obtained from magnetic depopulation experiments. Simple m odel considerations allow an explanation of this effect. By tuning the electron density in the wires by means of a light emitting diode the carrier density dependence of subband spacings and polaron masses is i nvestigated by an analysis of the magnetophonon effect. Sublevel spaci ngs and polaron masses are found to increase when the electron density is reduced. The enhancement of sublevel spacing is clearly due to the reduction of screening of the bare confinement potential with decreas ing electron density. The behavior of the polaron mass as a function o f electron density presumably displays the influence of the confinemen t potential on the electron effective mass and is not yet clearly unde rstood. (C) 1997 Academic Press Limited.