STUDIES OF THE ASYMMETRY OF PHONON EMISSION FROM HOT CARRIERS IN THE QUANTUM HALL REGIME OF GAAS

We have made measurements of the phonon intensity emitted by hot carri ers in the entry and exit corners of two-dimensional electron and hole gases (2DEGs and 2DHGS) in single GaAs/(AlGa)As heterojunctions in th e quantum Hall regime (QHR). The intensity was measured normal to the 2DG. In 2DEGS, for the whole power range studied, the normal intensity from the electron exit corner is appreciably lower and we attribute t his to a change in angular distribution due to hot-electron transmissi on into the 3D contact. The difference in behaviour from Si is attribu ted to the difference in relaxation rate associated with the effective masses. Dissipation from the entry and exit corners has also been see n for the first time in a magnetically quantized 2DHG.