Abstract
We have compared the phonon emission from the hot two-dimensional electron gas (2DEG) confined in molecular beam epitaxy (MBE) grown quantum wells (QWs) of width 50 and 100Åusing the heat pulse technique. At low powers in the acoustic phonon regime the 50ÅQW sample showed a relatively larger proportion of emission into longitudinal acoustic (LA) mode phonons than the 100Åwell sample. We suggest this results from momentum conservation restrictions associated with the different 2DEG widths of the two samples. At the highest powers ( ∼ 100pW per electron) well into the optic phonon regime, both samples show the onset of a new path for acoustic emission that cannot be accounted for by electronic transitions to extended states in the bulk. We note that the effect occurs for the same classical drift velocity (μE) in the two samples.
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