SUPPRESSION OF DEFORMATION-POTENTIAL ELECTRON-ACOUSTIC-PHONON COUPLING IN SI DELTA-DOPED GAAS STRUCTURES

We have used the heat-pulse technique to investigate phonon emission f rom two-dimensional electron gases formed in a series of molecular-bea m-epitaxy- and metal-organic chemical-vapor-deposition-grown Si delta- doped GaAs structures with single subband occupation. By comparing the relative intensities of longitudinal and transverse acoustic-phonon e mission over a wide range of input powers (0.01-1000 pW per electron) we suggest that deformation-potential coupling to longitudinal modes i s suppressed in the acoustic regime (T-e<50 K). In all samples the ons et of optical-phonon emission was at input powers around 1.5 pW per el ectron, a value similar to that found in the heterojunction and quantu m-well cases. Strong LA-mode emission is observed at all powers in con trast to previous observations in the heterojunction system.