PHONON-ELECTRON INTERACTIONS IN THE 2-DIMENSIONAL ELECTRON-GAS IN INGAAS-INALAS MODULATION-DOPED FIELD-EFFECT TRANSISTOR STRUCTURES STUDIEDBY RAMAN-SCATTERING

Raman scattering by coupled longitudinal optic phonons and two-dimensi onal electron gas electrons in In0.53Ga0.47As-In0.52Al0.48As delta-dop ed heterostructures provides a powerful probe of electronic properties in these In-based structures. The two highest frequency modes, of the three coupled electron-phonon modes expected in this system, were obs erved, with the highest frequency mode being identified in InGaAs-base d systems. The large dispersion of this mode makes it a particularly s ensitive probe for changes in such properties as carrier concentration and subband energy. For structures with higher carrier concentrations coupling of the longitudinal optic phonon to multiple electron inters ubband transitions is resolved. These measurements are particularly us eful for heavily doped structures for which room-temperature Hall meas urements cannot distinguish channel electrons from those in parallel c onduction paths.