Electron-phonon coupling of a two-dimensional electron gas in a Si metal-oxide-semiconductor field-effect transistor in the temperature range $0.3\mathrm{K}<T<\mathrm{}4\mathrm{}\mathrm{K}$ has been investigated using phonon-drag thermopower $S^g$ and electron energy loss rate $F\left(T\right).$ At low temperatures (the Bloch limit) we find $S^g\propto T^6,$ as expected for electron-phonon scattering mediated by a screened deformation potential, and the magnitude is in excellent agreement with a calculation using no adjustable parameters; the calculation continues to give good agreement at higher temperatures. $F\left(T\right)\mathrm{}$ has been calculated using the same input parameters as for $S^g.$ Reasonably good agreement is found with the observed values for $T>\mathrm{}1.5\mathrm{}\mathrm{K},$ but at lower temperatures the measured $F\left(T\right)\mathrm{}$ is much larger than predicted and also exhibits a much weaker temperature dependence. Possible reasons are suggested.

• Received 7 July 1997

DOI:https://doi.org/10.1103/PhysRevB.56.12422