Low-temperature electron mobility studied by cyclotron resonance in ultrapure GaAs crystals

Abstract

We report on a systematic study of the electron scattering processes in ultrapure GaAs crystals over the temperature range 1.6--100 K by using the classical cyclotron resonance (CR) for a low density of photogenerated electrons (${\mathit{n}}_{\mathit{e}}$\ensuremath{\sim}${10}^{10}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$). The highest electron mobility extracted from the CR data is 2.2\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ${\mathrm{cm}}^{2}$/V sec at T=1.6 K. The electron scattering due to the acoustic-phonon piezoelectric potential is found to be the main intrinsic electron-phonon scattering mechanism in the temperature range 1.6T30 K. Electron scattering by neutral impurities is shown to be significant even in these ultrapure GaAs crystals (unlike Ge and Si). The acoustic-phonon piezoelectric and deformation-potential coefficients as well as the impurity concentrations (\ensuremath{\sim}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) were obtained from the analysis of the electron-scattering-rate dependence on temperature. A CR line narrowing is observed under increasing microwave power and is interpreted as due to a decrease in the acoustic-phonon piezoelectric scattering efficiency with electron heating. The electron effective mass determined from the CR magnetic field applied along [001] is ${\mathit{m}}^{\mathrm{*}}$=(0.0662\ifmmode\pm\else\textpm\fi{}0.0002)${\mathit{m}}_{0}$.