Energy relaxation by hot electrons in n-GaN epilayers

The energy relaxation rate for hot electrons in n-type GaN epilayers has be en measured over the temperature range 1.5-300 K. Several samples grown by molecular-beam epitaxy and having different electron concentrations have be en studied. At low electron temperatures (T-e< 20 K), the energy relaxation is via acoustic phonon emission. The magnitude and temperature dependence of the energy relaxation are found to be in good agreement with theoretical calculations using appropriate values of the deformation potential and pie zoelectric coupling constants and ignoring screening. For T(e)greater than or equal to 70 K, the dominant mechanism of energy loss is optic phonon emi ssion. For the several samples studied, consistent values of the optic phon on energy and electron-optic phonon relaxation time, 90 +/-4 meV and 5-10 f s, respectively, are measured. The energy agrees well with values obtained by other methods and the relaxation time is consistent with theoretical cal culations of the Frohlich interaction and indicate that hot phonon effects are absent up to 10(-8) W/electron dissipation. (C) 2001 American Institute of Physics.