Hot electron energy relaxation via acoustic phonon emission in modulation-doped In0.53Ga0.47As/In0.52Al0.48As heterojunctions with double-subband occupancy

Abstract

The energy relaxation associated with acoustic phonon emission in lattice-matched ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}/{\mathrm{In}}_{0.52}{\mathrm{Al}}_{0.48}\mathrm{As}$ heterojunctions, has been investigated using Shubnikov-de Hass (SdH) effect measurements performed in the temperature range from 3.3 to 25 K, and at electric fields up to 200 ${\mathrm{Vm}}^{-1}.$ The thickness ${(t}_S)$ of the undoped spacer layer in modulation-doped samples was in the range between 0 and 400 Å. The SdH oscillations show that two subbands are populated for all samples except those with $t_S=400\mathrm{}$ Å. The electron temperature ${(T}_e)$ of hot electrons in each subband has been obtained from the lattice temperature ${(T}_L)$ and applied electric field dependencies of the amplitude of SdH oscillations. For the samples with $t_S=0,$ 100, and 200 Å, the power loss from the electrons in the first and second subbands is found to be proportional to ${(T}_e^3-T_L^3)$ for electron temperatures in the range $3.3<\mathrm{}{T}_e<12\mathrm{}$ K, indicating that piezoelectric scattering is the dominant scattering mechanism. For the samples with $t_S=400\mathrm{}$ Å, however, in which only the first subband is populated, the power loss is approximately proportional to ${(T}_e-T_L)$ in the same range of electron temperatures. The experimental results are also compared with a three-dimensional model for electron energy loss by piezoelectric and deformation-potential scattering.