Thermalization length of hot electron-LO-phonon subsystem in heavy-doped n-GaAs

The heat transport in heavy-doped n-GaAs has been investigated at temperatures T = 300 K and 77 K using the irradiation of the metal-semiconductor contact by modulated CO2-laser radiation. It is shown that this approach gives an opportunity to determine the thermo-diffusion coefficient chi and Seebeck coefficient S-T without direct measurements of the temperature gradient. It was also found that the ratio of the characteristic heated-zone scale to the excited heat wavelength exceeds by an order of magnitude the assessment that can be obtained from the reference data for GaAs. To elucidate the origin of the observed phenomenon the measurements were conducted with Schottky contacts made on the thin-doped GaAs layer epitaxially grown on the semi-insulating GaAs substrate. In this case, the degenerate electron gas occupies only an insignificant part of the heat-conducting medium. In addition, the injection of hot electrons into the semiconductor by current pulses through the Schottky barrier was used to clear up whether there is a dependence of the effect on the method of electron heating. The nonequilibrium of LO-phonons and the change in the electron-phonon collisional integral due to the nonequilibrium pair correlations of the electrons are suggested as a possible explanation.