Energy relaxation by hot carriers in wurtzite GaN epilayers

In this paper, we report hot carrier energy relaxation processes studied by acoustic phonon emission in wurtzite GaN epilayers, using the heat pulse technique. In this method, the carriers were heated up by means of short (≈ 10 ns) voltage pulses and emitted phonons were detected by Al bolometers biased at their superconducting transition. Obtained phonon signals indicate that the optical phonon emission threshold has not been reached and longitudinal acoustic and transverse acoustic modes can be clearly resolved. This paper specifically concentrates on the electron temperature dependence of the energy relaxation rates and compares the experimental results with the existing theory.