We have measured the energy relaxation rate of hot electrons in MBE grown bulk GaN epilayers on GaAs and sapphire substrates over the electron temperature range 1 - 130 K. The measurements were made using heat pulse techniques. For layers grown on GaAs substrates the results show that the carriers reside in the substrate, probably as in a GaAs/AlGaAs heterojunction. For layers grown on sapphire substrates we obtain a P \propto T^4_e dependence for the relaxation rate in the low temperature limit, consistent with piezoelectric coupling in the so-called `dirty' regime, changing to a linear dependence in the high temperature, equipartition, regime.
HAWKER, P.; KENT, A. J.; CHENG, T. S.; and FOXON, C. T. (1999) "Energy Relaxation Rate of Hot Electrons in N-Type GaN Epilayers using Heat Pulse Techniques," Turkish Journal of Physics: Vol. 23: No. 4, Article 11. Available at: https://journals.tubitak.gov.tr/physics/vol23/iss4/11