Direct measurements of energy relaxation time of electrons in AlGaAs/GaAs heterostructures under quasi-equilibrium conditions

For the first lime, results are presented of a direct measurement of the energy relaxation time tau(epsilon) of 2D electrons in an AlGaAs/GaAs heterojunction at T=1 and 5-20 K. A weak temperature dependence of tau(epsilon) for the T>4 K range and a linear temperature dependence of the reciprocal of tau(epsilon) for T<4K have been observed. The linear dependence tau(epsilon)(-1)approximate to T in the Bloch-Gruneisen regime is direct evidence of the predominance of the piezo-electric mechanism of electron-phonon interaction in non-elastic electron scattering processes. The values of tau(epsilon) in this regime are in very good agreement with the results of the Karpus theory. At higher temperatures, where the deformation-potential scattering becomes noticeable, a substantial disagreement between the experimental data and the theoretical results is observed.