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 t he energy relaxation time tau(epsilon) of 2D electrons in an AlGaAs/Ga As 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 o f the reciprocal of tau(epsilon) for T<4K have been observed. The line ar dependence tau(epsilon)(-1)approximate to T in the Bloch-Gruneisen regime is direct evidence of the predominance of the piezo-electric me chanism of electron-phonon interaction in non-elastic electron scatter ing processes. The values of tau(epsilon) in this regime are in very g ood agreement with the results of the Karpus theory. At higher tempera tures, where the deformation-potential scattering becomes noticeable, a substantial disagreement between the experimental data and the theor etical results is observed.