HEATING OF 2-DIMENSIONAL ELECTRONS BY A HIGH-ELECTRIC-FIELD IN A QUANTIZING MAGNETIC-FIELD - CONSEQUENCES IN LANDAU EMISSION AND IN THE QUANTUM HALL-EFFECT

We study the electric-field-induced heating process of a two-dimension al electron gas in the quantum-Hall-effect (QHE) regime. We present bo th theoretical and experimental results. We calculate the inter-landau -level transition probabilities under high electric field, in the pres ence of both phonon and impurity scattering. We deduce from the theore tical investigations the total emitted power of the cyclo-tron emissio n as a function of the electric-field intensity. We perform both cyclo tron emission and quantum transport experiments, on GaxAl1-xAs/GaAs an d GaxIn1-xAs/GaAs heterojunctions, at liquid-helium temperature and ma gnetic fields up to 8 T, using samples with different geometry. We the refore distinguish several cyclotron emission regimes and we demonstra te, with theoretical arguments, that the average electric field in the sample is not a good physical parameter in the description of the hea ting process and of the cyclotron emission for a two-dimensional elect ron gas. We finally present experimental results which tend to prove t hat the local electric held can be high enough in some parts of the sa mple, to induce inter-Landau-level scattering, and consequently to gen erate the cyclotron emission and to induce the breakdown of the quantu m Hall effect. The role of the microscopic local electric field is con firmed by the observation of the emitted power amplification in the pl ateaus regime of the QHE. This phenomenon is due to the modification o f the current path geometry and the enhancement of the local electric field in the vicinity of the contact point in the QHE regime.