Electron temperature of hot spots in quantum Hall conductors

Spectroscopic studies are carried out on the cyclotron emission from the hot spots of GaAs∕AlGaAs two-dimensional electron gas systems in a quantum Hall regime at B=6.00.3em0exT (ν=2.5) and 7.50.3em0exT (ν=2.0) at T=4.20.3em0exK by applying a terahertz scanning microscope. The spectra at the current entry and exit corners (hot spots) are remarkably broadened towards lower frequencies with increasing I up to 3000.3em0exμA, indicating the significant relevance of higher excited Landau levels. The spectra are analyzed by assuming that the effective electron temperature, TE, at the local injection/withdrawal point reaches a maximum ~3000.3em0exK while it is TE=25--300.3em0exK when averaged over the region determined by the spatial resolution (500.3em0exμm diameter).