Local breakdown of the quantum hall effect and the correlated cyclotron emission

Spatial distribution of the cyclotron radiation emitted from nonequilibrium electrons is studied on 1.5 mm-wide Hall bars in the quantized Hall effect (QHE) regime. At low current levels where the two terminal resistance is quantized, the location of the cyclotron emission (CE) is restricted to the electron entry and exit corners formed between the metallic current contacts and the two-dimensional electron gas (2DEG) layer. As current increases, additional CE occurs in the vicinity of the corner of the source contact that is opposite to the electron entry corner. The additional CE is accompanied by a finite voltage drop. The experimental results demonstrate that in sufficiently wide Hall bars the QHE breaks down locally in the vicinity of the source contact before the breakdown develops in the entire 2DEG channel.