Asymmetry of the Breakdown near Hot Spots in the Quantum Hall Regime in a Specially Shaped GaAs/AlGaAs Sample

Behavior of the electron injection (extraction) position into (from) a two-dimensional electron gas (2DEG) at the interface with electrode was specified in the breakdown of the quantum Hall effect (QHE) by measuring the threeterminal resistance of a specially shaped GaAs/AlGaAs heterojunction sample. In the quantum Hall regime, the current injection from the electrode into the 2DEG (or current extraction out of the 2DEG) occurred at a point on the corner of the 2DEG referred to as a hot spot. When the current was increased to cause the breakdown of QHE at the same magnetic field, a shift of the current-injection/extraction position was observed only on the source-side electrode where electrons were injected into the 2DEG. This asymmetry indicates that breakdown only occurs near the hot spot on the source side. The mechanism of this asymmetry was fairly quantitatively explained on the basis of bootstrap-type electron heating near the hot spot by taking the distribution of electric field there into consideration.