Abstract
We present a study of electric instability in GaAs/AlGaAs hetero-structure two-dimensional electron gas system under high magnetic fields. As the applied dc current exceeds a threshold value Ith, the longitudinal voltage Vxx drops, fluctuates and exhibits electric instability. The observed instability occurs only in well-separated low-lying Landau levels with a filling factor ν ≦ 2 at relatively high lattice temperatures. We find that Ith increases with increasing magnetic field B and the lattice temperature TL. In contrast, electric instability becomes more pronounced at higher B, but gradually diminishes with increasing TL. The onset of electric instability has been predicted by two phenomenological theories, one is the theory of Andreev et al. [25], and the other is the theory of Kurosawa et al. [ 1]. Data analysis suggests that longitudinal resistance Rxx is suppressed by increasing I and exhibits negative differential resistivity (NDR) when I = Ith, where NDR is viewed as a precursor signal of electric instability. The electric instability is caused by domain growth. The electric instability is actuated by the suppression of Rxx with increasing I, which can be understood in terms of the capability of the spectral diffusion of electrons and electron transfer to higher levels via inelastic inter-Landau levels scattering within the limit of one-occupied Landau level.