Barrier breakdown in multiple quantum well structure

We explore a regime of unipolar electronic transport in a multiple quantum well structure with very large current discontinuities-up to five orders of magnitude. Magnetotransport experiments reveal different transport regimes. Quantum well impact ionization shifts the structure from a resistive "down" state, where the current flows through interwell quantum tunneling, to a highly conductive "up" state. In the latter regime, the current leaks through a barrier suddenly broken down because of an efficient ionization of the first quantum well. This mechanism might open the way to original devices based on unipolar impact ionization.