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. (C) 2008 American Institute of Physics.