Electronic Transport and Depletion of Quantum Wells by Tunneling through Deep Levels in Semiconductor Superlattices

We have observed a series of narrow peaks in the low-temperature photocurrent-voltage characteristic of multiple-quantum-well $p-i-n$ junctions grown by molecular-beam epitaxy. In addition, the forward dark current and capacitance exhibit a steplike decrease at the same voltages of the photocurrent peaks. These features provide the first direct evidence of electronic transport as well as of depletion of quantum wells by tunneling through deep levels in the barrier layers in semiconductor superlattices.