Resonant Tunneling in InGaAs-InP Double-Barrier Structures and Superlattices.

We have studied the perpendicular transport in the double- barrier structures of the InGaAs-InP system, with particular focus on reducing the large leakage current caused by conduction at the perimeter of the device. Results obtained on a sample which had low doping in the electrode layers, such that the Fermi level of the emitter electrode was below the first subband level at low bias, are presented. These results demonstrate unambiguously that the process of selectively etching the device has been successful in suppressing the leakage current. A peak- to-valley ratio of 4.3 was obtained for this sample at 4.2K. We have also carried out the first investigation of the perpendicular transport in InGaAs-InP superlattice structures. These structures exhibit a large series of periodic negative differential resistances whose number and period are controlled by the number of the width of the quantum wells respectively.