Observation of a negative differential resistance due to tunneling through a single barrier into a quantum well

Abstract
We have observed a negative differential resistance (NDR) in a single-barrier tunneling structure in which electrons tunnel from a doped semiconductor emitter layer into a quantum well (QW) layer and subsequently drift laterally to a specially designed contact. Pronounced NDR is seen already at room temperature and at 77 K the peak to valley (PTV) ratio in current is more than 2:1. Our results lend support to a recent hypothesis by Luryi [Appl. Phys. Lett. 47, 490 (1985)] that the NDR in double-barrier tunneling structures is not related to a resonant enhancement of the tunneling probability at selected electron energies, but rather originates from tunneling into a system of electron states of reduced dimensionality. For comparison we have also fabricated a QW structure with two tunneling barriers, in which the parameters of the emitter barrier and the QW are identical to those in the single-barrier structure. In the double-barrier structure we have obtained current densities as high as 4×104 A/cm2 and a NDR with PTV ratios of 3:1 at 300 K and 9:1 at 77 K.