<title>Advances in the processing of quantum-coupled devices</title>

Abstract

It has recently been demonstrated[1,2] that zero-dimensional semiconductor structures (quantum dots) can be fabricated with electrical contact to individual dots, and that the current voltage characteristics correspond to tunneling through the discrete density of states of a zero-dimensional system[3]. Because the density of states in such a quantum dot is a series of delta functions there is the potential for sharp transitions between tunneling and non-tunneling (on and off) states in devices fabricated from quantum dots. Such devices therefore could form the basis of a post-VLSI integrated circuit technology. These quantum dot devices are laterally-confined variations on the resonant tunneling diode (RTD). RTDs consist of a two dimensional quantum well surrounded by tunnel barriers. RTDs exhibit current peaks when electron energies in their contacts are aligned with quantum states in the well. As the quantum well states drop below the emitter conduction band edge, the current falls and there is negative differential resistance (NDR). Quantum dot diodes (QDDs) are RTDs which have lateral dimensions small enough to split the sub-bands in the quantum well into discrete energy states. This lateral confinement also creates 1-d sub-bands in the contact regions adjacent to the dot which become one dimensional quantum wires, leading to a more complex situation than exists in large area RTDs.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.