Double-barrier resonant tunneling in three and two dimensions

Double-barrier resonant tunneling devices have attracted great scientific interest, both as novel physical systems based on strong size quantization that exhibit unusual transport behavior and also as a promising class of semiconductor structures for high-speed electronic devices. This thesis describes the physics of transport in double-barrier structures fabricated by conventional planar growth, where the fundamental process involves tunneling from three-dimensional (3D) into two-dimensional (2D) densities of electronic states, as well as in novel 2D double-barrier structures fabricated by regrowth, where 2D electrons tunnel into well-separated ID quantum wire subbands. A brief introduction to the basic theory of resonant tunneling and the results of low-temperature I(V) transport measurements on high-quality planar double-barrier devices is presented in Chapter 1. Chapter 2 examines the bistable I(V) characteristic observed in specially designed asymmetric devices, with the intrinsic nature of this effect confirmed by parallel field magnetotunneling measurements. In Chapter 3 transverse field magnetotunneling is employed to experimentally verify the energy and transverse momentum selection rules that govern transport in resonant tunneling devices. Chapter 4 focuses on the fabrication of 2D resonant tunneling devices by liquid phase epitaxial regrowth on patterned substrates. A brief overview of liquid phase epitaxy and two different in-situ patterning techniques--selective meltback and cleaving inside the chamber--are presented. The measurements of the 2D device fabricated by regrowth on cleaved substrates are presented and analyzed in Chapter 5. The new possibilities opened up by the cleaved substrate regrowth techniques are also discussed, including the realization of an edge-regrown superlattice with novel high-field transport characteristics.