Resonant tunneling in aluminum gallium arsenide/gallium arsenide double-barrier structures

Double-barrier resonant tunneling structures are exciting tools for investigating the fundamental physics of quantum transport, and potentially interesting building blocks for novel semiconductor devices. In this thesis, we present the study of double-barrier resonant tunneling heterostructures consisting of a GaAs quantum well between two Al{dollar}sb{lcub}x{rcub}{dollar}Ga{dollar}sb{lcub}1-x{rcub}{dollar}As barrier layers. First, we report the experimental observations on the area and temperature dependence of the hysteresis in the current-voltage characteristics of double-barrier resonant tunneling diodes. Our observation shows that the hysteresis can result from a load line effect. We further compare the data with theoretical predictions from the intrinsic bistability picture, and obtain the criterion for observing current bistability. Secondly, the incoherent tunneling mechanisms in double-barrier resonant tunneling diodes are investigated by using the magnetotunneling techniques. The inter-Landau-level and LO phonon-assisted resonant tunneling with high index are well resolved in our devices. We further report the observation of two-dimensional resonant magnetopolarons in double-barrier structures. The polaron-induced pinning, splitting, and specific sample-related features are observed in the current-voltage characteristics. The LO phonon-assisted spin flip-flop resonant tunneling is observed at the first time. We also conclude that the magneto-oscillations in the current-magnetic-field curves at constant biases are not related to the electron density in the accumulation layer. Finally, we apply the concept of double-barrier resonant tunneling structure to a three-terminal device. We report the observation of step-like drain current and negative transconductance in the double-quantum-well field-effect resonant tunneling transistor. The competition between the vertical and horizontal transport processes also leads to the first observation of an idealized, delta-function-like current-voltage characteristics in resonant tunneling devices. The time-dependent transport mechanisms in this transistor will also be discussed.