The effects of reduced dimensionality and elastic scattering on the current voltage characteristics of resonant tunneling diodes

Two terminal devices with negative differential conductance effects (NDC) have been used for several decades in a variety of electronic applications. The existing diode technologies which give such effects have a limited number of adjustable parameters, and constraints on frequency of operation which have limited their application. The development of molecular beam epitaxy (MBE) has enabled the developement of a new class of quantum devices including the resonant tunneling diode (RTD). The RTD has shown the potential to operate from D.C. into the THz frequency range. The range of adjustable parameters available give the RTD great flexibility in design, but also increase the complexity of understanding transport through the device.; The current-voltage (I-V) characteristics of an RTD are modeled within the assumption of coherent electron wavefunctions through the structure and a separation of variables condition. These assumptions are broken by the presence of ionized impurities within the device, yet such impurities are essential to device design. In order to determine the effect of such impurities on the I-V characteristics, a set of RTD's was fabricated with different types of impurities in the center of the device. A shift in the peak current of the device is correctly predicted by the I-V model, however, a degradation of the ratio of the peak current density to the valley current density (peak to valley ratio), is not correctly predicted by the model. A scattering assisted tunneling mechanism is proposed to account for the discrepancy.; Advanced lithographic techniques have created the capability to introduce additional quantum confinement transverse to the direction of current flow. The effects of this additional confinement in a resonant tunneling device are studied theoretically. First the problem is solved assuming that the variables can be separated in the direction along and the direction transverse to the current flow. It is found that under these conditions that no additional peaks are manifested in the current-voltage characteristics of these devices. The violation of the separation of variables condition is introduced as a perturbation to the previous system. It is found that a perturbation due to an elastic scattering center can cause additional structure in the current-voltage characteristics of such devices.