Device applications of double barrier resonant tunneling structures.

Abstract

The purpose of this work is to determine the potential and capability of double barrier resonant tunneling diodes as useful high frequency electronic devices. The diode was modeled using a quantum transport formalism in order to understand various device properties. It was found that diode properties such as the peak current density, peak-to-valley current ratio, and device capacitance can all be controlled by the proper device design. A current peak-to-valley ratio of 6(21) at 300 K (77 K) for a lattice matched InGaAs/InAlAs device and 24(51) at 300 K (77 K) for a pseudomorphic InGaAs/AlAs device were measured. These are some of the highest peak-to-valley ratios measured in the respective material systems. The devices were fabricated in a manner to facilitate whisker contacts and to remove the substrate in order to reduce the device parasitic resistance. The measured dc I(V) characteristics display various anomalies and it is shown experimentally that three commonly observed instabilities are due to diode switching, diode bistability, and bias circuit oscillations. The effect of various circuit parameters on the instabilities are discussed and demonstrated experimentally. The potential and capability of the diode as a microwave power source was investigated using small and large-signal analyses. The effect of stability on the power generation capability of the diodes was studied showing the importance of the lead inductance. It is argued that stability requirements will seriously reduce the output power from these devices for conventional lead inductances. The diodes have been experimentally characterized as video detectors in the frequency range of 10-100 GHz. Such detector properties as the tangential signal sensitivity, dynamic range, and open circuit voltage sensitivity have been measured for the first time and it is demonstrated that the performance of the diode in various aspects is comparable to existing device technologies. The noise properties of the diode were studied with the help of a self-oscillating mixer experiment. The measured minimum detectable signal was poor relative to other existing devices.