Simulation of gallium nitride Gunn diodes at various doping levels and temperatures for frequencies up to 300 GHz by Monte Carlo simulation, and incorporating the effects of thermal heating

Abstract

The performance and operation of GaN Gunn diodes has been investigated for a number of device structures and at various temperatures using a three-valley Monte Carlo model incorporating the heat diffusion equation. Simulated structures include both notched and uniform transit regions, with the performance of each also observed at fixed temperatures from 350 to 500 K. Finally, the long-term function of an ideal GaN Gunn diode was simulated to observe the effect of temperature increases as a result of operation, and to estimate the time it would take the device to cool sufficiently to allow unlimited cycles of pulsed operation. It was found that in order to obtain ∼300 GHz operation, the optimum device structure required a notched transit region. Significantly, it was also found that the longer term effect of heat on the device performance, with respect to the device frequency over each cycle, was considerable, a result which raises fundamental questions as to the viability of such devices.