Structure and simulation of GaAs TUNNETT and MITATT devices for frequencies above 100 GHz

A numerical simulation program for two-terminal transit-time devices based on the energy-momentum transport model, with valence band to conduction band tunneling phenomena incorporated, has been developed. This program can deliver accurate TUNNETT and MITATT device simulation results in the millimeter and submillimeter range, and therefore provides a useful tool for high frequency device structure design and optimization. Simulation results for GaAs TUNNETT and MITATT devices for frequencies above 100 GHz are presented. As simulation results show, the negative resistance of the device decreases rapidly as the operating frequency increases. Under such circumstances, the contact resistance severely degrades the device´s RF performance. When a diode´s negative resistance becomes lower than the contact resistance, no RF power can be generated. To overcome this difficulty, device structures using no ohmic contacts are investigated. In these devices, ohmic contacts are replaced by Schottky contacts, and also p-n junctions are replaced by Schottky junctions for single-drift structures. Since the metal-semiconductor contact resistance is eliminated or greatly reduced in such devices, they are very promising as RF power sources at extremely high frequencies