Design and simulation of semiconductor device

Abstract

Abstract

This thesis describes the application of Monte Carlo modelling to the simulation of Gunn diode devices while focusing on devices composed of Gallium Arsenide (GaAs). It also describes systematic work on the design and characterization of planar Gunn diodes and the better design of the contacts to enhance RF output power and novel contact designs to produce high frequencies.

Initially, we investigated the cause of the irregular heating within the channel of the diodes which produced weakened Gunn domains near the edges of the channel. It was observed that Gunn domains are attracted to these corners, resulting in a perturbation in the formation of the domains, which leads to chaotic dynamics within the rest of the channel and consequently to irregular heating and reduced RF output power. However, by blunting the contact corners, the resulting current is considerably more orderly with defined peaks sharper and improved than the sharp corner contacts design.

Additionally, improved device design has proven to be one of the key methods of increasing higher RF power and frequency. With a new planar Gunn diode design with shaped anode and cathode contacts, it is possible to have devices that operate both with and without feedback potential (in delayed mode) that have shown fine structure frequency components of 350 GHz in a device with a nominal transit time frequency of 70 GHz.

Finally, this research aimed to find ways to improve the performance of planar Gunn diodes using a detailed simulation analysis of the device design, giving the potential for very high frequency power generation and other wave shaping applications.