The design and demonstration of microwave band silicon carbide static induction transistors for power applications
Abstract
The static induction transistor (SIT) allows extremely high power densities well into the S-band. This is due to the vertical current flow and close packing of multiple channels controlled by a single input to the Schottky gates. By constructing the SIT from silicon carbide (SiC) the blocking voltage can be increased well above that of silicon or gallium arsenide while reducing the on-state resistance. In addition, SiC's high thermal conductivity allows heat to be effectively removed from the SIT structure increasing reliability. The goal of the work presented in this document is to increase the frequency response of the SIT by aggressively scaling down critical dimensions, which adversely affect frequency response. At the same time, doping levels are kept low enough that the breakdown voltage should remain high. Detailed explanations of each processing step are given along with recommendations for improving future devices. Devices have been fabricated demonstrating a short-circuit unity current gain frequency, ft, of 8.65 GHz and a maximum frequency of oscillation, fmax, of 5.66 GHz. Devices exhibit power gains of over 11 dB at 3.5 GHz. Large area devices exhibit maximum power outputs in class A operation of 3.2 W with a power density of 42 kW/cm2. Small area devices (0.54 W total output power) increase the power density to 102 kW/cm2.
Degree
Ph.D.
Advisors
Melloch, Purdue University.
Subject Area
Electrical engineering
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