Wide bandgap semiconductor design, processing, and characterization

Wide bandgap semiconductors have shown promising results in high power, high frequency, and high temperature application. There is also huge interest in the development of MOSFET due to lower power consumption, larger voltage swing, and better stability. Since the minority carrier generation rate of gallium nitride (GaN) is extremely slow, it is very difficult to achieve the inversion under the gate using conventional way. Unlike Silicon, GaN does not have high quality native oxide, instead novel oxides such as magnesium oxide (MgO) and scandium oxide (Sc2O3) were employed as the gate oxides for GaN based MOSFET. This dissertation contains the first demonstration of inversion using both MgO and Sc2O3 as the gate oxides. Gate-controlled diodes were successfully fabricated to supply minority carriers to under the gate region by implanting Si ions around gate area.; Most applications in wide bandgap semiconductors are required to be operated in a harsh environment, therefore, the degradation of metal contacts is critical for long term stability of the devices. Tungsten (W) and tungsten silicide (WSi) based refractory metallizations were deposited on both GaN and SiC using sputter technique for the applications of high temperature operations. However, damage was introduced to the semiconductor due to ion bombardment during the sputtering and post-sputtering high temperature annealing is required to remove the ion bombardment damage. The optimum condition of the thermal annealing was found by measuring current-voltage to achieve low diode turn-on resistance and highest barrier height. A study of the effect for gamma-irradiation on the stability of different metallizations was conducted. W and WSi based metallization contacts displayed superior stability as compared to nickel (Ni) contacts under irradiation condition.; Since wide bandgap semiconductors can stand high temperature, they can be fabricated into sensors that operate at elevated temperatures such as engines and reactors. Hydrogen sensors using both platinum (Pt) and palladium (Pd) as Schottky contacts have been demonstrated. With introduction of hydrogen gas to the GaN Schottky diodes, the barrier height of catalytic Schottky contacts was changed. The change of the Schottky barrier height was fully reversible.