Performance evaluation of high-power wide band-gap semiconductor rectifiers

Applicability of GaN in unipolar and bipolar devices for high-power electronic applications is evaluated with respect to similar devices based on other materials. Specific resistance is used as a measure of unipolar performance. In order to evaluate bipolar performance, 700 and 6000 V p-i-n diodes based on Si, 6H-SiC, and GaN are compared with respect to forward conduction and reverse recovery performance at room temperature and high-temperature conditions. It is shown that GaN is advantageous not only for high voltage unipolar applications, but also for bipolar applications. An empirical closed-form expression is presented to predict the avalanche breakdown voltage of wide band-gap semiconductors. Formulation of the expression is based on an approximation of the impact ionization coefficient in terms of seventh power of the electric field.