Influence of the anisotropy on the performance of D-band SiC IMPATT diodes

Abstract

Numerical simulation has been made to predict the RF performance of direction and < $$ 11\bar{2}0 $$ > direction p+/n/n−/n+ (single drift region) 4H silicon carbide (4H-SiC) impact-ionization-avalanche-transit-time (IMPATT) diodes for operation at D-band frequencies. We observed that the output performance of 4H-SiC IMPATT diode is sensitive to the crystal direction of the one-dimensional current flow. The simulation results show that direction 4H-SiC IMPATT diode provides larger breakdown voltage for its lower electron and hole ionization rates and higher dc-to-rf conversion efficiency (η) for its higher ratio of drift zone voltage drop (VD) to breakdown voltage (VB) compared with those for < $$ 11\bar{2}0 $$ > direction 4H-SiC IMPATT diode, which lead to higher-millimeter-wave power output for direction 4H-SiC IMPATT compared to < $$ 11\bar{2}0 $$ > direction. However, the quality factor Q for the < $$ 11\bar{2}0 $$ > direction 4H-SiC IMPATT diode is lower than that of direction, which implies that the < $$ 11\bar{2}0 $$ > direction 4H-SiC IMPATT diode exhibits better stability and higher growth rate of microwave oscillation compared with direction 4H-SiC IMPATT diode.