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 <0001> 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 <0001> 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 (V_D) to breakdown voltage (V_B) compared with those for <$11\bar{2}0$> direction 4H-SiC IMPATT diode, which lead to higher-millimeter-wave power output for <0001> 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 <0001> 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 <0001> direction 4H-SiC IMPATT diode.