Simulation on different orientation hexagonal SiC-based hetero-polytype IMPATT terahertz diodes

Abstract

SiC hetero-polytypes that could be fabricated by chemical vapor deposition etc. methods can be employed to design the power devices. Herein, the 〈0 0 0 1〉(〈1 1 2¯ 0〉)4H(6H)-SiC-based hetero-polytypes are adopted to construct the n+/n/i/p/p+-type impact ionization avalanche transit time diodes (IMPATTDs) and mixed tunneling avalanche transit time diodes (MITATTDs). The DC, large-signal and noise performance of the proposed diodes operating at 0.85 THz are numerically simulated based on the fundamental equations for semiconductor devices. The results indicate that, the diodes with 〈0 0 0 1〉4H(6H)-SiC in each of the i-type, n-type and p-type regions can render higher break-down voltage and conversion efficiency while lower quality factor comparing to those with 〈1 1 2¯ 0〉4H(6H)-SiC in the three regions, the latter devices involve lower noise. The diodes contained 3C-SiC show lower break-down voltage and quality factor while higher noise than those without 3C-SiC. Little difference of DC, large-signal and noise properties between IMPATTDs and MITATTDs is implied due to very weak tunneling through thick intrinsic-region. The present diodes show higher conversion efficiency comparing to the n+/n/p/p+-type devices. In addition, the fabricating feasibility of the proposed devices is discussed. This paper can guide to design the reasonable structures by using suitable anisotropic semiconductors to achieve high-performance devices.