Influence of Surface Structure on Electrical Characteristics in SiC MESFETs

摘要

SiC MESEETs have been developed for advantageous use in high power microwave devices due to unique material properties, such as, high saturated electron velocity, high breakdown field, and high thermal conductivity. In this work, the influence of surface structure on SiC MESFETs has been studied by investigating electrical characteristics, such as DC, small signal, and large signal characteristics. Three different structures have been fabricated and compared with each other: channel-recessed, gate-recessed, and buried-gate structures. Fig. 1 shows cross-sections of each type. The epitaxial structure consisted of a lightly doped 0.25μm p-type buffer layer and a 0.26μrn n-type channel layer doped 2×10{sup}17 cm{sup}(-3) without a heavily doped n-type layer on the top. The footprint of the T-shaped gates was 0.40 - 0.45μm, and the recessed regions were etched 60 nm deep. All the devices were passivated using a PECVD Si{sub}3N{sub}4 film.