극성/무극성 6H-SiC 쇼트키 베리어 다이오드 제조 및 전기적 특성 연구

Abstract

We have fabricated schottky barrier diode (SBDs) using polar (c-plane) and non polar (a-, m-plane) n-type 6H-SiC wafers. Ni/SiC ohmic contact was accomplished on the backside of the SiC wafers by thermal evaporation and annealed for 20minutes at <TEX>$950^{\circ}C$</TEX> in mixture gas (<TEX>$N_2$</TEX> 90% + <TEX>$H_2$</TEX> balanced). The specific contact resistance was <TEX>$3.6{\times}10^{-4}{\Omega}cm^2$</TEX> after annealing at <TEX>$950^{\circ}C$</TEX>. The XRD results of the alloyed contact layer show that formation of <TEX>$NiSi_2$</TEX> layer might be responsible for the ohmic contact. The active rectifying electrode was formed by the same thermal evaporation of Ni thin film on topside of the SiC wafers and annealed for 5 minutes at <TEX>$500^{\circ}C$</TEX> in mixture gas (<TEX>$N_2$</TEX> 90% + <TEX>$H_2$</TEX> balanced). The electrical properties of SBDs have been characterized by means of I-V and C-V curves. The forward voltage drop is about 0.95 V, 0.8 V and 0.8 V for c-, a- and m-plane SiC SBDs respectively. The ideality factor (<TEX>${\eta}$</TEX>) of all SBDs have been calculated from log(I)-V plot. The values of ideality factor were 1.46, 1.46 and 1.61 for c-, a- and m-plane SiC SBDs, respectively. The schottky barrier height (SBH) of all SBDs have been calculated from C-V curve. The values of SBH were 1.37 eV, 1.09 eV and 1.02 eV for c-, a- and m-plane SiC SBDs, respectively.