Energy density distribution profiles of surface states, relaxation time and capture cross-section in Au/n-type 4H-SiC SBDs by using admittance spectroscopy method

Abstract

Au /n-type 4H - SiC diodes were fabricated and their electrical characteristics have been investigated by using the capacitance/conductance-voltage-frequency (C–V–f and G/w–V–f) measurements method at room temperature. The main parameters such as the doping atoms (ND), diffusion potential (VD) and barrier height (ΦB(C–V)) values were obtained from the reverse bias C-2–V plots for each frequency. C and G/ω values decrease with increasing frequency as almost exponential for each voltage and these changes in C and G/ω are considerably high at low frequencies due to the contribution of surface states (Nss) to the measured C and G/ω. The resistivity (Ri) versus V plots were also obtained by using the C and G data and they exhibit an anomalous peak which is corresponding to the depletion region at each frequencies and its magnitude decreases with increasing frequency. The energy density distribution of Nss and their relaxation time (τ) were obtained from the conductance method and they range from 1.53 × 1014 eV-1 cm-2 to 1.03 × 1014 eV-1 cm-2 and 1.29 × 10-4 s to 3.35 × 10-5 s, respectively, in the energy range of (0.585-Ev) – (0.899-Ev) eV. The voltage dependent of Nss was also obtained from C HF – C LF method. The obtained value of Nss is about 1014 eV-1 cm-2 order and these values are suitable for an electronic device.