On the anomalous peak in the forward bias capacitance and conduction mechanism in the Au/n-4H SiC (MS) Schottky diodes (SDs) in the temperature range of 140–400 K

Abstract

The temperature and voltage dependence profile of the surface states (Nss), series resistance (Rs) and electrical conductivity (σ ac ) have been investigated in temperature and voltage ranges of 140–400 K and (-5 V )-(6 V ), respectively. The value of barrier height (BH) decreases with increasing temperature as ΦB(T) = (1.02 - 4×10-4⋅ T ) eV. These values of negative temperature coefficient (-4×10-4 eV ⋅ K -1) is in good agreement with the α of band gap of SiC (-3.1×10-4 eV ⋅ K -1). Capacitance-voltage (C–V) plots for all temperatures show an anomalous peak in the accumulation region because of the effect of series resistance (Rs) and Nss. The effect of Rs and Nss on the C and conductance (G) are found noticeable high especially at low temperatures. The decrease in C values also corresponds to an increase in G/ω values in the accumulation region. In addition, Ln (σ ac ) versus q/kT plots have two straight lines with different slopes which are corresponding to below and above room temperatures for various forward biases which are an evident two valid possible conduction mechanisms. The values of activation energy (Ea) were obtained from the slope of these plots and they changed from 6.3 meV to 4.7 meV below room temperatures and 42.5 meV to 34.4 meV for above room temperatures, respectively.