On the anomalous peak and negative capacitance in the capacitance–voltage (C–V) plots of Al/(%7 Zn-PVA)/p-Si (MPS) structure

The frequency and voltage dependence of the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics of the Al/(%7 Zn-doped PVA)/p-Si (MPS) structure were investigated in the wide range of frequency and voltage. Frequency and voltage dependence of C and G/ω shows that these parameters are functions of frequency and voltage. The C–V plot has an anomalous peak and an intersection/crossing point around 1.4 V after which C becomes negative. This negative capacitance (NC) phenomena was attributed to the surface states (N_ss), series resistance (R_s) and minority carrier injection. The intensity of NC decreases with increasing frequency and the minimum value of C corresponds to the maximum value of G/ω at strong accumulation region. Whereas the C–V plots have only one peak at low frequencies, they have two peaks at high frequencies due to the special density distribution of N_ss and their relaxation time. In addition, the changes in the C and G/ω were attributed to the increase in the polarization and the increased number of carriers in the structure. Impedance method was used for calculation of R_s whereas N_ss was obtained using two methods; (i) the high–low frequency capacitance and (ii) Hill-Coleman method as a function of voltage and frequency, respectively. The Fermi energy level (E_F), the concentration of doping acceptor atoms (N_A) and barrier height (Φ_B) values were obtained from reverse bias C⁻² vs V plots for each frequency.