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

Abstract

The frequency and voltage dependence of the capacitance-voltage (C-V) and conductance-voltage (G/omega-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/omega 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/omega 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/omega 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 (I broken vertical bar(B)) values were obtained from reverse bias C-2 vs V plots for each frequency.