Comparative study of the temperature-dependent dielectric properties of Au/PPy/n-Si (MPS)-type Schottky barrier diodes

Abstract

The dielectric properties of Au/PPy/n-Si metal-polymer-semiconductor (MPS)-type Schottky barrier diodes (SBDs) were investigated by using capacitance-voltage (C-V) and conductancevoltage (G/ω-V) measurements at various temperatures and voltages at frequencies of 100 kHz and 500 kHz. Both the real and the imaginary parts of the complex dielectric constant and dielectric loss (e′, e″) and of the electric modulus (M′, M″), as well as the conductivity (σac), were found to depend strongly on the temperature and the voltage. Both the C and G/ω values increased with increasing applied voltage and had inversion, depletion, and accumulation regions as with a metal-insulator-semiconductor (MIS) type behavior. Both the dielectric constant (e′) and the dielectric loss (e″) increased with increasing temperature and decreased with increasing frequency. The loss tangent (tan δ) vs. temperature curve had a peak at about 200 K for both frequencies. The M′ and the M″ values decreased with increasing temperature and became independent of the frequency at high temperatures. The series resistance (Rs) of the diode decreased with increasing temperature for the two frequencies while the σac increased. Such behaviors of the dielectric properties with temperature were attributed to the restructuring and reordering of charges at interface states/traps due to the varying temperature, the interfacial polarization, and the interfacial polymer layer. ln(σac) vs. q/kT plots had two distinct linear regions with different slopes for the two frequencies. Such behaviors of these plots confirmed the existence of two different conduction mechanisms corresponding to low and high temperatures. The values of the activation energy (Ea) were obtained from the slopes of these plots, and its value at low temperatures was considerably lower than that at high temperatures.