Single Gaussian distribution of barrier height in Al/PS–ZnPc/p-Si type Schottky barrier diode in temperature range of 120–320 K

Abstract

Possible current-transport mechanism in aluminum/polystrene–zincphthalocyanine/ptype silicon Schotky barrier diode (Al/PS–ZnPc/p-Si; SBD), for the forward bias current–voltage (I–V) characteristics were carried out in the temperature range of 120–320 K. The high value of ideality factor (n), especially at low temperatures, was attributed to the existence of PS layer, barrier in-homogeneities and particular density distribution of surface states between metal and semiconductor. An abnormal decrease in the zero-bias barrier height (BH) and increase in n with decreasing temperature which leads to non-linearity in the Richardson plot, have been observed. Linear relationship between BH and n was also observed. BH was plotted as a function of q/2kT to obtain evidence of Gaussian distribution (GD) of the BHs. The mean BH and its standard deviation (σ) were obtained as 1.03 eV and 0.117 V from the slope and intercept of this plot, respectively. Thus, the modified ln(Io/T²) − q²σo²/2k²T² versus q/kT plot gives mean BH and the modified Richardson constant ${\text{A}}_{\bmod }^{*}$ as 1.043 eV and 29.824 A cm⁻² K⁻², respectively. This value of the Richardson constant is very close to the theoretical value of 32 A cm⁻² K⁻² for p-type Si. Therefore, non-ideal behavior of forward-bias I–V characteristics in Al/PS–ZnPc/p-Si might be successfully explained in terms of the thermionic emission mechanism with single GD of BHs.