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 (sigma) were obtained as 1.03 eV and 0.117 V from the slope and intercept of this plot, respectively. Thus, the modified ln(Io/T-2) - q(2)sigma o(2)/2k(2)T(2) versus q/kT plot gives mean BH and the modified Richardson constant 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.