Discrepancies in barrier heights obtained from current-voltage (IV) and capacitance-voltage (CV) of Au/PNoMPhPPy/n-GaAs structures in wide range of temperature

Au/n-GaAs device was fabricated with an organic PNoMPhPPy thin polymer interfacial layer whose bandgap (E-g) was found as 2.95 eV from the (alpha hv)(2)-hv plot. The PNoMPhPPy poly(N-substituted pyrrole) was characterized by SEM. The evaluation of positive bias I-V-T results revealed an-abnormal decreases of ideality-factor (n) and increases of barrier-height (BH) with increasing of temperature. For instance, the values of BH [Phi(b(IV))] for the Au/PNoMPhPPy/n-GaAs were found as 0.84 eV (at 400 K), 0.82 eV (300 K) and 0.23 eV (at 60 K) from the ln(I)-V plots with a positive temperature coefficient (1.79 meV/K), whereas, Phi(b(CV)) was found as 1.27 eV and 1.64 eV at 400 and 60 K from the C-2-V plots with a negative temperature coefficient (- 0.44 meV/K), thus exhibits similar behavior compared with the bandgap of GaAs (alpha = Delta E-g/Delta T = - 0.473 meV/K). These findings together with the inconsistency between Phi(b(IV)) and Phi(b(CV)) is the result of barrier-inhomogeneity and such temperature-dependence of Phi(b(IV)) and n was explained on the basis of TE-theory with "Double-Gaussian-Distribution" (DGD) of BHs. Additionally, the observed some discrepancies in the electrical parameters extracted from the forward bias IV and reverse bias CV was attributed to the nature of measurement system and voltage dependent of them.