Current conduction mechanism in Al/p-Si Schottky barrier diodes with native insulator layer at low temperatures

Abstract

The forward bias current–voltage ( I– V) characteristics of Al/p-Si (MS) Schottky diodes with native insulator layer were measured in the temperature range of 80–300 K. The obtained zero bias barrier height Φ B0( I– V), ideality factor ( n) and series resistance ( R s) determined by using thermionic emission (TE) mechanism show strong temperature dependence. There is a linear correlation between the Φ B0( I– V) and n because of the inhomogeneties in the barrier heights (BHs). Calculated values from temperature dependent I– V data reveal an unusual behaviour such that the Φ B0 decreases, as the n and R s values are increasing with decreasing absolute temperature, and these changes are more pronounced especially at low temperatures. Such temperature dependence of BH is contradictory with the reported negative temperature coefficient of the barrier height. In order to explain this behaviour we have reported a modification in the expression reverse saturation current I o including the n and the tunnelling factor ( αΧ 1/2 δ) estimated to be 15.5. Therefore, corrected effective barrier height Φ bef.( I– V) versus temperature has a negative temperature coefficients ( α = −2.66 × 10 −4 eV/K) and it is in good agreement with negative temperature coefficients ( α = −4.73 × 10 −4 eV/K) of Si band gap. In addition, the temperature dependent energy distribution of interface states density N ss profiles was obtained from the forward bias I– V measurements by taking into account the bias dependence of the Φ e and n. The forward bias I– V characteristics confirm that the distribution of N ss, R s and interfacial insulator layer are important parameters that the current conduction mechanism of MS Schottky diodes.