On the analysis of space-charge-limited current—voltage characteristics and the density of states in amorphous silicon

Abstract

An expression is derived for the current-voltage characteristic under space-charge-limited conditions when the density of deep states increases exponentially with energy above the Fermi level. This shows that the slope of a logJ - log V curve increases slowly and only reaches the limiting value of (l + 1) (where l = T _c/T and T _c characterizes the steepness of the exponential) at voltages above those used in practical experiments. This invalidates the procedure of deriving values for T _c by fitting straight lines to experimental log J - log V plots and suggests an explanation of some anomalous results published recently.

Some brief comments are made on the values of T _c to be expected for a-Si: H.