Field-dependent mobility from space-charge-limited current-voltage curves

In the framework of one-carrier space-charge-limited currents, exact equations are derived for the evaluation of arbitrary field-dependent mobility. A differential method, which simply needs the first and second derivatives of measured current-voltage (I-V) curves, is presented for a trap-free case. Extension to a mixed case of exponentially distributed traps and field-dependent mobility is also outlined. In addition, a tool based on a combination of capacitance-voltage and I-V measurements was developed to certify the applicability of this method by checking whether the device tested is actually in the space-charge-limited regime. The extraction of the mobility from measurements can be a valuable tool for use in the theory: theoretical predictions of mobility field dependence can be easily compared to experimental results, thus permitting improvement of the models and fostering the development of transport theories. This method can also be of particular relevance for organic semiconductors whose field-dependent mobility has recently attracted so much theoretical and experimental work. (C) 2002 American Institute of Physics.