A new approach to investigate leakage current mechanisms in infrared photodiodes from illuminated current-voltage characteristics

Abstract

This paper presents a new approach to investigate leakage current mechanisms in infrared photodiodes from the illuminated current–voltage characteristics. The example of mid-wave mercury cadmium telluride photodiodes is presented to illustrate the new approach. The new method is suitable for evaluating diodes in an array environment as advance knowledge of any of the material or device parameters are not required. The thermal saturation current is estimated from the observed open circuit voltage and zero-bias current (photo-current) of the diode. The ohmic shunt resistance is estimated from the observed maximum dynamic impedance of the diode. The experimentally observed reverse bias diode current in excess of thermal current, photo-current, and ohmic shunt current is reported to be best described by an exponential function of the type, Iexcess = Ir0 + K1 exp (K2 V), where Ir0, K1, and K2 are fitting parameters and V is the applied bias voltage. Our investigations reveal a close link between the excess current and the sources of ohmic currents in the diode. Exponential growth of excess current with the applied bias voltage has been interpreted as an indication of soft breakdown of the diodes.