Shunt current in InAs diffused photodiodes

The shunt current has been investigated in p+-n type InAs diffused photodiodes. The mesastructures were prepared by etching in Br2-HBr solution and sequentially etched in CP-4 and in a lactic acid based etchants. The surface of mesastructures was passivated in alcohol solution of Na2S. After each chemical treatment, the current-voltage and capacitance-voltage characteristics were measured as functions of bias voltage and temperature. It has been shown that the shunt current contains ohmic and non-ohmic components. The evidences have been obtained that the non-ohmic shunt current originates from the space-charge limited current in the surface inversion layer and the trap-assisted tunneling current in the bulk.