MIS diodes on n-InP having an improved interface

Metal-insulator-InP diodes with Al, Ni, Au and Pd Schottky contacts were fabricated using improved surface passivation techniques. The current-voltage (I-V) characteristics and the barrier height data indicate that a thin layer of thermal oxide between the metal-InP interface and a proximity cap protection during the RTA ohmic contact annealing improve the surface properties, as confirmed by deep level transient spectroscopy (DLTS), no surface trap being detected. The chemical reactivity of the metal with oxide and n-InP is important to the formation of Schottky barriers. The reactive metals Al and Ni gave a low barrier height due to the reduction of oxide and reaction with InP. Nonreactive metals Au and Pd gave a high barrier height. The modified thermionic emission (TE) theory and thermionic field emission (TFE) theory can be used to explain the conduction mechanisms on Ni and Au MIS diodes. The Pd MIS diode exhibited an excess current component at low forward bias due to surface states which predominate at low temperature.