Improved thermal processing of MOS diodes on n-InP

Metal-insulator-InP diodes with Al, Ni, Au, and Pd were fabricated using improved surface passivation techniques. The I-V and barrier height data indicate that a thin thermal oxide between the metal/InP and proximity cap protection during the rapid thermal annealing of the ohmic contact improve the surface properties as confirmed by deep-level transient spectroscopy, no surface trap being detected. The reactive metals Al and Ni gave a low barrier height due to the reduction of oxide and reaction with InP. The nonreactive metals Au and Pd gave a high barrier height. The modified thermionic emission theory and thermionic field emission 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, which may be due to interface states.