Evaluation of Various Electrode Metals for Ultra-High Purity P-Type Si Surface Barrier Detectors

Metal contacts on UHP p-Si were experimentally investigated. Au was evaporated at the back face of a UHP p-Si wafer to form the ohmic contact. On its front face, electrodes of 11 different metals-Pd, Ag, Au, Ni, Bi, Pb, Sn, Al, Mn, Mg and Sm were evaporated with each electrode area of 0.5 cm2, and the detector characteristics were measured. Mg, Al, Sn and Mn showed satisfactory characteristics as the barrier metal; and Pd, Au and Ni as the ohmic contact metal. Obvious correlation is observed between current characteristics and metal work function values. Carrier injection in totally depleted detectors were also studied for several back contact metals.