Metal reactivity effects on the surface recombination velocity at InP interfaces

Direct measurements of the surface recombination velocity (SRV) on etched InP(110) and at its interfaces with various metals deposited by thermal evaporation have been performed using ultrafast time-resolved photoluminescence. The results show that the original InP low SRV is retained when these surfaces are coverd with metals which tend to react with the semiconductor's anion, such as Al, Cr, and Zn. On the other hand, the SRV increases sharply as a function of unreactive metal coverage, such as Cu, Au, and Ag. The SRV results are explained in terms of metal-induced interface states, whose position in the band gap and thus their cross section for recombination depends on the metal reactivity. The similarity of the SRV and the reported Schottky barrier height dependence on the metal-phosphorus heat of reaction is noted.