Physical nature of the InP near-surface defect acceptor and donor states

The initial stage [0.00130 monolayers (ML)] of room-temperature Schottky-barrier formation of In on n- and p-type InP(110) interfaces has been studied by photoemission using a newly designed ultralow-coverage metal evaporator which can reproducibly evaporate metals with coverages as low as 0.0001 ML. It is found that the In/n-type InP(110) interface band bending does not start until the In coverage reaches about 0.3 ML, while the In/p-type InP(110) band bending is almost saturated at 0.3 ML. The heating effect on the band bending of clean cleaved n- and p-type InP(110) surfaces is also studied by using photoemission. It is found that heating has an irreversible band-bending effect on the p-type InP(110) but not on the n-type InP(110) interface. Based on these two striking differences in the band-bending behavior of n- and p-type InP, it is proposed that the physical nature of InP near-surface defect acceptor and donor levels may be different. (Our results are discussed and compared with calculated defect levels of Daw and Smith [Solid State Commun. 37, 205 (1981)] and Allen and Dow [Phys. Rev. B 25, 1423 (1982)]).