Iodine treatment of semiconductor surfaces

用X射线光电子能谱研究了NH_4I处理的GaAs和CuInS_2表面，用单色化Al K α X射线光电子能谱测量了浸泡在NH_4I水溶液中的GaAs衬底。我们从Ga 3d谱中发现了镓的三种化学状态：（a）来自GaAs的峰，（B）比GaAs的峰深0.9 eV的峰，和（c）深1.6 eV的峰。虽然峰（B）可以是碘化镓的峰，但至少峰（c）被认为是氧化镓，这不能通过调节处理参数来避免。用NH_4I处理的GaAs在真空中加热。碘化物以及氧化物从表面上除去。然而，碘化物比氧化物更早升华。因此，我们认为NH_4I处理不足以避免GaAs表面的氧化。我们还研究了NH_4I处理的GaAs表面的电学性质。用NH_4I溶液在CuInS_2上存款CdS，也能除去CuInS_2表面的Cu氧化物。

GaAs and CuInS_2 surfaces treated with NH_4I have been studied by X-ray photoemission spectroscopy.GaAs substrate dipped in an aqueous solution of NH_4I was measured by XPS using monochromatized Al Kalpha x-ray. We found three chemical states of gallium from the Ga 3d apectra : (a) peaks from GaAs, (b) peaks which are 0.9 eV-deeper than those of GaAs, and (c) peaks which are 1.6 eV-deeper. Although the peaks (b) may be that of gallium iodide, at least the peaks (c) are considered to be gallium oxide, which can not be avoided by adjusting treatment paremeters. When the GaAs treated with NH_4I is heated in vacuum. iodide as well as oxide is removed from the surface. The iodide, however, sublimates earlier than the oxide. We thus conclude that the NH_4I treatment is not enough to avoid an oxidation of GaAs surfaces. We also studied the electrical properties of the NH_4I-treated GaAs surfaces. No significant change has been observed in the Schotkey barrier height.NH_4I solution, which is used to deposit CdS on CuInS_2, does also remove Cu oxide from CuInS_2 surface.