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-Kalpha X-射线对浸泡在NH_4I水溶液中的GaAs衬底进行了XPS测量。我们从Ga3d谱中发现了镓的三种化学态：(A)来自GaAs的峰，(B)比GaAs深0.9 eV的峰，和(C)深1.6 eV的峰。虽然(B)峰可能是碘化镓的峰，但至少(C)峰被认为是氧化镓，这是通过调整处理参数无法避免的。用NH_4I处理的砷化镓在真空中加热。碘化物和氧化物被从表面除去。然而，碘化物比氧化物更早升华。因此，我们得出结论，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。在CuInS_2表面沉积Cd的NH_4I溶液也能去除CuInS_2表面的氧化铜。

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.