用CH_3CSNH_2钝化GaP表面特性的研究

Properties of GaP Surface Passivated with CH_3CSNH_2 Solution

借助扫描电子显微镜（ＳＥＭ）、Ｘ光电子能谱仪（ＸＰＳ）研究在不同处理条件下，ＧａＰ晶片表面硫化物钝化对其结构、形态以及表面形貌的影响。实验结果表明：经过ＣＨ３ＣＳＮＨ２溶液一定时间钝化处理后，ＧａＰ表面氧化物基本消失，形成薄的硫化物钝化层和较强的Ｇａ—Ｓ、Ｐ—Ｓ键，并引起Ｘ光电子能谱的Ｇａ、Ｐ芯能级化学位移，Ｇａ的硫化物有较好的稳定性。

The GaP surfaces were passivated with CH3CSNH2 solution of certain concentration at 90℃ temperature. The effect of passivation for different treatment time on the surface structure, morphology and electronic features was investigated using scanning electron microscopy(SEM) and X - ray photoelectron spectroscopy(XPS). First, the treatment time of about 20min. was determined to obtain a uniform passivation film on the GaP surface. This means that the wet chemical reactions were completed in a certain interval of time when the GaP wafer was dipped in the CH3CSNH2 solution. It is found that the oxide overlayer on the GaP surface has been removed basically. The chemical reaction between the Ga atoms and the S2- ions dissociated from the CH3CSNH2 solution has taken place under the condition of certain temperature. The XPS measuremnet results indicate that the gallium sulfide and phosphor us sulfide have been formed on the surface during the passivation. After passivation the XPS peaks of Ga 3d and P 2p are shifted to higher binding energy by about 0. 1 -0. 5 eV. 0. 2 0. 4eV from those of the bulk GaP and their full widths at half maximum(FWHMs) are increased, respectively. The P 2p band has been resolved into two component bands by a curve fitting technique. The fitted band peaked at 129. 2eV corresponds to free atom state of P, whereas the other fitted band peaked at 128. 5eV corresponds to compound state of P. These chemical shift are consistent with electronegativity and binding energy of sulfur. The passivated surfaces were further sputtered by Ar+ ion for 2min under the condition of voltage SKV, current density 100uA/cm2. It shows that the Ga 3d, P 2p, S 2p peaks are located at the binding energies of 18. 5eV, 129. 0eV, 158. 1eV, respectively. Hence it reveals that a thin S overlayer film has been formed on the GaP surface, which can prevent the oxidation from environment. It possesses a good chemical stability. The XPS measurements identify the presence of both Ga-S and P-S bonding.