Study Of Surface Properties Of GaP Semiconductors Passivated By Sulfur Treatment

In recent years III-V compound semiconductor have been practically applied to electronic and optoelectronic devices. Many kinds of 1II-V metal semiconductor field-effect transistors (MESFET's) are used as a key device in portable telephones. However, surfaces states degrade the performance of MESFET's. Therefore, it is of great importance to develop process technology for surface passivation. In this aspect, there have been reported that a surface treatment with sulfur is effective in reducing the surface state density.In this paper, the GaP wafer surfaces were passivated with CH3CSNH2 solution of certain concentration at 90 ?2癈 temperature. The effect of passivation for different time on the surface structure, morphology and electronic features was investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We also investigated the photoluminescence (PL) characteristics of GaP after it was treatedThe XPS measurement results indicate that the gallium sulfide and phosphorus sulfide have been formed on the surface during the passivation. It is found that the XPS peaks of the Ga3d, Ga2p and P2p are shifted to higher binding energy compared with the untreated sample and the results are similar to other foreign correlative work. The passivated surfaces were further sputtered by Ar+ ions for 8min under the condition of voltage 5kV, current density 100(jA/cm2. It shows that the Ga3d, Ga2p and P2p peaks are located at the lower binding energies compared with unsputtered samples. The XPS analysis results also reveal that the surface oxide compound of GaP has removed basically, especially from the strength change of Ols core level. Hence it implied that a thin S overlayer has been formed on the GaP surface, which can prevent the oxidation from environment. It possesses a good chemical stability.The SEM observation appeared that the treatment time by CH3CSNH2 solution for 20min is determined to obtain a uniform passivation film on the GaP surface compared with other treatment time, this means that the wet chemical reactions were completed in a certain interval of time when GaP wafer was dipped in the CH2CSNH3 solution. The chemical reaction between the Ga atoms of GaP surface and the S2" ions dissociated from the CH3CSNH2 solution has taken place under the condition of certain temperature. From the measurement results of XPS and SEM, the possible passivated mechanism of CH3CSNH2 solution to GaP surfaces is also discussed.The PL measurement results reveal that the photoluminescent intensity of treatment sample is improved greatly, especially the treatment time is 25min. it indicate the reduction of surface combination velocity of GaP, resulting in the reduction of surface defect states due to the formation of sulfur passivation films.