CHLORINATION AND PHOTODESORPTION ON SI(100) AND SI(111)

The surface parameters controlling the dynamics of SiCl(x) (x = 1-4) c hlorination and photodesorption by near UV irradiation from doped Si(1 11) and Si(100) have been studied as a function of crystallography and carrier concentration. Significant variations in desorption yield wer e found for the Si(100) and Si(111) samples with type and level of the sample doping (specific conditions: (1) low chlorine pressures, 1 X 1 0(-6) Torr, and (2) low laser fluence, 30 mJ/cm2). The SiCl(x) (x = 1- 4) desorption yields are best interpreted in terms of a mechanism in w hich photoexcitation couples the effect of carrier doping level with s urface chlorine coverage. The dependence of the yields on these two va riables is analyzed in terms of a model which balances the surface cha rge production of holes with the surface chlorine coverage.