Vacuum, GaAs

ZnS, CdS, (ZnxCd x)S Hot-wall reactor,under active secondary vacuum Glass and III-V substrates, growth at 400 °C. ZnS poor-quality films. CdS and (ZnxCdi x)S good-quality films. CdS epitaxially growth on (lOO)-oriented GaAs and InP substrates 180... 

Lunt, S. R., Santangelo, P. G. and Lewis, N. S. Passivation of GaAs surface recombination with organic thiols. Journal of Vacuum Science Technology 9, 2333 (1991). 

Cross-sectional scanning tunneling microscopy (XSTM) measurements were carried out for a cleaved (110) surface of GaAs doped with Mn. The samples were cleaved in an ultrahigh vacuum (UHV) chamber in order to expose the atomically flat (110) surface. The measurements have been done in the UHV chamber at room temperature. 

This mcclianism is not so efrcctivc in polar semiconductors. The conversion of empty hybrids to doubly occupied hybrids on a GaAs surface would require the double occupation of a gallium hybrid, which is unfavorable because of the polar energy. Indeed, recent experiments (Chye, Babalola, Sukegawa, and Spicer, 1975) indicate that the I crmi level is not pinned on surfaces of GaP at the vacuum. Nonetheless, Schottky barriers can arise at GaP- metal interfaces. Metal-induced surface states" have been proposed as a mechanism (discussed in Section 18-1 ) but the barriers could well arise simply from incorporation of metal atoms in the semiconductor or vice versa. 

Fig. 34 are presented as ij-U-y curves. Without sulfide treatment a 1.05 eV band gap is resolved, whereas the gap shrinks completely after passivation. Though results seem in line with a passivation of electronic surface states by the sulfide treatment, since no band gap is resolved on clean GaAs(llO) in vacuum [53] , one may wonder whether the results of Fig. 34 a are not related to the overlayer instead of the substrate. Recent studies have indeed shown that the density of states is not reduced after sulfur coating [87], in contrast to initial assumptions [86]. Moreover, thermal desorption of the sulfide layer opens a band gap [164], as in Fig. 34 b, which is consistent with the existence of the monolayer of oxygen at the interface between GaAs and the layer [161]. In vacuum a wide band gap is also found locally at places where oxygen is adsorbed on clean GaAs(llO) [53]. 

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