Energetics of photoexcited desorption from chlorinated Si(100) and Si(111)

Microscopic understanding of the photoetching of semiconductors on a molecular scale by halogens is essential in terms of defining initially the role of substitutional defects, charged carriers and band bending at the surface. Creation of charged carriers at high doping levels by photodionization coupled with field-induced transport introduces new reaction channels into the surface chemistry. This paper focusess on heavily doped Si(111) and Si(100) in the quantum mechanical regime at low laser fluences and surface temperatures where desorption is dominated by electron excitations [6]. Substantial alteration of the etching mechanism occurs when the atomic processes are driven quantum mechanically rather than thermally. Fundamental aspects are presented for this reaction regime where the surface chemistry is primarily electron-excited in terms of: (1) the influence of substitutional electron defects on the microetching and surface chemistry of heavily p- and n-doped Si(100) and Si(111) and, (2) photoexcited velocity distribution results at low laser fluences and temperatures. Some implications for the extension of these studies to energetic mechanisms for photodesorption are discussed.