Silicon, amorphous, electronic properties

Electronic defects reduce the photosensitivity, suppress doping and impair the device performance of a-Si H. Their high density in pure amorphous silicon makes this material of lesser interest and is the reason for the attention on the hydrogenated material, in which the defect density is greatly reduced. The remaining defects in a-Si H control many electronic properties and are centrally involved in the substitutional doping process. The phenomena of metastability, which are described in Chapter 6, are caused by the defect reactions. 

This book describes the properties and device applications of hydrogenated amorphous silicon. It covers the growth, the atomic and electronic structure, the properties of dopants and defects, the optical and electronic properties which result from the disordered structure, and finally the applications of this technologically very important material. There is also a notable chapter on contacts, interfaces, and multilayers. The main emphasis of the book is on the new physical phenomena which result from the disorder of the atomic structure. 

Car, R., and M. Parrinello (1988). Structural, dynamic, and electronic properties of amorphous silicon an ab initio molecular dynamics study. Phys. Rev. Lett. 60, 204-7. 

Car, R., and Parrinello, M. (1988) Stinctmal, Djmianical, and Electronic Properties of Amorphous Silicon An ab initio Molecular-Dynamics Study, Phys. Rev. Lett. Vol. 60, pp.204-207. 

W. E. Spear and S. H. Baker, Electronic properties of metal-amorphous silicon barriers andjunctions, Electrochim. Acta 34(12), 1691, 1989. 

Disordered covalent materials such as amorphous silicon, hydrogenated amorphous silicon, amorphous carbon, and diamondlike carbon are of current interest because they are important in technological applications. The TBMD scheme will be very useful in the study of the microscopic structural, dynamical, and electronic properties of these complex systems. 

Among liquids that may exhibit a liquid-liquid phase transition, a feature, that is, special to silicon (though not uniquely so see earlier discussions) is the change in electronic properties that accompany the liquid-liquid phase transition. Indeed, this is a feature that has been exploited in studies from early on in experimental probing of the transition. The amorphous-amorphous transition in silicon has been also found to be a transition from a semiconducting low-density state to a metallic high-density state. The liquid form of these phases has shown similar change in the... 

The presence of hydrogen in amorphous silicon alloys affects both the defect structure and the instabilities. Specific examples where the presence of hydrogen is either directly or indirectly important include (1) the elimination of silicon dangling bonds, (2) the trapping of molecular hydrogen in voids and (3) the presence of optically-induced, reversible metastabilities in the optical and electronic properties. 

Street, D.K. Biegelsen and J.C. Knights, Defect States in Doped and Compensated a-Si H, Phys. Rev. B24 969 (1981). dler, Electronic Properties of Amorphous Silicon Alloys, Kinam 4C 225 (1982). ... 

In the early 1970s, Spear and coworkers (Spear, 1974 Le Comber et al., 1974), although unaware of the presence of hydrogen, demonstrated a substantial reduction in the density of gap states (with a corresponding improvement in the electronic transport properties) in amorphous silicon films that were deposited from the decomposition of silane (SiH4) in an rf glow discharge. 

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