Thin film technology based on hydrogenated amorphous silicon

Abstract

Hydrogenated amorphous silicon and related alloys represent a special type of thin film semiconductor material that has attracted much attention in the last decade. The scientific and technological properties of these materials include a continuously adjustable band gap, reasonable carrier lifetime and drift length, efficient optical transitions, and the possibility of their n- or p-type doping during the deposition process. The films can be easily fabricated with low costs by different chemical and physical vapour deposition methods which will be reported in some detail in this review. The importance of defect passivation and its influence on the density of states will be discussed together with the dependence of the material properties on preparation techniques and conditions. The second part of the review covers applications in devices and limitations due to the creation of metastable defects in these materials, the so-called Staebler-Wronski effect. A short overview will be given about the principle, structures and function, advantages and state of development of the main applications such as solar cells, thin film (field effect) transistors, electrophotography devices, image sensors, memory switches, and light-emitting devices.