Indium chalcogenide thin film semiconductor compounds In2X3 (with X being a chalcogen atom, i.e., S, Se, or Te) are important materials in many current technological applications such as solar cells, micro-batteries, memory devices, etc. This chapter reviews the recent progress in In2X3 (X = S, Se, or Te) thin film research and development, with a particular attention paid to their growth and processing methods and parameters, and the effects that these have on the films microstructure. The intimate relationship between their fabrication conditions and the resulting physico-chemical and functional properties is discussed. Finally, results pertaining to the fabrication and characterization of these thin film materials, as well as the main devices and applications based on them are also highlighted and discussed in this chapter.
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Remarkable advances have taken place during the past few decades in semiconductor materials and devices. The semiconductor compounds of In2X3 family, where X is S, Se or Te have attracted particular interest in recent years due to their promising technological applications including a wide variety of devices. Among the important In2X3 devices that have been developed are solar cells (Yu et al, 1998), dry cells (Dalas & Kobotiatis, 1993), photochemical cells (Hara et al, 2000), solid state batteries (Julien et al, 1985), phase change memory devices (Lee & Kang, 2005; Lee & Kim, 2005; Hirohata et al, 2006), thin film strain gauge (Desai et al, 2005a), gas sensors (Desai, et al, 2005b), etc. Some In2X3 compounds can be used in Schottky diodes, capacitors, heterojunctions, and micro batteries (Kobbi, B., et al, 2001), and they also have a potential application as passivating layer for III-V semiconductor devices (Barron 1997). Many of the devices based on In2X3 have already found their way into industry.
A number of books, book chapters, and topical reviews are dedicated to semiconductor compounds such as II-VI, III-V and group IV (Adachi, 2005; Ahrenkiel, 1993; Chu & Chu, 1995; Shay & Wernick, 1975). However there is no review on In2X3 semiconductor compounds available in the literature. This article reviews the status of research on In2S3, In2Se3 and In2Te3 thin films, and focuses on their fabrication methods and functional properties. It also summarizes the recent advances in their relevant applications in many devices.
The interest in In2S3 thin films has increased during the last decade or so because of the high potential demonstrated by this material. With optimal physical properties, this material can meet the requirements for use as a window material or a buffer layer for photovoltaic device structures (Barreau et al, 2003). In2S3 can be used as an effective replacement for CdS in Cu(In,Ga)Se2 (CIGS) based solar cells (Spiering et al, 2003). Though the highest conversion efficiency in thin film solar cells has been reported for CIGS with CdS buffer layer, it is desirable to replace CdS with cadmium free buffer layers for environmental reasons (Hariskos et al, 2005; Naghavi et al, 2003a; Naghavi et al, 2003b; Sakata, 2000; Lee, et al, 2007).