ABSTRACT
ABSTRACT This chapter concerns the electrodeposition of compound semiconductors. That compound semiconductors can be electrodeposited is well known. Questions being addressed by this group concern the limits to compound electrodeposit quality that can be achieved. Can epitaxial deposits be formed? Under what conditions can they be formed, and with what types and numbers of defects? This chapter briefly describes a number of compound electrodeposition methodologies that have been used to form devices, such as high-efficiency photovoltaics. The chapter then elaborates on the method of electrochemical atomic layer epitaxy (ALE). Electrochemical ALE is based on the use of surface limited electrochemical reactions, known as underpotential deposits (UPD), to form atomic layers of the elements making up a compound, individually, in a cycle. Each cycle of deposition forms a monolayer of the compound, and the number of cycles determines the deposit thickness. In principle, using surface limit reactions to form each atomic layer should prevent three-dimensional growth and promote epitaxy. Thin films have been formed using this technique in an automated electrochemical thin-layer flow cell system. Electrochemical ALE is, presently, a relatively slower methodology, and there are a number of automation issues to be resolved, some of which are discussed in this chapter. One of the main reasons for studying electrochemical ALE, however, is that it results in the deconvolution of compound electrodeposition into a series of individually tractable steps, studies of which should benefit understanding of the limits and mechanisms of compound electrodeposition in general. Studies of these steps have been pursued using surface-sensitive spectroscopes and scanning probe techniques.
