PHOTOELECTROCHEMICAL PROCESSING OF SEMICONDUCTORS

When immersed in an electrolyte, a semiconductor undergoes an exchange of electrons with the liquid at the interface to equalize the work functions of the two phases. The result is often a rectifying barrier between the semiconductor and liquid that has properties similar to a Schottky barrier. Like semiconductor-metal contacts, the barrier height can be fixed by the semiconductor surface state distribution, or, in the case of a low density of surface states, by the difference between the work functions of the bulk semiconductor and the liquid. Similarly, a reaction between the semiconductor surface and the eiectrolyte can produce a surface layer that fixes the barrier height. 

The contact barrier that is produced is characterized by a bending of the semiconductor s conduction and valence bands. Such barriers are 

Light-localized, wet processing of semiconductors which is not photoelectrochemical in nature is also known. Localized surface heating can reduce the overpotential for electroplating (2) or accelerate etching, for example. In addition, reactive intermediates can be produced by photolysis of electrolyte species (e.g., Brg), which then go on to react chemicaiiy with the semiconductor surface (3). These nonphotoelectro-chemicai approaches will not be dealt with further in this chapter. 

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Fujishima, A., Narasinga Rao, T., and Ohko, Y., Photoelectrochemical processes of semiconductors, in Photocatalysis, Science and Technology, Kaneko, M. and Okura, I. (Eds), Kodansha/Springer, Berlin, 2002, Chap. 2. 

Figure 1. Cell design and semiconductor mounting for iaboratory investigations of photoelectrochemical processing of semiconductors.

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