ch aPTer 8 eLecTricaL measuremenTs
Matthew D. McCluskey, Eugene E. Haller · 2012
Applications require control of semiconductor properties such as dopant and deep-level concentrations, compensation, point and line defects, and lifetime of minority carriers. These properties can be determined only if sufficiently sensitive and reliable analytical techniques are available. A good characterization method should allow the direct and independent measurement of a given property. In addition, one often wants to know exactly what is causing a semiconductor crystal to exhibit a certain property (e.g., which impurity-phosphorus, arsenic, or antimony-is making a silicon crystal n-type). The range of characterization techniques and their level of sophistication are truly impressive. This sophistication has been possible in large part because of the development of more complex instrumentation-instruments that use, among other components, improved semiconductor materials. Characterization is therefore an essential part of the feedback loop that continually improves technology. In the following chapters, a range of characterization methods will be discussed. While the discussion is not all-inclusive, we have highlighted the most widely used methods for characterizing defects in semiconductors. The techniques are grouped into electrical measurements (Chapter 8), optical measurements (Chapter 9), particle-beam methods (Chapter 10), and microscopy (Chapter 11). Additional information about semiconductor characterization may be found in books such as Kane and Larrabee (1970), Stavola (1998), and Schroder (2006). In this chapter, we discuss the basics of electrical transport, followed by specific techniques for determining resistivity and free-carrier concentration. After a brief review of p-n and Schottky junctions, techniques utilizing capacitance-voltage and transient capacitance measurements are discussed. Deep-level transient spectroscopy is an especially popular technique that uses capacitive transients to characterize carrier traps. Minority carrier lifetime measurements, important for a range of device applications, are summarized. We conclude with a brief discussion of techniques that use the thermoelectric effect to characterize deep levels.