Abstract

Quantum dots (QDs), also called as nanocrystals, are a special class of semiconductor crystals that are composed of periodic groups of II–VI, III–V, or IV–IV materials, such as CdSe (Lee et al., 1998; Strassburg et al., 2000; Kratzert et al., 2001), InAs (Ebiko et al., 1998, 1999; Nakata et al., 2000; Yamaguchi et al., 2000; Joyce et al., 2001; Márquez et al., 2001; Krzyzewski et al., 2002; Migliorato et al., 2002; Bester and Zunger, 2003; Wasserman et al., 2003), InP (Seifert et al., 1996; Schmidbauer et al., 2002; Persson et al., 2003), and Ge QDs (Eaglesham and Cerullo, 1990; Kamins et al., 1997; Liu and Lagally, 1997; Ribeiro et al., 1998; Ross et al., 1998; Liu et al., 2000; Vailionis et al., 2000; Denker et al., 2001; Rastelli and Känel, 2002, 2003; Tersoff et al., 2002). Semiconductors derive their great importance from the fact that their electrical conductivity can be altered by adding an external stimulus, such as voltage. Therefore, semiconductors can be used to make critical parts of many different kinds of electrical circuits and optical applications. Semiconductor QDs, as a special structure, have their name because their small size causes quantum confinement and creates specific electronic states (Reithmaier et al., 2004; Badolato et al., 2005; Xu et al., 2007). Due to the quantum confinement and specific electronic states, QDs enable never before seen applications to science and technology.