Dopants and Impurity-Induced Defects in ZnO

World Scientific
Publication Type:
Defects in Functional Materials, 2021, pp. 177-199
Issue Date:
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In recent years, there has been resurgent interest in ZnO due to its efficient UV emission and potential application in opto-electronic devices. The problem of self-compensating defects, especially those related to acceptor-like dopants, remains a major challenge to date. In this chapter, we provide an overview of the fundamental properties of point defects and dopants as well as their complexes in bulk crystals and nanostructures. Nominally undoped ZnO is typically n-type, which has been widely ascribed to O vacancies or Zn interstitials; however, these defect assignments are controversial as O vacancies are deep donors while Zn interstitials are highly mobile at room temperature and considered to be unstable. Accordingly, H and group III impurities have also been suggested to be responsible for the observed n-type conductivity. Although there are still many unanswered questions concerning defect-related luminescence bands in ZnO, great progress has been made in recent years to identify and characterize them using spatially resolved luminescence spectroscopies and first-principles calculations. The ubiquitous green emission has several possible origins, including O and Zn vacancies as well as Cu impurities. The properties of group I (Li, Na, and Cu), group III (Ga, Al, and In), and group V (N, P, and Sb) impurities as well as their complexes with native point defects and H are discussed, along with a concluding outlook for future research into the optical properties of ZnO.
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