Title :
Doping Asymmetry Problem in ZnO: Current Status and Outlook
Author :
Avrutin, Vitaliy ; Silversmith, Donald J. ; Morkoç, Hadis
Author_Institution :
Dept. of Electr. & Comput. Eng., Virginia Commonwealth Univ., Richmond, VA, USA
fDate :
7/1/2010 12:00:00 AM
Abstract :
ZnO has gained considerable interest recently as a promising material for a variety of applications. To a large extent, the renewed interest in ZnO is fuelled by its wide direct band gap (3.3 eV at room temperature) and large exciton binding energy (60 meV) making this material, when alloyed with, e.g., Cd and Mg, especially attractive for light emitters in the blue/ultraviolet (UV) spectral region. Unfortunately, as with other wide-gap semiconductors, ZnO suffers from the doping asymmetry problem, in that the n-type conductivity can be obtained rather easily, but p-type doping proved to be a formidable challenge. This doping asymmetry problem (also dubbed as the p-type problem in ZnO) is preventing applications of ZnO in light-emitting diodes and potential laser diodes. In this paper, we provide a critical review of the current experimental efforts focused on achieving p-type ZnO and discuss the proposed approaches which could possibly be used to overcome the p-type problem.
Keywords :
II-VI semiconductors; crystal symmetry; excitons; light emitting diodes; semiconductor doping; ultraviolet spectra; wide band gap semiconductors; zinc compounds; ZnO; blue-ultraviolet spectral region; doping asymmetry problem; electron volt energy 3.3 eV; electron volt energy 60 meV; exciton binding energy; laser diodes; light emitting diodes; n-type conductivity; temperature 293 K to 298 K; wide direct band gap semiconductors; Conducting materials; Conductivity; Excitons; Impurities; Light emitting diodes; Photonic band gap; Semiconductor device doping; Thin film transistors; Zinc compounds; Zinc oxide; $p$-type; Impurities; ZnO; point defects;
Journal_Title :
Proceedings of the IEEE
DOI :
10.1109/JPROC.2010.2043330