ABSTRACT
ZnO, which is a wide bandgap (∼3.37 eV) semiconductor, has a high exciton binding energy of ∼60 meV [1]. Furthermore, ZnO is an inexpensive, relatively abundant, chemically stable, easy to prepare, and nontoxic material. Therefore, ZnO has been recognized to be a promising candidate for the fabrication of low-cost ultraviolet (UV) optoelectronic devices. One of the most promising applications of ZnO is to replace indium tin oxide (ITO) in the displays and photovoltaic panels due to the low cost of transparent conductors. In addition, due to the conductive nature of ZnO, it has the potential to be used as the semiconductor materials for making of inexpensive UV optoelectronic devices such as UV laser diodes. Nevertheless, there are not more than 10 original reports on the realization of UV ZnO laser diodes that have been published during the past decade [2-11]. This may be due to two technical challenges that need to be overcome before ZnO can be fully utilized to fabricate UV laser diodes.
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