supported by the National Basic Research Program of China(2012CB933703);the National High Technology Research and Development Program of China(2006AA03Z311);the National Natural Science Foundation of China(51172041,91233204 and 51372035);the Program for New Century Excellent Talents in University(NCET-11-0615)
Wide bandgap(3.37 eV)and high excitonbinding energy of ZnO(60 meV)make it a promising candidate for ultraviolet light-emitting diodes(LEDs)and low-threshold lasing diodes(LDs).However,the difficulty in producing stabl...