“…The visibly transparent and short wavelength absorbing p-n junction is the basic device structure in order to fabricate light emitting and solid state UV laser diodes, transparent transistors for advanced active matrix flat panel displays and in solar cells for utilizing the UV component of Sun radiation [2][3][4]. However, almost all of the well-known transparent conducting oxides (TCOs) such as Al-doped ZnO [5,6], Sn-doped In 2 O 3 [7] and F-doped SnO 2 [8,9] are n-type semiconductor oxide, the lack of p-type TCOs severely limits the potential applications of these materials, because many of the active functions in semiconductors originate from the nature of the p-n junction.…”