Lowered stimulated emission threshold of zinc oxide by hydrogen doping with pulsed argon-hydrogen plasma

The effects of hydrogen doping on the optical and electrical properties of zinc oxide (ZnO) films were investigated. We prepared about 50-nm thick ZnO films on a sapphire substrate by using a pulsed laser deposition method and used a pulse-modulated inductively coupled plasma technique (PM-ICP) to intentionally insert hydrogen into the films. An increase in the electron concentration by hydrogen doping indicated that hydrogen is actually a cause of shallow donors. Moreover, the excitation intensity threshold for optically pumped stimulated emissions was significantly reduced after hydrogen doping.