Unambiguous identification of nitrogen-hydrogen complexes in ZnO

Abstract

Zinc oxide (ZnO) is a wide-band-gap semiconductor with a range of potential applications in optoelectronics. The lack of reliable $p$-type doping, however, has prevented it from competing with other semiconductors such as GaN. In this Brief Report, we report the successful incorporation of nitrogen-hydrogen (N-H) complexes in ZnO during chemical vapor transport growth, using ammonia as an ambient. The N-H bond-stretching mode gives rise to an infrared absorption peak at $3150.6\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. Substitutions of deuterium for hydrogen and $^{15}\mathrm{N}$ for $^{14}\mathrm{N}$ result in the expected frequency shifts, thereby providing an unambiguous identification of these complexes. The N-H complexes are stable up to $\ensuremath{\sim}700\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. The introduction of neutral N-H complexes could prove useful in achieving reliable $p$-type conductivity in ZnO.