Nitrogen-hydrogen complexes in ZnO: A possible route toward p-type conductivity.

Zinc oxide (ZnO) is a wide band gap II-VI semiconductor with optical, electronic, and mechanical applications. The lack of reliable $p$-type doping, however, has prevented it from competing with other semiconductors such as GaN. In this talk, I describe the successful incorporation of nitrogen-hydrogen (N-H) complexes in ZnO during chemical vapor transport (CVT) growth, using ammonia as an ambient. The N-H bond-stretching mode gives rise to an infrared (IR) absorption peak at 3150.6 cm$^{-1}$. Isotopic substitutions for hydrogen and nitrogen result in the expected frequency shifts, thereby providing an unambiguous identification of these complexes. The N-H complexes are stable up to $\sim $700\r{ }C. The introduction of neutral N-H complexes could prove useful in achieving reliable $p$-type conductivity in ZnO.