Hydrogen-related complexes in Li-diffused ZnO single crystals

摘要

Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li_2O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (＞10~(19)cm~(-3)). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm~(-1), attributed to surface O-H species. When Li_2CO_3 is used, a structured blue luminescence band and O-H mode at 3327 cm~(-1) are observed at 10 K. These observations, along with positron annihilation measurements, suggest a zinc vacancy-hydrogen complex, with an acceptor level ～0.3eV above the valence-band maximum. This relatively shallow acceptor could be beneficial for p-type ZnO.