Oxygen vacancy-passivated ZnO thin film formed by atomic layer deposition using H2O2

Intrinsic defect oxygen vacancies, which can easily form in ZnO films and result in a compensation effect on p-type dopants, have long prevented the preparation of high-quality p-type ZnO; consequently, the application of ZnO in optoelectronic devices has been adversely affected. Therefore, in this investigation, the passivation of oxygen vacancies in undoped ZnO using H2O2 as an oxygen source is studied using atomic layer deposition (ALD). The ALD growth window ranged from 60 to 150 °C, and the use of H2O2 as an oxygen source, instead of H2O, changed the preferred growth orientation from coexisting a- and c-axes to only the c-axis, which indicated that H2O2 can provide an oxygen-rich environment for the growth of ZnO. Photoluminescence results indicated that oxygen vacancies in the ZnO film reduced significantly when H2O2 was used as the oxygen precursor instead of H2O for film preparation. Further, oxygen vacancies can be suppressed more efficiently using H2O2 when ZnO films were deposited at lower temperatures than at high temperatures. A decrease in the optical bandgap and an increase in the work function were observed when films were prepared using H2O2 due to a lowering of the Fermi level. Therefore, the use of H2O2 as an oxygen source is effective in providing an oxygen-rich environment and passivating oxygen vacancies in ZnO, which might be beneficial for the preparation of p-type ZnO films.