Low temperature method to passivate oxygen vacancies in un-doped ZnO films using atomic layer deposition

Highlights: •H₂O₂ was proved to provide more oxygen than H₂O for ALD growth of ZnO film. •The oxygen-rich condition of H₂O₂ can passivate the oxygen vacancy in ZnO film. •Vacancy decrease leads to carrier concentration decrease and resistivity increase. •H₂O₂ passivates oxygen vacancy efficiently at low temperature than high temperature. -- Abstract: Owing to oxygen vacancies, the as-prepared ZnO normally shows n-type semiconducting characteristic. This has restricted the preparation of high-quality p-type ZnO and the application of ZnO optoelectronic devices. Therefore, we studied a method of using H₂O₂ as an oxygen source to passivate oxygen vacancies (V_o) in ZnO films via atomic layer deposition (ALD). The temperature range for the self-limited growth of crystalline ZnO thin films by ALD using diethylzinc and H₂O₂ was found to be in the range of 80 to 150 °C. Our results show that the use of H₂O₂ as an oxygen source can provide an O-rich condition (instead of H₂O) for the growth of ZnO film, with a total preferential (002) orientation of the growth plane and decreased grain size. Further, the O-rich growth environment can suppress the formation of V_o and zinc interstitials and decrease the carrier concentration in ZnO (from 2.525 × 10¹⁹ cm⁻³ to 1.695 × 10¹² cm⁻³). This can lead to an increase in the film resistivity from 1.717 × 10⁻² Ω·cm for a ZnO film prepared using H₂O to 1.348 × 10⁴ Ω·cm for a ZnO film prepared using H₂O₂. Thus, H₂O₂ could be used to passivate V_o in ZnO at a low temperature, and it could be beneficial for the preparation of p-type ZnO films.