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

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 (Vo) 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 Vo 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 Vo in ZnO at a low temperature, and it could be beneficial for the preparation of p-type ZnO films.