Effect of oxygen vacancies in heteroepitaxial β-Ga2O3 thin film solar blind photodetectors

In this work, β-Ga2O3 thin films were deposited on GaN template and sapphire substrates by metal-organic chemical vapor deposition (MOCVD), respectively. Corresponding β-Ga2O3 thin film metal-semiconductor-metal (MSM) photodetectors (PDs) were prepared. Comparing the performance between these two heteroepitaxial β-Ga2O3 thin film PDs, oxygen vacancies were found to determine the discrepancy. The responsivity of β-Ga2O3 PDs on GaN increased with interdigital spacing, while the behavior of β-Ga2O3 PDs on sapphire was opposite. A photoconductive model of MSM structure was announced, showing the key role of oxygen vacancies in above observation. Meanwhile, the capture of photogenerated holes by oxygen vacancies not only enhanced the responsivity but also delayed the response time. This work paved the way for further optimization of heteroepitaxial β-Ga2O3 thin film PDs.