Increase fixed charge at Al2O3/Ga2O3 interface for high-performance Ga2O3 trench Schottky barrier diodes by atomic nitrogen treatment
Shubo Wei, Zifan Hong, Chengchao Li, M T Long, Ying Li, Y. B. Chen, Feng Zhang, Weifeng Yang
Abstract
We demonstrate a significant improvement in the breakdown voltage of vertical β-Ga2O3 metal-insulator-semiconductor (MIS) trench Schottky barrier diodes (TSBDs) through atomic nitrogen treatment at the Al2O3/β-Ga2O3 interface. The treated TSBDs show a breakdown voltage increasing from 832 to 1200 V while maintaining a low turn-on voltage of 0.9 V and a low specific on-resistance of 12.1 mΩ cm2. As indicated by the x-ray photoelectron spectroscopy analysis, atomic nitrogen treatment reduces oxygen vacancies on the β-Ga2O3 surface and promotes the formation of ternary Ga–O–N compounds at the Al2O3/Ga2O3 interface. These compounds passivate ICP (Inductively Coupled Plasma)-induced defects on the Ga2O3 trench surface, reducing the leakage current in the Al2O3/Ga2O3 MIS TSBDs. Meanwhile, the atomic nitrogen treatment induces a positive shift in the flatband voltage of Ga2O3 MOS capacitors with Al2O3 dielectric, a sign of an increase in the fixed charge density (Q1) at the Al2O3/Ga2O3 interface, which expands the depletion region under reverse bias and strengthens the contact barrier. These findings testify to the fact that atomic nitrogen treatment effectively optimizes the trench MIS interface, promising to an effective strategy for high-performance Ga2O3-based Schottky barrier diodes.