【International Papers】Electrical and structural characterization of in situ MOCVD Al₂O₃/β-Ga₂O and Al₂O₃/β-(AlₓGa₁₋ₓ)₂O₃3 MOSCAPs

      Researchers from the The Ohio State University have published a dissertation titled "Electrical and structural characterization of in situ MOCVD Al₂O₃/β-Ga₂O₃ and Al₂O₃/β-(Al_xGa_1−x)₂O₃ MOSCAPs" in Journal of Applied Physics.

Abstract

      This study investigates the electrical and structural properties of metal–oxide–semiconductor capacitors (MOSCAPs) with in situ metal-organic chemical vapor deposition-grown Al₂O₃ dielectrics deposited at varying temperatures on (010) β-Ga₂O₃ and β-(Al_xGa_1−x)₂O₃ films with different Al compositions. The Al₂O₃/β-Ga₂O₃ MOSCAPs exhibited a strong dependence of electrical properties on Al₂O₃ deposition temperature. At 900 °C, reduced voltage hysteresis (∼0.3 V) with improved reverse breakdown voltage (74.5 V) was observed, corresponding to breakdown fields of 5.01 MV/cm in Al₂O₃ and 4.11 MV/cm in β-Ga₂O₃ under reverse bias. In contrast, 650 °C deposition temperature resulted in higher voltage hysteresis (∼3.44 V) and lower reverse breakdown voltage (38.8 V) with breakdown fields of 3.69 and 2.87 MV/cm in Al₂O₃ and β-Ga₂O₃, respectively, but exhibited impressive forward breakdown field, increasing from 5.62 MV/cm at 900 °C to 7.25 MV/cm at 650 °C. High-resolution scanning transmission electron microscopy (STEM) revealed improved crystallinity and sharper interfaces at 900 °C, contributing to enhanced reverse breakdown performance. For Al₂O₃/β-(Al_xGa_1−x)₂O₃ MOSCAPs, increasing Al composition (x) from 5.5% to 9.2% reduced net carrier concentration and improved reverse breakdown field contributions from 2.55 to 2.90 MV/cm in β-(Al_xGa_1−x)₂O₃ and 2.41 to 3.13 MV/cm in Al₂O₃. The electric field in Al₂O₃ dielectric under forward bias breakdown also improved from 5.0 to 5.4 MV/cm as Al composition increased from 5.5% to 9.2%. The STEM imaging confirmed the compositional homogeneity and excellent stoichiometry of both Al₂O₃ and β-(Al_xGa_1−x)₂O₃ layers. These findings demonstrate the robust electrical performance, high breakdown fields, and excellent structural quality of Al₂O₃/β-Ga₂O₃ and Al₂O₃/β-(Al_xGa_1−x)₂O₃ MOSCAPs, highlighting their potential for high-power electronic applications.