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Ultra-wide bandgap semiconductor gallium oxide (β-Ga2O3) shows great application prospects in the next generation of ultra-high power electronic devices due to its extremely high critical breakdown field strength and the potential for large substrate fabrication. Inβ-Ga2O3 MOSFET devices, the metal-oxide-semiconductor capacitor (MOSCAP) is the core structure of the device, but it faces issues of poor metal-oxide-semiconductor (MOS) interface quality and high interface state density, severely limiting the realization of high-performance MOS field-effect transistors (MOSFETs).
Traditional surface pretreatment methods forβ-Ga2O3 such as Piranha, BOE, HF wet chemical treatments, or O2, CF4, N2 plasma treatments are complex, costly, and have limited improvement effects, and may even damage the surface ofβ-Ga2O3 surface. Therefore, developing an efficient and low-cost surface passivation technology has become an urgent need in this field.
This study employs a simple and low-cost thermal treatment technique to pretreat the surface ofβ-Ga2O3 surface. This technique introduces oxygen atoms into the Ga2O3 crystal surface to fill the oxygen vacancies on the Ga2O3 crystal surface through a high-temperature short-time annealing process at 1300K in a high-purity oxygen atmosphere, passivating the Ga2O3 surface. The prepared Al2O3/Ga2O3 MOSCAP exhibits a low interface trap density (Dit) of about 1.6×1011 cm-2 eV-1. It shows a low-frequency dependent flatband voltage shift (ΔVFB( f ) of about 40 mV (from 1 kHz to 1 MHz).
Figure 1 (a) Schematic diagram of the vertical Ga2O3 MOS capacitor structure (b) (c) (d) (f) (g) are high-resolution TEM images of the experimental group samples at the Al2O3/Ga2O3 interface (e) (h) are evaluations of theβ-Ga2O3 unit cell’s d(001) interplanar spacing using first-principles calculations (i) (j) are the C-V curves of the samples at frequencies from 1kHz to 1MHz (k) frequency dispersion characteristics of the samples in the accumulation region.
Figure 2 (a) ForwardVFB extracted from C-V curves at measurement temperatures of 298, 398, and 473K (b) Forward ΔVFB( f ) extracted from C-V curves at temperatures of 298, 398, and 473K, where ΔVFB ( f ) is the flatband voltage shift when the test frequency increases from 1 kHz to 1 MHz. (c) The characteristic response frequency f of electrons at temperatures (300K~475K) as a function of the sample trap energy level(ECB – ET) (d) The relationship between interface trap densityDit and the sample trap energy (ECB – ET).
Team Introduction
Xinke Liu, Director of the Power Semiconductor Devices and AI Energy Monitoring Engineering Research Institute at Shenzhen University, Researcher at the College of Materials and the National Key Laboratory for RF Heterogeneous Integration, Fellow of the Institute of Physics (FInstP, 2025), Fellow of the Royal Society of Chemistry (FRSC, 2024), and PhD supervisor. He has been engaged in research on wide bandgap semiconductor gallium nitride materials and devices, publishing 121 SCI papers as the first author or corresponding author in international academic journals such asMaterials Today, Advanced Materials, IEEE EDL/TED, and has published a total of 28 articles in well-known international academic journals/top conferences such as IEDM, ISPSD, IEEE EDL/TED, APL, JAP. He has led important research projects such as the National Key R&D Program of the Ministry of Science and Technology, the National Natural Science Foundation (Youth and General), and the Outstanding Youth Project of the Guangdong Provincial Natural Science Foundation. As the first contributor or individual, he has received the Bronze Award in the 2021 Guangdong Provincial University Science and Technology Achievement Transformation Finals, the Second Prize for Scientific and Technological Progress in Guangdong Province in 2022, the Second Prize for Scientific and Technological Progress from the China Electronics Society in 2022, the Second Prize for Scientific and Technological Progress from the Guangdong Provincial Electronics Society in 2022, and the Shenzhen Youth Science and Technology Award in 2023.
Article Information
The effect of O2 high-temperature annealing on the quality of Al2O3/Ga2O3 interface
Chunyan Chen; Yutong Wu; Bing Jiang; Zhixiang Zhong; Fan Yang; Xinke Liu
Appl. Phys. Lett. 127, 061602 (2025)
https://doi.org/10.1063/5.0284936
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