【Domestic Papers】The effect of O₂ high-temperature annealing on the quality of Al₂O₃/Ga₂O₃ interface

      Ultrawide-bandgap semiconductor gallium oxide (β-Ga₂O₃), owing to its extremely high critical breakdown field and the potential for large-size substrate preparation, shows tremendous application prospects in next-generation ultra-high-power electronic devices. In β-Ga₂O₃ MOSFETs, the metal–oxide–semiconductor capacitor (MOSCAP) is the core structure of the device. However, poor metal–oxide–semiconductor (MOS) interface quality and high interface state density severely limit the realization of high-performance MOSFETs.

      Traditional β-Ga₂O₃ surface pretreatment methods, such as Piranha, BOE, and HF wet chemical processes or O₂, CF₄, and N₂ plasma treatments, involve complex procedures, high costs, and limited improvement effects, and may even damage the β-Ga₂O₃ surface. Therefore, the development of an efficient and low-cost surface passivation technology has become an urgent demand in this field.

      In this study, we employed a simple and low-cost thermal treatment technique to pretreat the β-Ga₂O₃ surface. Specifically, a short-time high-temperature annealing process at 1300 K in a high-purity oxygen atmosphere was used to introduce oxygen atoms into the surface of Ga₂O₃ crystals, thereby filling oxygen vacancies and passivating the Ga₂O₃ surface. The fabricated Al₂O₃/Ga₂O₃ MOSCAP exhibited a low interface trap density (Dit) of approximately 1.6 × 10¹¹ cm⁻²·eV⁻¹, as well as a low-frequency-dependent flat-band voltage shift (ΔVFB(f)) of about 40 mV (from 1 kHz to 1 MHz).

Figure 1 (a) Schematic structure of the vertical Ga₂O₃ MOS capacitor. (b)–(d), (f), (g) High-resolution TEM images of the Al₂O₃/Ga₂O₃ interface for the experimental samples. (e), (h) First-principles calculations of the d(001) interplanar spacing of the β-Ga₂O₃ unit cell. (i), (j) C–V curves of the samples at frequencies from 1 kHz to 1 MHz. (k) Frequency dispersion characteristics of the samples in the accumulation region.

Figure 2 (a) Forward VFB extracted from C–V curves at measurement temperatures of 298, 398, and 473 K. (b) Forward ΔVFB(f) extracted from C–V curves at 298, 398, and 473 K, where ΔVFB(f) denotes the flat-band voltage shift as the test frequency increases from 1 kHz to 1 MHz. (c) Relationship between the characteristic response frequency f of electrons and the trap energy level (ECB − ET) of the sample in the temperature range of 300–475 K. (d) Relationship between the interface trap density Dit and the trap energy (ECB − ET) of the sample.

Team Introduction

      Prof. Xinke Liu is the Director of the Institute for Power Semiconductor Devices and AI Energy Monitoring Engineering Technology at Shenzhen University, a researcher at the School 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 a doctoral supervisor. He has long been engaged in research on wide-bandgap semiconductor gallium nitride (GaN) materials and devices. He has published 121 SCI papers as first or corresponding author in international journals such as Materials Today, Advanced Materials, and IEEE EDL/TED. He has also presented 28 papers at top international journals and conferences such as IEDM, ISPSD, IEEE EDL/TED, APL, and JAP.

      Prof. Liu has led major research projects including the National Key R&D Program of China, National Natural Science Foundation of China (Young and General Programs), and the Guangdong Natural Science Foundation Distinguished Young Scholar Project. As the first contributor or individual recipient, he has won the Bronze Award at the 2021 Guangdong University Science and Technology Achievement Transformation Final, the Second Prize of the Guangdong Science and Technology Progress Award (2022), the Second Prize of the Science and Technology Progress Award of the Chinese Institute of Electronics (2022), the Second Prize of the Guangdong Institute of Electronics Science and Technology Progress Award (2022), and the Shenzhen Youth Science and Technology Award (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