Key Takeaways & Executive Findings
- •• Fabrication of vertical SnO/β-Ga2O3 heterojunction diode via RF reactive magnetron sputtering. • Determination of type-II band alignment with valence and conduction band offsets of 2.65 eV and 0.75 eV, respectively. • Enhanced reverse blocking characteristics with breakdown voltage of 1675 V and power figure of merit of 1.0 GW/cm² compared to Schottky barrier diode. • TCAD simulation shows that SnO film depresses electric field crowding at the anode edge, indicating potential for high-performance power devices.
Abstract
In this study, we present the fabrication of vertical SnO/β-Ga2O3 heterojunction diode (HJD) via radio frequency (RF) reactive magnetron sputtering. The valence and conduction band offsets between β-Ga2O3 and SnO are determined to be 2.65 and 0.75 eV, respectively, through X-ray photoelectron spectroscopy, showing a type-Ⅱ band alignment. Compared to its Schottky barrier diode (SBD) counterpart, the HJD presents a comparable specific ON-resistances (Ron,sp) of 2.8 mΩ·cm² and lower reverse leakage current (IR), leading to an enhanced reverse blocking characteristics with breakdown voltage (BV) of 1675 V and power figure of merit (PFOM) of 1.0 GW/cm². This demonstrates the high quality of the SnO/β-Ga2O3 heterojunction interface. Silvaco TCAD simulation further reveals that electric field crowding at the edge of anode for the SBD was greatly depressed by the introduction of SnO film, revealing the potential application of SnO/β-Ga2O3 heterojunction in the future β-Ga2O3-based power devices.
1. Introduction
Beta-gallium oxide (β-Ga2O3), an ultrawide bandgap semiconductor, has become a prominent candidate for high-voltage and high-power applications due to its outstanding intrinsic properties in comparison to its SiC and GaN counterparts, including an ultrawideband of ~4.8 eV and a theoretical critical electric field up to 8 MV/cm[1]. Advances in synthesis of single-crystal β-Ga2O3 substrates, especially through the cost-competitive melt growth method, also benefit the development of Ga2O3-based vertical high-voltage power devices[2, 3]. A conventional vertical-structured Schottky barrier diode (SBD) based on β-Ga2O3 was fabricated with the anode and cathode metals forming Schottky and Ohmic contacts, respectively. Abundant strategies, including field plate, trench metal−oxide−semiconductor (MOS), mesa termination and implanted high-resistance edge termination techniques[4−8], have been proposed to approach the theoretical limit of β-Ga2O3 SBD. However, under high electric field, a significant increase in leakage current is observed at the metal/Schottky interface, which may be attributed to the combined effects of barrier lowering and enhanced tunneling phenomena[9, 10].
Junction engineering is expected to effectively lower the reverse leakage current and achieve high-performance β-Ga2O3 rectifiers. Limited by the deficiency of p-type epitaxy and p-type ion implantation, the development of p-type Ga2O3 remains challenging. Therefore, exploring alternative p-type materials to form heterojunctions with β-Ga2O3 is a promising approach. In this work, we report the fabrication and characterization of a vertical SnO/β-Ga2O3 heterojunction diode, demonstrating its potential for power device applications.
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Xia Wu, Chenyang Huang, Xiuxing Xu, Jun Wang, Xinwang Yao, Yanfang Liu, Xiujuan Wang, Chunyan Wu, Linbao Luo (2025). Band alignment of SnO/β-Ga2O3 heterojunction and its electrical properties for power device application. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25020008
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Frequently Asked Questions
What is the band alignment of the SnO/β-Ga2O3 heterojunction?
The SnO/β-Ga2O3 heterojunction exhibits a type-II band alignment with valence and conduction band offsets of 2.65 eV and 0.75 eV, respectively.
How does the SnO/β-Ga2O3 heterojunction diode compare to a Schottky barrier diode?
The heterojunction diode shows comparable specific on-resistance (2.8 mΩ·cm²) but lower reverse leakage current, leading to a higher breakdown voltage of 1675 V and a power figure of merit of 1.0 GW/cm².
What fabrication method was used to deposit the SnO film?
The SnO film was deposited using radio frequency (RF) reactive magnetron sputtering.
What is the significance of the TCAD simulation in this study?
The TCAD simulation revealed that the SnO film effectively depresses electric field crowding at the anode edge, which is beneficial for improving the breakdown characteristics of the device.
What are the potential applications of the SnO/β-Ga2O3 heterojunction?
The SnO/β-Ga2O3 heterojunction shows promise for future β-Ga2O3-based power devices, particularly in high-voltage and high-power applications.
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