Key Takeaways & Executive Findings
- •• The trenched n+-GaN cap layer doubles the 2DEG density, reducing specific ON-resistance to ~2.4 mΩ·cm². • The Si3N4 passivation layer suppresses surface defects from dry etching, reducing leakage current to ~8×10⁻⁵ A·cm⁻² and achieving a breakdown voltage of 876 V. • The proposed structure achieves a Baliga's figure of merit (BFOM) of ~319 MW·cm⁻², a significant improvement. • The Si3N4 layer also suppresses electron capture and transport, improving dynamic ON-resistance characteristics.
Abstract
In this work, we design and fabricate AlGaN/GaN-based Schottky barrier diodes (SBDs) on a silicon substrate with a trenched n+-GaN cap layer. With the developed physical models, we find that the n+-GaN cap layer provides more electrons into the AlGaN/GaN channel, which is further confirmed experimentally. When compared with the reference device, this increases the two-dimensional electron gas (2DEG) density by two times and leads to a reduced specific ON-resistance (Ron,sp) of ~2.4 mΩ·cm2. We also adopt the trenched n+-GaN structure such that partial of the n+-GaN is removed by using dry etching process to eliminate the surface electrical conduction when the device is set in the off-state. To suppress the surface defects that are caused by the dry etching process, we also deposit Si3N4 layer prior to the deposition of field plate (FP), and we obtain a reduced leakage current of ~8 × 10−5 A·cm−2 and breakdown voltage (BV) of 876 V. The Baliga’s figure of merit (BFOM) for the proposed structure is increased to ~319 MW·cm−2. Our investigations also find that the pre-deposited Si3N4 layer helps suppress the electron capture and transport processes, which enables the reduced dynamic Ron,sp.
1. Introduction
Gallium nitride (GaN) material has gathered significant research attention due to its outstanding material properties, including a large bandgap of ~3.4 eV, high critical breakdown electric field of ~3.3 MV/cm, and thermal conductivity of ~2 W/cm·K. Because of the low cost, large GaN-on-silicon wafer size and compatibility with CMOS fabrication processes, GaN power devices grown on silicon substrate have emerged as a promising candidate among the power device community. The unique material property of the high-mobility and the high-density two-dimensional electron gas (2DEG) at the AlGaN/GaN heterojunction enables low specific on-resistance and high switching frequency, making them suitable for power electronics applications.
However, the performance of AlGaN/GaN Schottky barrier diodes (SBDs) is often limited by trade-offs between breakdown voltage (BV) and specific on-resistance (Ron,sp). To improve the Baliga's figure of merit (BFOM), various techniques have been proposed, such as field plates, recessed anodes, and surface passivation. In this work, we introduce a trenched n+-GaN cap layer and a local Si3N4 passivation layer to enhance the 2DEG density and suppress surface-related issues, thereby improving both static and dynamic performance.
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Zhizhong Wang, Jingting He, Fuping Huang, Xuchen Gao, Kangkai Tian, Chunshuang Chu, Yonghui Zhang, Shuting Cai, Xiaojuan Sun, Dabing Li, Xiao Wei Sun, Zi-Hui Zhang (2025). AlGaN/GaN-based SBDs grown on silicon substrates with trenched n+-GaN cap layer and local passivation layer to improve BFOM and dynamic properties. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25010024
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Frequently Asked Questions
What is the main innovation of this paper?
The paper introduces a trenched n+-GaN cap layer and a local Si3N4 passivation layer in AlGaN/GaN SBDs on silicon substrates, which significantly increases 2DEG density, reduces specific on-resistance, and improves breakdown voltage and dynamic performance.
How does the n+-GaN cap layer improve device performance?
The n+-GaN cap layer provides additional electrons to the AlGaN/GaN channel, doubling the 2DEG density, which reduces the specific on-resistance to ~2.4 mΩ·cm².
What role does the Si3N4 layer play?
The Si3N4 layer suppresses surface defects caused by dry etching, reducing leakage current to ~8×10⁻⁵ A·cm⁻² and enhancing breakdown voltage to 876 V. It also suppresses electron capture and transport, improving dynamic on-resistance.
What is the achieved Baliga's figure of merit (BFOM)?
The proposed structure achieves a BFOM of ~319 MW·cm⁻², which is a significant improvement over conventional devices.
What are the potential applications of this technology?
The improved AlGaN/GaN SBDs are suitable for high-efficiency power electronics, such as power supplies, inverters, and electric vehicle chargers, where low loss and high breakdown voltage are critical.
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