4.11 A/1650 V Sapphire-Substrate GaN MIS-HEMTs with Thin Buffer for Medium-Voltage Power Applications

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Physics

Background:

• Silicon (Si)-based Gallium Nitride (GaN) power devices require thick buffer layers due to Si's lower breakdown electric field, increasing costs.
• Sapphire substrates offer high electrical insulation and mechanical strength, presenting a viable alternative for GaN power devices.

Purpose of the Study:

• To demonstrate a CMOS-compatible process for GaN Metal-Insulator-Semiconductor High-Electron-Mobility Transistors (MIS-HEMTs) on sapphire substrates using a thin buffer layer.
• To evaluate the performance and reliability of these sapphire-based GaN MIS-HEMTs for medium-voltage applications.

Main Methods:

• Fabrication of GaN MIS-HEMTs on sapphire substrates utilizing a thin buffer layer.
• Characterization of off-state breakdown voltage, on-state current, threshold voltage (VTH), and on-resistance (RON).
• Statistical analysis of device parameters and evaluation of dynamic RON, leakage current, and high-temperature reverse bias (HTRB) reliability.

Main Results:

• Achieved off-state breakdown voltage >1650 V and maximum on-state current > 4.1 A for devices with WG = 20.4 mm and LGD = 24 μm.
• Demonstrated tight statistical distributions of VTH and RON across the wafer.
• Confirmed operational viability at high temperatures (150 °C) and validated long-term reliability for 650 V operation via HTRB tests.

Conclusions:

• Sapphire-based GaN MIS-HEMTs with thin buffer layers offer a cost-effective solution for medium-voltage power applications.
• The fabricated devices exhibit excellent high-voltage performance, good uniformity, and robust reliability at elevated temperatures.