Performance Analysis of GaN Capping Layer Thickness on GaN/AlGaN/GaN High Electron Mobility Transistors

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• AlGaN/GaN heterostructures are crucial for high-frequency and high-power electronic devices.
• The two-dimensional electron gas (2DEG) at the AlGaN/GaN interface is key to device performance.
• Optimizing layer thicknesses is essential for enhancing device characteristics.

Purpose of the Study:

• To investigate the impact of GaN capping layer and AlGaN layer thickness on 2D electron mobility and carrier concentration.
• To analyze the relationship between layer thickness and device performance metrics like drain current and gate leakage.
• To provide insights for the design of advanced AlGaN/GaN based electronic devices.

Main Methods:

• Fabrication of Al0.25Ga0.75N/GaN and GaN/Al0.25Ga0.75N/GaN heterostructures on sapphire substrates.
• Systematic variation of GaN capping layer thickness (1 nm to 100 nm) and AlGaN layer thickness (5 nm to 30 nm).
• Electrical characterization to measure 2D electron mobility, carrier concentration, drain current, and gate leakage.

Main Results:

• Increasing GaN capping layer thickness enhances electron concentration and drain current, saturating above 40 nm.
• 2D electron mobility decreases monotonically with GaN capping layer thickness, saturating around 830 cm²/Vs.
• AlGaN layer thickness influences carrier concentration with a non-monotonic trend; electron mobility decreases monotonically with increasing AlGaN thickness, reaching 1354 cm²/Vs at 5 nm.

Conclusions:

• GaN capping layer thickness significantly impacts electron concentration and mobility, with an optimal range for device performance.
• AlGaN layer thickness also plays a critical role, affecting carrier concentration and electron mobility.
• The findings offer valuable guidance for optimizing AlGaN/GaN heterostructures for high-performance electronic applications.