GaN HEMT AlGaN Layer Structure for Low On-Resistance Control
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Solution Overview
Problem
The challenge in semiconductor technology is to reduce the on-resistance of gallium nitride (GaN) high electron mobility transistors (HEMTs) without affecting the threshold voltage, which is crucial for withstanding voltage spikes and minimizing power dissipation in high-power applications.
Innovation Solution
The solution involves forming a second AlGaN layer with a different composition over the AlGaN-GaN heterojunction, using sidewall spacers and selective epitaxy to decouple on-resistance from the threshold voltage, achieved by increasing the aluminum concentration in the AlGaN layer and adjusting its thickness, thereby enhancing spontaneous and piezoelectric polarization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the aluminum concentration in the AlGaN layer is increased to reduce on-resistance, then the threshold voltage decreases, which reduces the device's ability to withstand voltage spikes
Solution Approach 1:
The AlGaN layer is segmented into multiple layers with different aluminum concentrations. The first AlGaN layer has a higher aluminum concentration (0.2-0.35) to reduce on-resistance, while the second AlGaN layer has a lower aluminum concentration (0.1-0.2) to maintain threshold voltage. This segmentation allows independent optimization of on-resistance and threshold voltage, resolving the technical contradiction between energy loss and reliability.
2Loss of energy
If the thickness of the AlGaN layer is increased to enhance polarization effects, then the on-resistance decreases, but the manufacturing complexity increases
Solution Approach 1:
Different regions of the AlGaN structure have different local qualities in terms of aluminum concentration. The first AlGaN layer (30-150 nm thick) has higher aluminum concentration for strong polarization effects and low on-resistance, while the second AlGaN layer (10-50 nm thick) has lower aluminum concentration for threshold voltage control. This local quality differentiation achieves low on-resistance without excessive overall thickness, simplifying manufacturing.
3Productivity
If the device is scaled down to meet higher storage capacity and processing demands, then the manufacturing complexity increases
Solution Approach 1:
The invention optimizes specific parameters of the AlGaN layers (aluminum concentration and thickness) to achieve high performance in scaled devices. By precisely controlling the aluminum concentration gradient and layer thicknesses, the device maintains low on-resistance and appropriate threshold voltage even at scaled dimensions, enabling high productivity without proportionally increasing manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for independent control of on-resistance and threshold voltage, reducing on-resistance to between 0.1 mohm/mm and 0.25 mohm/mm while maintaining a suitable threshold voltage range, enhancing the device's ability to withstand voltage spikes and reduce power dissipation.
Implementation Method 1
forming a first aluminum gallium nitride (AlGaN) layer on the GaN layer; forming a second AlGaN layer over the AlGaN-GaN heterojunction... enhancing spontaneous and piezoelectric polarization effects
Implementation Method 2
enhancing spontaneous and piezoelectric polarization effects
Data Source
AI summary
An efficient AlGaN/GaN High Electron Mobility Transistor (HEMT) device suitable for use in high frequency and high power applications is disclosed. By including a second AlGaN layer that is selectively deposited outside the gate region, it is possible to reduce on-resistance of the device without affecting the threshold voltage. Independent control of Rds-on and threshold voltage Vth can therefore be achieved, resulting in enhanced performance.