GaN HEMT Buffer Doping Gradient for Current Collapse Control
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Solution Overview
Problem
Existing GaN-based HEMT devices suffer from issues such as current collapse, degraded 2DEG confinement, and high dislocation density due to low-quality carbon-doped GaN buffers, which are caused by low growth temperature, pressure, and high growth rate conditions.
Innovation Solution
Implementing a linear carbon doping gradient in the upper portion of the GaN buffer layer by combining intrinsic and extrinsic carbon doping, using hexene as the extrinsic dopant, to improve the quality of the GaN buffer and enhance 2DEG confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low growth temperature, pressure, and high growth rate conditions are used to form carbon-doped GaN buffer, then the buffer formation speed is improved, but the buffer quality deteriorates causing current collapse and high dislocation density
Solution Approach 1:
The patent applies parameter changes by implementing a linear carbon doping gradient in the GaN buffer layer, where the carbon doping concentration varies continuously from the substrate interface to the channel interface. This gradient structure allows the buffer to maintain high growth rates while improving overall buffer quality by reducing dislocation density and preventing current collapse through optimized carbon distribution throughout the buffer thickness.
Solution Approach 2:
The patent applies local quality by creating different carbon doping concentrations at different depths within the GaN buffer layer. The carbon doping concentration is highest near the substrate interface and progressively decreases toward the channel interface, allowing each region of the buffer to have optimized local properties for its specific function in the device structure.
2Productivity
If low growth temperature and high growth rate are used, then manufacturing efficiency is improved, but dislocation density increases and 2DEG confinement is degraded
Solution Approach 1:
The patent uses parameter changes by implementing a linear carbon doping gradient that compensates for the effects of low growth temperature and high growth rate. The gradient structure reduces dislocation density throughout the buffer, thereby improving 2DEG confinement quality while maintaining high manufacturing efficiency through rapid buffer formation.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the carbon doping gradient in the buffer layer before device operation. This gradient structure is formed during buffer growth to proactively reduce dislocation density and establish proper 2DEG confinement characteristics, preventing quality issues before they affect device performance.
3Ease of manufacture
If uniform carbon doping is applied throughout the GaN buffer, then doping process simplicity is improved, but current collapse effects are not effectively reduced
Solution Approach 1:
The patent applies local quality by transitioning from uniform carbon doping to a linear carbon doping gradient, where the doping concentration varies systematically through the buffer thickness. This gradient structure effectively reduces current collapse effects by optimizing carbon distribution, with higher concentrations near the substrate and lower concentrations near the channel, while remaining implementable through standard doping processes.
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
The carbon doping gradient effectively reduces current collapse effects and dislocation density, improving the performance of GaN-based HEMT devices by compensating electron traps and enhancing gate control.
Implementation Method 1
doping a second thickness of GaN with a second concentration of the dopant such that the second concentration of dopant has a gradient through the second thickness that progressively decreases in a direction away from the first thickness
Data Source
AI summary
A method of manufacturing a High-Electron-Mobility Transistor (HEMT) includes: preparing a substrate; forming a first buffer over the substrate; forming a second buffer over the first buffer, wherein forming the second buffer includes doping a first thickness of a material such as gallium nitride (GaN) with a first concentration of a dopant such as carbon, and doping a second thickness of the material with a second concentration of the dopant such that the second concentration of dopant has a gradient though the second thickness which progressively decreases in a direction away from the first thickness; forming a channel layer such as a GaN channel over the second buffer; forming a barrier layer such as aluminum gallium nitride (AlGaN) over the channel layer; and forming drain, source and gate terminals for the HEMT.