Vertical GaN Device with Low-Defect Substrate
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Solution Overview
Problem
Current GaN-based electronic devices face limitations due to high dislocation densities and defects in heteroepitaxial growth, restricting their application to horizontal configurations and preventing the development of high-power vertical devices with low-cost, low-defect substrates.
Innovation Solution
A vertical-type electronic device is developed using a GaN substrate with high electron concentration and low dislocation density, featuring a drift layer with controlled electron concentration and carbon impurity levels, and contact pads formed without hydrogen-containing sources to minimize defects and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heteroepitaxial growth is used to fabricate GaN-based devices, then device fabrication is enabled, but high dislocation densities and defects occur
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the substrate and the GaN drift layer. This buffer layer serves as a transition zone that reduces the lattice mismatch and thermal expansion coefficient difference between the substrate and GaN, thereby significantly reducing dislocation density and defects in the final device structure
Solution Approach 2:
The patent employs ion implantation to precisely control the doping concentration and electrical properties of the drift layer. By changing the doping parameters through ion implantation, the device achieves optimal electrical characteristics with reduced defects and improved performance
2Ease of manufacture
If heteroepitaxial growth is used, then device fabrication is possible, but high defect levels restrict devices to horizontal configurations
Solution Approach 1:
The patent utilizes ion implantation (a form of particle beam processing) to modify the electrical properties of the drift layer. This technique enables precise control of carrier concentration and electrical characteristics, allowing the device to achieve normally-off operation and enabling vertical configuration with improved adaptability
Solution Approach 2:
By changing the doping parameters through ion implantation, the device transitions from horizontal to vertical configuration capability. The controlled doping profiles enable the drift layer to support vertical current flow with appropriate electrical properties, expanding device configuration versatility
3Ease of operation
If conventional contact pad formation is used, then device assembly is simplified, but hydrogen-containing sources increase leakage current
Solution Approach 1:
The patent removes hydrogen-containing sources from the contact pad formation process. By eliminating these harmful elements during fabrication, the device achieves lower leakage current and improved reliability without compromising assembly simplicity
Solution Approach 2:
The patent employs ion implantation in a controlled environment to form contact pads without introducing hydrogen. This inert fabrication approach prevents contamination and ensures low leakage current while maintaining ease of device assembly
4Power
If vertical device configuration is implemented, then high-power capability is achieved, but low-defect substrates are required
Solution Approach 1:
The buffer layer acts as a mediator that decouples the substrate quality requirements from the vertical device performance. It absorbs and mitigates the effects of substrate defects, enabling high-power vertical devices to be fabricated on substrates with moderate quality while maintaining low defect levels in the active regions
Solution Approach 2:
Through ion implantation, the patent precisely controls the electrical parameters of the drift layer to compensate for substrate defects. By optimizing doping profiles and carrier concentrations, the device achieves high-power capability with reduced sensitivity to substrate quality variations
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 solution enables the creation of high-power, low-series resistance, and high-breakdown voltage vertical devices with normally-off operation, overcoming the limitations of horizontal configurations and achieving efficient current flow and high-power switching.
Implementation Method 1
a depletion region in the drift layer created by the p-type contact pad prevents current flow from the n-type contact pad on the drift layer to the drain when no voltage is applied between the n-type contact pad and the p-type contact pad
Data Source
AI summary
The present invention discloses an electronic device formed of a group III nitride. In one embodiment, a substrate is fabricated by the ammonothermal method and a drift layer is fabricated by hydride vapor phase epitaxy. After etching a trench, p-type contact pads are made by pulsed laser deposition followed by n-type contact pads by pulsed laser deposition. The bandgap of the p-type contact pad is designed larger than that of the drift layer. Upon forward bias between p-type contact pads (gate) and n-type contact pads (source), holes and electrons are injected into the drift layer from the p-type contact pads and n-type contact pads. Injected electrons drift to the backside of the substrate (drain).