Carbon-Doped GaN Substrate Structure for Higher Crystallinity
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Solution Overview
Problem
Thickening GaN epitaxial layers improves crystallinity but requires complex buffer layers, increases growth time and raw material costs, and makes substrates susceptible to cracks and plastic deformation.
Innovation Solution
A nitride semiconductor substrate with a stress-relaxing layer and a carbon-doped GaN layer, where the GaN layer comprises high carbon concentration layers and a low carbon concentration layer sandwiched between them, reducing dislocations and improving crystallinity without increasing the GaN layer thickness or using special raw materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the GaN epitaxial layer thickness is increased to improve crystallinity, then the crystallinity is improved, but the growth time increases and raw material costs increase
Solution Approach 1:
The patent applies local quality by creating a carbon concentration gradient within the GaN layer. The carbon concentration is higher at the lower portion (near the buffer layer) and lower at the upper portion, allowing different regions to serve different functions: the high-carbon region suppresses dislocation generation while the low-carbon region maintains good crystallinity, eliminating the need for thick uniform layers
Solution Approach 2:
The patent changes the carbon concentration parameter throughout the GaN layer thickness. By controlling carbon concentration to be higher at the lower portion and lower at the upper portion, the patent achieves both dislocation suppression and good crystallinity without increasing overall layer thickness or growth time
2Manufacturing precision
If the GaN epitaxial layer thickness is increased to improve crystallinity, then the crystallinity is improved, but the substrate becomes susceptible to cracks and plastic deformation
Solution Approach 1:
The patent uses local quality by concentrating carbon doping in the lower portion of the GaN layer where dislocation generation occurs. This localized approach suppresses dislocations without requiring thick uniform layers that would induce substrate stress, cracks, and plastic deformation
Solution Approach 2:
By changing the carbon concentration parameter to be higher at the lower portion and lower at the upper portion, the patent achieves dislocation suppression with thin layers, avoiding substrate damage associated with thick epitaxial layers
3Manufacturing precision
If SiN intermediate layers are inserted to stop dislocations and improve crystallinity, then the crystallinity is improved, but special raw materials such as monosilane are required and formation time increases
Solution Approach 1:
The patent changes the carbon concentration parameter within the GaN layer itself to suppress dislocations, eliminating the need for SiN intermediate layers and special raw materials like monosilane. This is achieved by controlling carbon concentration to be higher at the lower portion where dislocation generation occurs
Solution Approach 2:
The patent extracts the dislocation suppression function from separate SiN intermediate layers and integrates it into the GaN layer itself through carbon concentration control, simplifying the structure and eliminating special raw material requirements
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 substrate achieves improved crystallinity and breakdown voltage characteristics without thickening the GaN layer or using special raw materials, reducing production costs and preventing issues like cracks and deformation.
Implementation Method 1
a dislocation can be reduced at the low carbon concentration layer while securing a breakdown voltage with the high carbon concentration layer in the GaN layer
Implementation Method 2
securing a breakdown voltage with the high carbon concentration layer in the GaN layer
Data Source
AI summary
The present invention is a nitride semiconductor substrate including a nitride semiconductor thin film formed on a substrate, in which the nitride semiconductor thin film includes a stress-relaxing layer formed on the substrate and a carbon-doped GaN layer formed on the stress-relaxing layer, and the GaN layer includes high carbon concentration layers and a low carbon concentration layer, the low carbon concentration layer being sandwiched between the high carbon concentration layers and having a lower carbon concentration by 75% or more than the high carbon concentration layers. This provides the nitride semiconductor substrate with improved crystallinity without increasing a thickness of a GaN epitaxial layer and without using other special materials, and a method for producing the substrate.