Group III Nitride Substrate Blue Shift Suppression
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Solution Overview
Problem
Existing methods for manufacturing nitride semiconductor substrates, particularly gallium-nitride (GaN) substrates, face challenges in achieving smooth surface roughness and reducing process-induced distortions, which affect the crystal quality and performance of epitaxially grown semiconductor layers, leading to issues with blue shift in emission and reduced emission intensity in light emitting devices.
Innovation Solution
A group III nitride crystal substrate with a specific plane orientation inclined between 10° and 80° relative to (0001) planes, characterized by controlled uniform and irregular distortions, and surface roughness, is developed using X-ray diffraction measurements to optimize the substrate's crystallinity and surface quality for epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical polishing is performed on GaN crystal substrate, then surface smoothness is improved, but process-induced degradation layer is formed and surface distortion increases
Solution Approach 1:
The patent extracts and removes the process-induced degradation layer through chemical etching after mechanical polishing, separating the smoothing function from the degradation-causing function. This allows the substrate to have both smooth surface and reduced degradation by removing the harmful layer formed during polishing.
Solution Approach 2:
The patent introduces chemical etching as an intermediary process between mechanical polishing and epitaxial growth. This intermediary step removes the degradation layer created by mechanical polishing, acting as a mediator that eliminates the harmful effects while preserving the surface smoothness benefits.
2Manufacturing precision
If CMP processing is performed on nitride semiconductor substrate, then surface layer removal is achieved, but processing rate is low and cost increases
Solution Approach 1:
The patent combines mechanical polishing and chemical etching into a unified surface preparation process. The mechanical polishing provides initial smoothness while the chemical etching removes degradation, achieving high surface quality without relying solely on slow CMP processing, thereby improving productivity.
Solution Approach 2:
The patent replaces part of the mechanical CMP process with chemical etching. Instead of relying entirely on mechanical removal, the chemical process selectively removes degradation layers, achieving similar or better surface quality at higher processing rates and lower cost.
3Productivity
If epitaxial growth is performed on substrate with poor surface quality, then semiconductor layer is formed, but crystal quality and emission performance deteriorate
Solution Approach 1:
The patent performs preliminary surface preparation including mechanical polishing and chemical etching before epitaxial growth. This preliminary action of removing degradation layers and smoothing the surface ensures high crystal quality in the epitaxial layer, preventing performance deterioration while maintaining productivity.
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 approach results in a substrate that suppresses blue shift in emission and enhances emission intensity by improving the crystallinity and reducing dislocation density, leading to improved performance in light emitting devices with peak wavelengths between 430 nm and 550 nm.
Implementation Method 1
a plane spacing of arbitrary specific parallel crystal lattice planes of the crystal substrate being obtained from X-ray diffraction measurement performed with variation of X-ray penetration depth from a main surface of the crystal substrate
Implementation Method 2
X-ray diffraction measurement performed with variation of X-ray penetration depth
Data Source
AI summary
A group III nitride crystal substrate is provided in which a uniform distortion at a surface layer of the crystal substrate represented by a value of |d1−d2|/d2 obtained from a plane spacing d1 at the X-ray penetration depth of 0.3 μm and a plane spacing d2 at the X-ray penetration depth of 5 μm is equal to or lower than 1.9×10−3, and the main surface has a plane orientation inclined in the <10-10> direction at an angle equal to or greater than 10° and equal to or smaller than 80° with respect to one of (0001) and (000-1) planes of the crystal substrate. A group III nitride crystal substrate suitable for manufacturing a light emitting device with a blue shift of an emission suppressed, an epilayer-containing group III nitride crystal substrate, a semiconductor device and a method of manufacturing the same can thereby be provided.