Nitride Semiconductor Defect Reduction via Plasma Treatment
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Solution Overview
Problem
Nitride-based semiconductor devices, such as GaN-based LEDs, face challenges in achieving high luminous efficiency due to crystal defects and total internal reflection caused by lattice mismatch between the sapphire substrate and GaN-based materials, leading to reduced internal quantum efficiency and light extraction efficiency.
Innovation Solution
A method involving a patterned substrate with plasma etching treatment to remove surface and crystal defects, followed by the formation of an aluminum nitride-based film using physical vapor deposition and a nitride-based semiconductor stacked structure via metal organic chemical-vapor deposition, to minimize defects and enhance epitaxial growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dry etching is used to form protrusions on the sapphire substrate, then light scattering is improved, but surface defects are generated on the side walls of protrusions
Solution Approach 1:
The patent applies preliminary plasma treatment to the sapphire substrate before epitaxial growth to remove surface defects and contaminants from the patterned surface. This preliminary cleaning action prevents defect formation during subsequent GaN crystal growth, resolving the contradiction by addressing the harmful surface defects created by dry etching before they can propagate into the epitaxial layer.
2Reliability
If physical vapor deposition is used to form aluminum nitride buffer layer, then crystal quality is improved, but crystal defects are formed on the side face of protrusions
Solution Approach 1:
The patent introduces plasma treatment as an intermediary process between physical vapor deposition of the AlN buffer layer and subsequent epitaxial growth. This plasma intermediary step removes the crystal defects formed on the protrusion side faces during PVD, preventing them from propagating into the GaN epitaxial structure while preserving the beneficial crystal quality improvement from the buffer layer.
3Reliability
If patterned substrate is used to control nucleation islands, then GaN crystal quality is improved, but total internal reflection is increased due to high refractive index
Solution Approach 1:
The patent applies local quality modification by creating patterned protrusions with specific geometric characteristics on the sapphire substrate. The patterned structure provides localized nucleation sites that improve GaN crystal quality while the specific geometry and distribution of protrusions optimize light extraction through controlled scattering, addressing both crystal quality and light extraction efficiency simultaneously.
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 method significantly reduces crystal defects, improving the luminous efficiency of nitride-based semiconductor devices by up to 5% compared to conventional methods, by minimizing light absorption and enhancing light extraction.
Implementation Method 1
plasma etching treatment to remove crystal defects
Implementation Method 2
in the dry etching, a substrate 10 is etched using physical bombardment
Implementation Method 3
forming an aluminum nitride-based film using physical vapor deposition
Implementation Method 4
formation of a nitride-based semiconductor stacked structure via metal organic chemical-vapor deposition
Implementation Method 5
effectively scattering light emitted from the active region to suppress total internal reflection
Implementation Method 6
since the GaN-based materials have a high refractive index, light emitted from the active region of LED would be totally internally reflected
Data Source
AI summary
A nitride-based semiconductor device includes a patterned substrate having an etched surface that is formed with a plurality of protrusions, an aluminum nitride (AlN)-based film disposed on the etched surface, and a nitride-based semiconductor stacked structure disposed on the aluminum nitride-based film. Each of the protrusions has a side face. The AlN-based film includes a plurality of crystal defects formed on the side face of each protrusion. Each of the crystal defects has a width of smaller than 20 nm and/or the number of the crystal defects that are formed on the side face of each protrusion and that have a width of greater than 10 nm is less than 10. A method for preparing the semiconductor device is also disclosed.