Non-polar GaN Substrate with Air Gaps for Defect Reduction
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Solution Overview
Problem
The growth of gallium nitride semiconductor thin films often results in crystal defects and polarization effects, leading to reduced recombination efficiency in light emitting diodes due to internal fields and lattice mismatches, which complicates the manufacturing process and limits light extraction efficiency.
Innovation Solution
A non-polar hetero substrate is developed with a defect reduction layer featuring air gaps, allowing for improved surface evenness and light extraction by growing nitride semiconductor layers in a horizontal direction, reducing defects and enhancing light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gallium nitride semiconductor thin films are grown in c-surface crystal direction, then high-quality thin films with little defects can be obtained, but strong internal field and polarization phenomenon occur leading to reduced recombination efficiency
Solution Approach 1:
The patent changes the crystal orientation parameter from c-axis to a-axis by growing the gallium nitride layer on an aluminum nitride substrate with a-plane orientation. This parameter change eliminates the polarization effect while maintaining high film quality, as the a-axis growth direction does not produce the strong internal field associated with c-axis growth.
Solution Approach 2:
Instead of accepting the conventional c-axis growth direction that produces polarization, the patent inverts the approach by using a-axis growth. This inversion of the growth direction fundamentally changes the crystal structure properties, eliminating the harmful polarization effect while achieving high-quality thin films.
2Productivity
If hetero-thin films are grown on conventional substrates, then light emitting diodes can be manufactured, but crystal defects occur and light extraction efficiency is limited
Solution Approach 1:
The patent introduces an aluminum nitride intermediate layer between the sapphire substrate and the gallium nitride active layer. This intermediary layer serves as a buffer that reduces lattice mismatch and thermal expansion differences, thereby reducing crystal defects while enabling successful manufacturing of light emitting diodes.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: sapphire substrate, aluminum nitride buffer layer, and gallium nitride active layer. Each layer is selected for its specific properties, creating a composite material system that minimizes defects and enables high-quality light emitting diode manufacturing.
3Ease of manufacture
If conventional substrate structures are used, then manufacturing process is established, but separation and removal of device structure is difficult and process cost increases
Solution Approach 1:
The patent extracts the gallium nitride device structure from the sapphire substrate by utilizing the aluminum nitride buffer layer as a release interface. This extraction is facilitated by the lattice mismatch between AlN and sapphire, which creates a natural separation plane, allowing easy removal of the device structure after manufacturing.
Solution Approach 2:
The patent segments the overall structure into distinct functional layers: sapphire substrate for initial growth, aluminum nitride buffer layer for defect reduction and release, and gallium nitride active layer for light emission. This segmentation enables independent optimization of each layer and simplifies the separation process.
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 non-polar hetero substrate significantly reduces crystal defects, improves light extraction efficiency, and simplifies the manufacturing process by facilitating easier separation and reducing process costs, resulting in enhanced performance of nitride-based light emitting devices.
Implementation Method 1
a defect reduction layer disposed on the nitride base layer, the defect reduction layer including a plurality of air gaps
Implementation Method 2
inserting an air gap with a predetermined shape and size, a method for manufacturing the same, and a nitride-based light emitting device using the same
Data Source
AI summary
Disclosed are a non-polar hetero substrate, a method for manufacturing the same, and a nitride-based light emitting device using the same. The non-polar hetero substrate includes a non-polar base substrate, a nitride base layer disposed on the substrate, a defect reduction layer disposed on the nitride base layer, the defect reduction layer including a plurality of air gaps, and a nitride semiconductor layer disposed on the defect reduction layer.