Nitride Single-Crystal Substrate with Graded Doping for Vertical LEDs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of nitride single crystal substrates for vertical light emitting devices is hindered by lattice defects and cracks due to lattice constant and thermal expansion coefficient mismatches with sapphire substrates, and high impurity doping leads to stress and degradation of crystal quality.
Innovation Solution
A nitride single crystal substrate with an upper region highly doped and a lower region intentionally undoped, grown using Hydride Vapor Phase Epitaxy, ensuring superior crystallinity and conductivity, allowing for efficient manufacturing of vertical nitride light emitting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nitride single crystal substrate is highly doped to be sufficiently conductive, then the conductivity is improved, but the stress and defect density increase leading to degradation of crystal quality
Solution Approach 1:
The patent applies local quality by creating distinct doped and undoped regions within the nitride single crystal substrate. The lower region is intentionally undoped to maintain superior crystallinity and low defect density, while the upper region is highly doped to provide sufficient conductivity for device operation. This spatial differentiation of doping concentrations allows each region to optimize its local properties without compromising the other.
2Ease of manufacture
If the nitride single crystal is grown on a sapphire substrate, then the manufacturing process is simplified, but lattice defects and cracks occur due to lattice constant mismatch and thermal expansion coefficient difference
Solution Approach 1:
The patent segments the nitride single crystal substrate into two functional regions with different doping concentrations. The lower undoped region serves as a high-quality crystal foundation grown on the sapphire substrate, while the upper doped region provides the necessary conductivity. This segmentation allows the substrate to maintain good crystal quality at the interface with the sapphire substrate while still achieving sufficient overall conductivity for device operation.
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 superior crystallinity and simplifies the lapping process, ensuring high-quality vertical light emitting devices with improved conductivity and reduced defect density.
Implementation Method 1
A nitride single crystal substrate with an upper region highly doped and a lower region intentionally undoped, grown using Hydride Vapor Phase Epitaxy
Data Source
AI summary
A nitride semiconductor single crystal substrate, a manufacturing method thereof and a method for manufacturing a vertical nitride semiconductor device using the same. According to an aspect of the invention, in the nitride semiconductor single crystal substrate, upper and lower regions are divided along a thickness direction, the nitride single crystal substrate having a thickness of at least 100 μm. Here, the upper region has a doping concentration that is five times or greater than that of the lower region. Preferably, a top surface of the substrate in the upper region has Ga polarity. Also, according to a specific embodiment of the invention, the lower region is intentionally un-doped and the upper region is n-doped. Preferably, each of the upper and lower regions has a doping concentration substantially identical in a thickness direction.