Semipolar GaN Substrate Orientation for Dislocation Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor devices using gallium nitride-based semiconductors face challenges with strain relaxation and dislocation formation due to lattice constant differences between the substrate and the semiconductor layer, particularly on c-plane, a-plane, and m-plane substrates, which degrades crystal quality and increases dislocation density.
Innovation Solution
A group III nitride semiconductor device with a supporting base having a primary surface tilted by an off-angle of 10 to 80 degrees relative to the c-plane, featuring a semiconductor layer with a hexagonal gallium nitride-based semiconductor, such as AlGaN or InGaN, where the tilt angle between the substrate and semiconductor planes ranges from 0.05 to 2 degrees, suppressing strain relaxation and dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gallium nitride-based semiconductor layer is grown on a c-plane, a-plane, or m-plane substrate, then the growth process is straightforward and well-established, but strain relaxation occurs due to lattice constant differences, leading to dislocation formation and degraded crystal quality
Solution Approach 1:
The invention changes the substrate orientation parameter from conventional c-plane, a-plane, or m-plane to a semipolar plane with a specific off-angle range (10-80 degrees from c-plane). This parameter change in substrate orientation fundamentally alters the strain distribution characteristics, allowing strain accommodation without dislocation formation while maintaining high crystal quality
2Reliability
If a large tilt angle is used to utilize semipolarity, then strain relaxation is suppressed and dislocation density is reduced, but the manufacturing complexity and difficulty of achieving precise orientation increase
Solution Approach 1:
The invention identifies and applies a specific range for the off-angle parameter (10-80 degrees from c-plane) that optimizes the balance between strain suppression and manufacturing feasibility. Within this range, the semipolar substrate provides sufficient strain accommodation while remaining workable with existing fabrication capabilities
Solution Approach 2:
The invention uses a GaN buffer layer as an intermediate copying layer between the semipolar substrate and the gallium nitride-based semiconductor layer. This buffer layer copies and adapts the lattice structure, facilitating epitaxial growth while managing the orientation mismatch and reducing the practical difficulty of precise alignment
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
This approach effectively reduces dislocation density and enhances crystal quality, enabling improved emission performance in light-emitting diodes and semiconductor lasers with emission peaks in the 400 to 550 nm range.
Implementation Method 1
the hexagonal gallium nitride-based semiconductor is elastically deformed in the plane that is parallel to the primary surface of the supporting base
Data Source
AI summary
A primary surface 23a of a supporting base 23 of a light-emitting diode 21a tilts by an off-angle of 10 degrees or more and less than 80 degrees from the c-plane. A semiconductor stack 25a includes an active layer having an emission peak in a wavelength range from 400 nm to 550 nm. The tilt angle “A” between the (0001) plane (the reference plane SR3 shown in FIG. 5) of the GaN supporting base and the (0001) plane of a buffer layer 33a is 0.05 degree or more and 2 degrees or less. The tilt angle “B” between the (0001) plane of the GaN supporting base (the reference plane SR4 shown in FIG. 5) and the (0001) plane of a well layer 37a is 0.05 degree or more and 2 degrees or less. The tilt angles “A” and “B” are formed in respective directions opposite to each other with reference to the c-plane of the GaN supporting base.