Group III Nitride Semiconductor Mesa Angle Optimization
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Solution Overview
Problem
Existing methods for growing Group III nitride semiconductor crystals on mesa-formed substrates face challenges such as deteriorated crystallinity and flatness due to void formation on side surfaces, uneven threading dislocation density, and complexity in changing growth conditions to bury steps, leading to suboptimal semiconductor performance.
Innovation Solution
The method involves forming mesas on a substrate with side surfaces oriented so that the most parallel low-index plane is a m-plane (1-100) and the angle between the lateral vector and the projected normal vector of the m-plane is between 0.5° and 6°, allowing for both vertical and lateral growth under consistent conditions, thereby reducing threading dislocation density and achieving uniformity on the semiconductor surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Group III nitride semiconductor is grown on mesa-formed sapphire substrate using conventional methods, then light extraction performance is improved, but voids are formed on side surfaces of the dents or mesas, resulting in deteriorated crystallinity and flatness
Solution Approach 1:
The patent applies asymmetry by orienting the side surfaces of mesas and dents at specific asymmetric angles relative to the a-plane of the sapphire substrate. The side surfaces are inclined at angles of 15°-30° from the a-plane, creating an asymmetric configuration that prevents void formation while maintaining light extraction performance. This asymmetric orientation ensures that GaN grows preferentially on top surfaces and bottom surfaces rather than side surfaces, eliminating the void formation problem.
2Manufacturing precision
If the sides in planar view of dents or mesas intersect with an a-plane of the sapphire substrate, then GaN is difficult to grow on side surfaces and superior crystallinity is obtained, but lateral growth of GaN is slow and surface flatness is deteriorated
Solution Approach 1:
The patent applies parameter changes by precisely controlling the inclination angle of side surfaces relative to the a-plane. Instead of using exact 15° or 30° angles, the patent specifies a range of 15°-30° from the a-plane, which optimizes both crystallinity and surface flatness. This parameter optimization allows sufficient lateral growth to bury steps while maintaining the crystallinity benefits of a-plane intersection.
3Manufacturing precision
If steps are buried by laterally growing Group III nitride semiconductor, then good crystallinity is achieved, but growth conditions must be changed from vertical to lateral growth, complicating the production method
Solution Approach 1:
The patent applies preliminary action by pre-configuring the side surfaces of mesas and dents at specific angles (15°-30° from the a-plane) before growth begins. This preliminary geometric configuration enables subsequent vertical growth to automatically achieve both step burial and good crystallinity without requiring a separate lateral growth step. The pre-set angle ensures that vertical growth inherently produces the desired lateral coverage, simplifying the production method.
4Reliability
If hexagonal prism mesas are used with sides at 15° to the m-axis, then crystal growth inhibition is achieved, but the angle specification limits adaptability to different growth conditions and requirements
Solution Approach 1:
The patent applies parameter changes by expanding the acceptable angle range from a fixed 15° to a range of 15°-30° from the a-plane. This broader parameter range provides flexibility to adapt to different growth conditions, equipment variations, and product requirements while maintaining reliable crystal growth control. The range allows optimization for specific applications without sacrificing the fundamental growth inhibition benefit.
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 results in improved crystallinity, reduced threading dislocation density, and uniform surface quality of the Group III nitride semiconductor, enhancing the production efficiency and yield of light-emitting devices by burying steps without altering growth conditions.
Implementation Method 1
growing Group III nitride semiconductor in a c-axis direction of Group III nitride semiconductor on the top surfaces of the mesas and the bottom surfaces of the dents
Data Source
AI summary
A method for producing a Group III nitride semiconductor comprising forming mesas on a main surface of a substrate, and growing Group III nitride semiconductor in a c-axis direction thereof, wherein the plane most parallel to the side surfaces of the mesas or the dents among the low-index planes of growing Group III nitride semiconductor is a m-plane (1-100), and when a projected vector obtained by orthogonally projecting a normal vector of the processed side surface to the main surface is defined as a lateral vector, an angle between the lateral vector and a projected vector obtained by orthogonally projecting a normal vector of the m-plane of the growing Group III nitride semiconductor to the main surface is 0.5° or more and 6° or less.