C-plane GaN substrate with controlled facet growth
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Solution Overview
Problem
The existing methods for producing C-plane GaN substrates result in unstable quality and restricted shape and dimension of nitride semiconductor devices due to uncontrolled pit formation and off-angle variations on the growth surface.
Innovation Solution
A C-plane GaN substrate with a controlled number density of facet growth areas, regular arrangement, and suppressed off-angle variation, grown using a seed with a dot mask pattern, ensuring minimal core presence and high oxygen concentration, which allows for stable and flexible nitride semiconductor device formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pits are generated on the growth surface of GaN by controlling growth conditions, then oxygen can be added to the GaN crystal, but the concentration and distribution of impurities varies between production lots leading to unstable quality
Solution Approach 1:
A dot pattern is formed on the surface of the GaN template with a growth mask before crystal growth begins. This preliminary patterning creates predetermined pit locations that ensure consistent oxygen incorporation across different production lots, resolving the quality stability issue while maintaining adequate oxygen concentration.
Solution Approach 2:
Instead of uniform pit distribution, the invention creates localized pits at specific positions defined by the dot pattern. This local quality approach allows oxygen to be added at controlled locations, ensuring consistent impurity distribution and improving quality stability between production lots.
2Quantity of substance
If a dot pattern is formed on the surface of a GaN template with a growth mask to generate surface pits with cores, then oxygen uptake is improved, but the cores create huge crystal defects that restrict device shape and dimension
Solution Approach 1:
The invention extracts or removes the harmful cores from the growth process by using a dot pattern that generates surface pits without forming cores. The growth mask pattern controls pit formation to occur without the accompanying core defects that would otherwise restrict device shape and dimension.
Solution Approach 2:
The invention converts the potential harm of core formation into a benefit by using the dot pattern to create pits that promote oxygen uptake without generating cores. The controlled pit formation at dot locations achieves the desired oxygen concentration while maintaining crystal quality suitable for various device configurations.
3Quantity of substance
If pits are generated on the growth surface without controlling their positions, then oxygen can be incorporated into the crystal, but the uncontrolled distribution leads to variation in impurity concentration between production lots
Solution Approach 1:
The dot pattern is formed on the GaN template surface before crystal growth, preliminarily determining the exact locations where pits will form. This preliminary positioning ensures that oxygen incorporation occurs at consistent locations across all production lots, achieving precise control over impurity distribution.
Solution Approach 2:
The invention changes the parameter of pit position from uncontrolled to controlled by introducing the dot pattern geometry. The dot pattern parameters (spacing, size, arrangement) define the pit locations, transforming the random distribution into a controlled, repeatable pattern that ensures consistent impurity distribution across production lots.
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 solution provides a stable and mildly restrictive C-plane GaN substrate that supports nitride semiconductor devices with controlled shape and dimension, maintaining high quality and reduced off-angle variations, enhancing the reliability of nitride semiconductor devices.
Implementation Method 1
A GaN crystal is grown on the GaN template in the c-axis direction
Implementation Method 2
GaN crystal grown by an HVPE (Hydride Vapor Phase Epitaxy) method
Implementation Method 3
Examples of dopants used for imparting conductivity to a GaN crystal include oxygen (O)
Data Source
AI summary
A C-plane GaN substrate only mildly restricts the shape and dimension of a nitride semiconductor device formed on the substrate. The variation of an off-angle on the main surface of the substrate is suppressed. In the C-plane GaN substrate: the substrate comprises a plurality of facet growth areas each having a closed ring outline-shape on the main surface; the number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm−2 on the main surface; and, when any circular area of 4 cm diameter is selected from an area which is on the main surface and is distant by 5 mm or more from the outer peripheral edge of the substrate, the variation widths of an a-axis direction component and an m-axis direction component of an off-angle within the circular area is each 0.25 degrees or less.