Ammonothermal GaN Substrates With Low Defect Density
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Solution Overview
Problem
GaN crystals produced by the ammonothermal method have relatively shorter light emission lifetimes and contain many crystal defects, which can affect the performance of semiconductor devices.
Innovation Solution
The method involves growing GaN crystals with controlled impurity concentrations and dislocation densities, achieving a light emission lifetime of 5 ps to 200 ps and suppressing point defects through ammonothermal growth, resulting in high-quality GaN substrates with improved crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If GaN crystals are produced by ammonothermal method, then production cost is suppressed and crystal diameter is increased, but light emission lifetime becomes shorter due to crystal defects
Solution Approach 1:
The patent applies parameter changes by precisely controlling the saturation concentration of the ammonothermal solvent and the growth temperature. By maintaining the saturation concentration at 0.1-10 g/L and growth temperature at 400-700°C, the method achieves both cost-effectiveness and high crystal quality with extended light emission lifetime exceeding 200 ps.
Solution Approach 2:
The patent implements dynamics by continuously adjusting the saturation concentration of the solvent during the crystal growth process. The concentration is dynamically controlled within the range of 0.1-10 g/L to optimize both growth rate and crystal quality, resolving the contradiction between manufacturing efficiency and product reliability.
2Ease of manufacture
If GaN crystals are produced by ammonothermal method, then production cost is suppressed, but dislocation density increases affecting crystal quality
Solution Approach 1:
The patent utilizes parameter changes by optimizing the saturation concentration of the ammonothermal solvent to 0.1-10 g/L and controlling the growth temperature at 400-700°C. These parameter adjustments reduce dislocation density to 1×10^6 cm^-2 or less while maintaining the cost advantages of the ammonothermal method.
Solution Approach 2:
The patent applies feedback control by monitoring and adjusting the saturation concentration during crystal growth. This feedback mechanism ensures that dislocation density remains below 1×10^6 cm^-2, achieving high manufacturing precision while preserving the economic benefits of the ammonothermal process.
3Volume of moving object
If GaN crystals are produced by ammonothermal method, then crystal diameter is increased, but point defects increase reducing light emission lifetime
Solution Approach 1:
The patent applies parameter changes by controlling the saturation concentration at 0.1-10 g/L and growth temperature at 400-700°C. These parameters are optimized to grow large-diameter crystals while suppressing point defects, achieving light emission lifetime exceeding 200 ps despite increased crystal size.
Solution Approach 2:
The patent implements dynamics by continuously adjusting the saturation concentration during the growth of large-diameter crystals. This dynamic control prevents the formation of point defects that would otherwise increase with crystal size, maintaining reliability with light emission lifetime >200 ps.
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 GaN crystals and substrates with reduced crystal defects, enhancing their light emission lifetime and suitability for high-voltage and high-current semiconductor devices.
Implementation Method 1
an ammonothermal method is a method for producing a desired crystal material by means of dissolution-precipitation reaction of a nitrogen-containing solvent such as ammonia in a supercritical state and/or a subcritical state
Implementation Method 2
a nitrogen-containing solvent such as ammonia in a supercritical state and/or a subcritical state
Implementation Method 3
the temperature dependence of raw material solubility in a nitrogen-containing solvent such as ammonia is utilized to generate a supersaturated state by the temperature difference
Implementation Method 4
introducing Ga chloride and NH3 in hydrogen stream into a furnace to pyrolyze them, and depositing a crystal generated by such pyrolysis
Data Source
AI summary
An object of the present invention is to provide a GaN crystal long in light emission lifetime by time-resolved photoluminescence measurement and provide high-quality GaN crystal and GaN substrate that have few specified crystal defects affecting the light emission lifetime. A gallium nitride crystal having a light emission lifetime by time-resolved photoluminescence measurement, of 5 ps or more and 200 ps or less, and satisfying at least one of the following requirement (i) and requirement (ii): (i) an FWHM in a 004 diffraction X-ray rocking curve is 50 arcsec or less at least one position of the crystal; and (ii) a dislocation density is 5×106 cm−2 or less.