Bulk Diffusion Nitride Crystal Growth via Porous Source
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Solution Overview
Problem
Current methods for growing large, high-quality Group III-V nitride crystals, such as AlN and GaN, face challenges due to excessive nucleation sites, uncontrollable crystal orientation, and induced stress, which hinder the production of suitable seed crystals for electronic and piezoelectric devices.
Innovation Solution
A method involving a sublimation and bulk diffusion process using a porous body with a refractory filler, where a temperature gradient is established to diffuse Group III-V species, controlling nucleation and crystal growth, and incorporating materials like Al, Ga, and In to enhance crystal quality and reduce oxygen contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sublimation method is used to grow large AlN crystals, then crystal size can be increased, but induced internal stress increases and crystal quality deteriorates
Solution Approach 1:
The patent employs a porous AlN body as the source material instead of conventional dense sources. The porous structure allows controlled diffusion of Al and N species throughout the body, enabling uniform supply of growth materials and reducing thermal stress concentration. This porous source design facilitates controlled nucleation and growth while minimizing the induced internal stress that plagues conventional sublimation methods.
Solution Approach 2:
The patent modifies the sublimation process parameters by introducing a porous body with controlled porosity and using it as the source material. This changes the mass transport characteristics from conventional surface-sublimation to bulk-diffusion controlled processes, allowing lower growth temperatures and reduced thermal gradients that minimize stress while maintaining large crystal growth.
2Productivity
If high sublimation temperatures are used to achieve viable AlN growth rates, then crystal growth speed increases, but aluminum vapor becomes highly reactive with materials and crystal purity decreases
Solution Approach 1:
The patent changes the temperature parameter by enabling AlN growth at lower temperatures than conventional sublimation. The porous body structure facilitates controlled mass transport, allowing growth rates to be maintained at reduced temperatures where aluminum vapor reactivity is minimized, thus reducing contamination of crucible materials and improving crystal purity.
Solution Approach 2:
The porous AlN body serves as a controlled source that releases Al and N species through diffusion rather than rapid sublimation. This controlled release mechanism allows growth at lower temperatures where material reactivity is reduced, preventing contamination while maintaining adequate growth rates through the extended diffusion pathway.
3Volume of moving object
If thermal grain expiation via bowed thermal fields is used to expand AlN seed crystal size, then crystal size increases, but stress is transferred throughout the bulk and crystal quality deteriorates
Solution Approach 1:
The porous AlN body acts as a stress-distributing source structure. Instead of using sharp thermal gradients that concentrate stress (as in bowed thermal field methods), the porous structure distributes the thermal and mechanical stresses throughout its volume, preventing stress concentration and maintaining crystal quality during growth and expansion.
4Productivity
If extreme temperature gradients are used in closed space sublimation to achieve sufficient Ga flux, then crystal growth speed increases, but crystal quality deteriorates
Solution Approach 1:
The patent changes the mass transport mechanism from surface-sublimation controlled by extreme gradients to bulk-diffusion controlled by the porous structure. This allows Ga flux to be sufficient for good growth rates while the distributed diffusion pathway prevents the formation of extreme temperature gradients that would otherwise degrade crystal quality.
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 enables the production of large, high-quality Group III-V nitride crystals with controllable orientations, reducing stress and improving crystal size and purity, suitable for use as seeds or device substrates.
Implementation Method 1
diffusing at least one of a group-Ill or a nitrogen species through a porous body
Implementation Method 2
a temperature gradient is established to diffuse Group III-V species
Implementation Method 3
sublimation and bulk diffusion process
Data Source
AI summary
The present disclosure generally relates to systems and methods for growing group III-V nitride crystals. In particular the systems and methods include diffusing constituent species of the crystals through a porous body composed of the constituent species, where the species freely nucleate to grow large nitride crystals.