Single-Crystalline Aluminum Nitride Substrate UV Transparency
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Solution Overview
Problem
Current methods for manufacturing single-crystalline aluminum nitride (AIN) fail to achieve sufficient transparency for ultraviolet light, particularly at 265 nm, due to high absorption rates, which limits their application in UV LED devices and sterilization applications.
Innovation Solution
Control the concentration of carbon and chlorine impurities within specific ranges (1x10^14 to 3x10^17 atoms/cm^3 for carbon and 1x10^14 to 1x10^17 atoms/cm^3 for chlorine) during the hydride vapor phase epitaxy process at high temperatures (1200 °C or more) to achieve low absorption numbers and improved UV light transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HVPE method is used to manufacture single-crystalline AIN, then the substrate can be produced with good crystallinity, but the UV light transparency at 265 nm is insufficient due to high absorption
Solution Approach 1:
The patent applies parameter changes by precisely controlling the carbon concentration to 1×10^14 to 3×10^17 atoms/cm³ and chlorine concentration to 1×10^14 to 1×10^17 atoms/cm³ within the crystal structure. This quantitative control of impurity parameters transforms the material properties to achieve both good crystallinity and high UV transparency at 265 nm, resolving the contradiction between structural quality and optical performance.
Solution Approach 2:
The patent applies local quality by differentiating the acceptable concentration ranges for different impurity elements. Carbon and chlorine are controlled within specific low concentration ranges to maintain UV transparency, while other impurities are allowed within broader limits. This selective quality control enables the substrate to simultaneously achieve good crystallinity and high light transmission.
2Object-affected harmful factors
If impurity concentration is reduced to improve UV transparency, then light absorption decreases, but manufacturing complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for carbon (1×10^14 to 3×10^17 atoms/cm³) and chlorine (1×10^14 to 1×10^17 atoms/cm³) concentrations that optimize UV transparency while remaining achievable through conventional HVPE manufacturing. This quantified approach transforms an abstract quality requirement into controllable manufacturing parameters.
Solution Approach 2:
The patent applies partial action by not requiring complete elimination of impurities, but rather controlling them within specific concentration ranges. This partial control approach achieves the necessary UV transparency improvement without requiring excessively complex purification processes, balancing optical performance with manufacturing feasibility.
3Reliability
If high temperature growth (1200°C or more) is used to improve crystallinity, then crystal quality increases, but carbon and chlorine impurity control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by defining precise impurity concentration windows (carbon: 1×10^14 to 3×10^17 atoms/cm³, chlorine: 1×10^14 to 1×10^17 atoms/cm³) that can be achieved through high temperature growth. These parameter specifications guide the manufacturing process to maintain both high crystallinity and acceptable impurity levels despite the challenges of high temperature processing.
Solution Approach 2:
The patent applies feedback by establishing measurable impurity concentration thresholds that provide clear criteria for process control and quality assessment. The specified concentration ranges enable real-time monitoring and adjustment of the HVPE process to maintain both high temperature growth benefits and impurity control requirements.
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 approach results in single-crystalline AIN with enhanced UV light transparency at 265 nm, suitable for UV LED applications, by reducing nitrogen vacancies and maintaining good crystallinity, even with relatively high total impurity concentrations.
Implementation Method 1
a method to manufacture the single-crystalline AIN using hydride vapor phase epitaxy method (HVPE method)
Implementation Method 2
growth at a high temperature by HVPE method
Data Source
AI summary
The present invention relates to an aluminum nitride single crystal characterized in that the concentration of carbon is 1x1014 atoms/cm3, the concentration of chlorine is 1x1014 to 1x1017 atoms/cm3, and the absorption coefficient at a wavelength of 265 nm is 40 cm-1 or less.