Nitride Crystal Substrate With Controlled IR Absorption
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Solution Overview
Problem
Conventional nitride crystal substrates have an uncontrollable absorption coefficient in the infrared region due to dislocation scattering, making it difficult to inspect the quality of the crystal using reflection spectra measured by infrared light.
Innovation Solution
A nitride crystal substrate with group-III nitride crystal containing n-type impurities, where the absorption coefficient is expressed by the equation α = Ne * K * λ^a in the wavelength range of 1 μm to 3.3 μm, with constants 1.5×10^-19 ≤ K ≤ 6.0×10^-19 and a = 3, ensuring an error of ±0.1α at 2 μm, and no peak within 1,200 cm^-1 to 1,500 cm^-1 in the reflection spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional nitride crystal substrates are used, then substrate heating can be performed, but the absorption coefficient in the infrared region cannot be well controlled due to dislocation scattering
Solution Approach 1:
The patent changes the physical parameters of the nitride crystal substrate by controlling the carrier concentration (Ne) within a specific range (1×10^17 cm^-3 to 1×10^19 cm^-3) and managing dislocation density (below 1×10^8 cm^-2). By adjusting these parameters, the absorption coefficient in the infrared region can be precisely controlled to follow the relationship α = Ne × K × λ^a, enabling reliable crystal quality inspection through reflection spectrum measurement.
2Productivity
If dislocation scattering is present in the nitride crystal substrate, then crystal growth can proceed, but the absorption coefficient becomes uncontrollable and affects heating characteristics
Solution Approach 1:
The patent establishes specific parameter ranges for carrier concentration (1×10^17 cm^-3 to 1×10^19 cm^-3) and dislocation density (below 1×10^8 cm^-2) to achieve optimal balance between crystal growth and absorption coefficient control. Within these parameter ranges, the absorption coefficient follows a predictable relationship with wavelength and carrier concentration, enabling precise control while maintaining productive crystal growth.
Solution Approach 2:
The patent replaces direct measurement and control of absorption coefficient with indirect control through carrier concentration management and dislocation density control. By measuring reflection spectra and analyzing the relationship between carrier concentration and absorption characteristics, the patent enables precise control without requiring direct mechanical or physical intervention in the absorption process.
3Temperature
If the absorption coefficient is not well controlled, then substrate heating can be performed, but the heating characteristics and reflection spectrum shape are affected
Solution Approach 1:
The patent controls the absorption coefficient by managing carrier concentration (Ne) and dislocation density, establishing a predictable relationship α = Ne × K × λ^a. This parameter control ensures that when infrared light irradiates the substrate for heating, the absorption characteristics remain stable and predictable, allowing accurate substrate temperature control and reliable reflection spectrum measurement for crystal quality inspection.
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 absorption coefficient is accurately controlled, allowing for precise heating and inspection of the crystal quality, with improved reproducibility and uniformity in heating efficiency, leading to better semiconductor device performance.
Implementation Method 1
an absorption coefficient of the nitride crystal substrate in an infrared region is an important physical property value that affects, for example, the heating characteristics of the substrate
Implementation Method 2
in a reflection spectrum measured by irradiating the nitride crystal substrate with infrared light, there is no peak with a peak top within a wavenumber range of 1,200 cm^-1 or more and 1,500 cm^-1 or less
Data Source
AI summary
There is provided a nitride crystal substrate constituted by group-III nitride crystal, containing n-type impurities, with an absorption coefficient α being approximately expressed by equation (1) by a least squares method in a wavelength range of at least 1 μm or more and 3.3 μm or less.α=NeKλa (where 1.5×10-19≤K≤6.×10-19,a=3),(1)here, a wavelength is λ (μm), an absorption coefficient of the nitride crystal substrate at 27° C. is α (cm−1), a carrier concentration in the nitride crystal substrate is Ne (cm−3), and K and a are constants, wherein an error of an actually measured absorption coefficient with respect to the absorption coefficient α obtained from equation (1) at a wavelength of 2 μm is within +0.1α, and in a reflection spectrum measured by irradiating the nitride crystal substrate with infrared light, there is no peak with a peak top within a wavenumber range of 1,200 cm−1 or more and 1,500 cm−1 or less.