Beta-Ga2O3 Substrate B-Axis Growth via EFG and Reflective Plate

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Solution Overview

Problem

Conventional methods for growing β-Ga2O3-based single-crystal substrates often result in significant variations in crystal structure, particularly along the b-axis direction, which affects the quality and consistency of the substrates.

Innovation Solution

The use of an Edge-defined Film-fed Growth (EFG) method with an after-heater and reflective plate in the crystal manufacturing apparatus helps reduce temperature gradients and dislocation density, resulting in a β-Ga2O3-based single-crystal substrate with minimal crystal structure variation by growing the crystal in the b-axis direction and employing Group IV elements like Sn or Si as dopants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional FZ technique with thermally meltable control additive is used, then temperature difference between center and outer portion is reduced, but the center portion is not solidified easily and crystal structure variation occurs

Engineering Contradiction:

Improvetemperature difference between center and outer portionVSAvoidcrystal structure uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent changes the growth method from FZ to EFG technique and modifies the dopant selection criteria (excluding thermally meltable elements like Si, Sn, Zr, Hf, Ge), thereby changing the thermal and structural parameters of crystal growth to achieve both temperature uniformity and structural precision

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and removes the harmful effect of thermally meltable control additives that cause center portion solidification difficulties, while retaining the beneficial temperature uniformity effect through alternative growth control mechanisms in EFG technique

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If SiO2 is used as dopant in EFG technique, then dopant amount is easy to control, but crystal structure variation along b-axis direction occurs

Engineering Contradiction:

Improvedopant amount controlVSAvoidcrystal structure uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the dopant selection parameter by excluding SiO2 and other thermally meltable elements, while maintaining EFG growth technique, thereby changing the chemical composition parameter to achieve both easy control and structural uniformity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different dopant strategies for different regions or growth stages, selecting non-thermally meltable dopants that provide localized control without causing overall crystal structure variation, particularly along the b-axis direction

Inventive Principle:

Principle #3Local 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 high-quality β-Ga2O3-based single-crystal substrates with reduced crystal structure variation, as evidenced by Δω and α values, enhancing their structural integrity and electrical characteristics.

Implementation Method 1

ωs represents an angle defined by an X-ray incident direction and the principal surface at a peak position of an X-ray rocking curve

Methodology Applied

Scientific EffectX-ray diffraction: X-Ray

Implementation Method 2

use of EFG (Edge-defined Film-fed Growth) technique to grow a flat-plate-shaped Ga2O3 single crystal

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a maximum value of Δω on an arbitrary straight line on the principal surface that passes through a center of the principal surface is not more than 0.7264

Methodology Applied

Scientific EffectTemperature gradient: Temperature Gradient

Implementation Method 4

use of an Edge-defined Film-fed Growth (EFG) method with an after-heater and reflective plate in the crystal manufacturing apparatus

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 5

comprising a dopant; wherein the dopant is a Group IV element

Methodology Applied

Scientific EffectDoping: Dopants

Implementation Method 6

Addition of the thermally meltable control additive increases infrared absorption properties of the β-Ga2O3-based single crystal

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Data Source

PatentUS10196756B2β-Ga2O3 single-crystal substrate

Publication Date: 2019.02.05 TAMURA KK

AI summary

A β-Ga2O3-based single-crystal substrate includes a β-Ga2O3-based single crystal, and a principal surface being a plane parallel to a b-axis of the β-Ga2O3-based single crystal. A maximum value of Δω on an arbitrary straight line on the principal surface that passes through a center of the principal surface is not more than 0.7264. The Δω is a difference between a maximum value and a minimum value of values obtained by subtracting ωa from ωs at each of measurement positions, where ωs represents an angle defined by an X-ray incident direction and the principal surface at a peak position of an X-ray rocking curve on the straight line and ωa represents an angle on an approximated straight line obtained by using least-squares method to linearly approximate a curve representing a relationship between the ωs and the measurement positions thereof.