Suboxide Molecular-Beam Epitaxy for High-Growth Oxide Films
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Solution Overview
Problem
Conventional molecular-beam epitaxy (MBE) techniques for growing oxide films, such as gallium oxide (Ga2O3), are limited by the formation and desorption of volatile suboxides, leading to reduced growth rates and crystal defects due to oxygen deficiency in the adsorption-controlled growth regime.
Innovation Solution
The use of a molecular beam of a suboxide, which is subsequently oxidized in a single step reaction to form an oxide film, employing a source mixture of elemental gallium and gallium oxide with controlled ratios and heating to produce a high-purity suboxide beam, allowing for increased growth rates and improved crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MBE techniques are used to grow oxide films in adsorption-controlled regime, then crystal quality is improved, but growth rate is reduced due to formation and desorption of volatile suboxides
Solution Approach 1:
The patent applies preliminary action by pre-forming suboxide species (Ga2O) in the molecular beam source before delivery to the substrate. The source mixture of Ga and Ga2O3 is heated to generate a molecular beam rich in Ga2O species, which then oxidize on the substrate surface to form Ga2O3 film. This preliminary formation of reactive suboxide species in the beam ensures high crystal quality while maintaining fast growth rates up to 5 μm/hr.
2Shape
If excess source metal is supplied to achieve adsorption-controlled growth, then surface morphology is improved, but volatile precursor species form and desorb
Solution Approach 1:
The patent converts the harmful effect of volatile suboxide formation into a beneficial process. Instead of treating Ga2O desorption as a loss mechanism to be avoided, the invention utilizes Ga2O as the primary transport species in the molecular beam. The suboxide species are deliberately generated in excess in the source, and their controlled oxidation on the substrate surface converts them into the desired Ga2O3 film, turning the previously harmful volatility into a useful transport and deposition mechanism.
3Stability of the object's composition
If there is not enough active oxygen species to oxidize suboxides, then adsorption-controlled regime is maintained, but growth rate is limited
Solution Approach 1:
The patent applies parameter changes by modifying the oxygen partial pressure and oxygen flux during growth. The process operates at low oxygen partial pressure (10^-6 to 10^-3 Torr) with controlled oxygen flux to maintain adsorption-controlled conditions. This parameter optimization ensures sufficient oxygen for complete oxidation of Ga2O to Ga2O3 while maintaining the adsorption-controlled regime, achieving both high crystal quality and fast growth rates up to 5 μm/hr.
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 high growth rates of up to 5 microns per hour with reduced crystal defects and improved crystal quality, surpassing conventional MBE limitations and achieving results comparable to other established growth methods like CVD or MOVPE.
Implementation Method 1
The source mixture may be heated to produce the molecular beam
Implementation Method 2
Molecular-beam epitaxy (MBE) involves the growth of epitaxial thin films from molecular beams of source materials
Implementation Method 3
growing a oxide film of the element by oxidizing the suboxide with the oxidant species
Data Source
AI summary
Molecular-beam epitaxy (MBE) and more particularly suboxide MBE (S-MBE) and related structures are disclosed. S-MBE is disclosed that includes the use of a molecular beam of a suboxide that may be subsequently oxidized in a single step reaction to form an oxide film. By way of example, for a gallium oxide (Ga2O3) film, a molecular beam including a suboxide of gallium (Ga2O) may be provided. S-MBE may be performed in adsorption-controlled regimes where there is an excess of source material containing species in order to promote high growth rates for oxide films with improved crystallinity. Source mixtures for providing molecular beams of suboxides are disclosed that include mixtures of a particular element and an oxide of the element in ratios that promote such adsorption-controlled growth regimes. Related structures include oxide films having increased thickness with reduced crystal defects, including single polymorph films of gallium oxide.