N-type GaN Crystal Growth via Carbon-Mediated Germanium Doping
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Solution Overview
Problem
Conventional methods for producing n-type Group III nitride-based compound semiconductors using the flux process face difficulties in achieving high electron concentration and crystallinity, particularly when using germanium as a donor, as excessive germanium addition inhibits crystal growth and low germanium incorporation results in poor semiconductor quality.
Innovation Solution
Dissolving carbon and germanium in the melt during the flux process, where germanium acts as a donor, allowing for the growth of n-type Group III nitride-based compound semiconductors with controlled resistivity and high electron concentration by optimizing the mole percentage of germanium to gallium and carbon to sodium ratios, ensuring effective incorporation of germanium without carbon contamination in the final crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If germanium is added to the flux process for producing n-type GaN, then electron concentration is improved, but crystal growth is inhibited and crystallinity deteriorates
Solution Approach 1:
Carbon is introduced as an intermediary substance that facilitates germanium incorporation into the GaN crystal lattice. The carbon serves as a catalyst or mediator that enables Ge atoms to substitute Ga atoms without directly incorporating into the final crystal structure, thus allowing high electron concentration while maintaining good crystallinity. This resolves the contradiction by providing a pathway for donor incorporation that doesn't harm crystal growth.
Solution Approach 2:
The invention changes the chemical composition parameters of the flux system by adding carbon to the traditional Na-Ga-C system, creating a Na-Ga-C-Ge system. This parameter change enables new reaction pathways where carbon facilitates germanium incorporation. By adjusting the concentrations of carbon and germanium in the flux, the process achieves optimal electron concentration while preserving crystal quality, thus resolving the contradiction between doping efficiency and crystallinity.
2Quantity of substance
If carbon is added to facilitate germanium incorporation, then donor incorporation is improved, but carbon contamination may occur
Solution Approach 1:
The invention converts the potential harmful effect of carbon into a beneficial catalytic function. Instead of treating carbon as an unwanted impurity to be avoided, the process deliberately introduces carbon as a necessary component that enables germanium incorporation. The carbon serves a functional role in facilitating Ge substitution of Ga, and through optimized process control, the carbon remains in the flux rather than contaminating the crystal, thus transforming a potential harm into a benefit.
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 method achieves n-type GaN crystals with high electron concentration (1×10^17/cm^3 to 5×10^19/cm^3), low resistivity (0.001 Ω·cm to 0.1 Ω·cm), and improved crystallinity, suitable for electronic devices, by effectively incorporating germanium as a donor while maintaining high transparency and quality.
Implementation Method 1
Group III element substitution with germanium serving as a donor
Implementation Method 2
germanium is incorporated as a donor into the semiconductor crystal
Implementation Method 3
carbon catalyzes substitution of the Group III element with germanium
Implementation Method 4
growing an n-type Group III nitride-based compound semiconductor crystal on a seed crystal from the melt
Data Source
AI summary
An object of the present invention is to realize, by the flux process, the production of a high-quality n-type semiconductor crystal having high concentration of electrons. The method of the invention for producing an n-type Group III nitride-based compound semiconductor by the flux process, the method including preparing a melt by melting at least a Group III element by use of a flux; supplying a nitrogen-containing gas to the melt; and growing an n-type Group III nitride-based compound semiconductor crystal on a seed crystal from the melt. In the method, carbon and germanium are dissolved in the melt, and germanium is incorporated as a donor into the semiconductor crystal, to thereby produce an n-type semiconductor crystal.The mole percentage of germanium to gallium in the melt is 0.05 mol % to 0.5 mol %, and the mole percentage of carbon to sodium is 0.1 mol % to 3.0 mol %.