The advent of epitaxial techniques for growing thin films
has allowed for the growth of unnatural, metastable structures having properties
previously unattainable in equilibrium systems. Specifically, quaternary
compounds are of great interest for microelectronic and optoelectronic devices
due to expectations that these materials will exhibit the promising physical
(e.g. mechanical hardness, thermal expansion, close matching lattice parameters,
etc.) and electronic properties of their binary constituents. Indeed, quaternary
materials may not only have bandgaps intermediate to those of the constituent
binary systems, but in some cases, may even have direct bandgaps. Existing high
temperature synthetic methods, although of research importance, are not suitable
for commercial production of SiCAlN or other quaternary thin films comprising
Group IV and Group III elements.
Researchers at Arizona State University have developed a
method for depositing an epitaxial thin film having the quaternary formula YCZN
wherein Y is a Group IV element and Z is a Group III element on a substrate at
temperature between ambient and 1000°C in a gas source molecular beam epitaxial
(GSMBE) chamber. This method provides high purity, low defect, device quality
quaternary epitaxial thin films, such as SiCAlN, for deposition on silicon and
silicon carbide substrates. These films demonstrate bandgaps ranging from 2 eV
to 6 eV with a spectral range from visible to ultraviolet. Also, the quaternary
compounds may function as a superhard coating material.
Potential Applications
- Microelectronics
- Optoelectronics
Benefits and Advantages
- Provides a Means for Commercial Quaternary Thin Film
Production ? allows for fabrication of high purity, low defect, device quality
quaternary epitaxial thin flims (e.g. SiCAlN, GeCAlN, etc.)
- Demonstrates Positive Physical Properties (e.g.
mechanical hardness, thermal expansion, close matching lattice parameters,
etc.) ? functional as a superhard coating material
- Demonstrates Positive Electronic Properties (e.g.
intermediate range bandgap compared to binary constituents, potential for
direct bandgaps, etc.) ? bandgaps range from 2 eV ? 6 eV; spectral range
from visible to ultraviolet
- Demonstrates Positive Physical Properties (e.g.
- Operates in Substantially Improved Temperature Range
(Ambient – 1000°C) ? alternative approaches require temperatures as high as
2100°C