Huge Bandgap-Bowing Effect in III-V-N Type Nitride Alloy Semiconductors and its Applications

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This research project has realized III-V-N type nitride alloy semiconductors such as GaAsN, GaPN, InAsN, GaAsPN, InGaAsN and InGaPN, with N concentrations far beyond the thermodynamic equilibrium limit using metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) as efficient epitaxial growth methods. Epitaxial growth conditions have been established for alloy layers with high structural and optical qualities which are reasonably applicable to devices. Structural properties such as compositional inhomogeneity and defects have been clarified in relation to N concentrations and growth conditions. It has been found that optical properties near the band edge are significantly affected by localized states which are originated by isolated or clustered N atoms at diluted N concentration regions. It has been found that huge bandgap bowing effect is a characteristic feature common in all the III-V-N type alloys. The bandgap bowing parameters have been established for each III-V-N ternary and quaternary alloy. Quantum-well structures involving III-V-N type alloys have been investigated, and shown that with a proper choice of heterostructure will give an efficient electron confinement to quantum wells due to higher band offsets.