Despite the excellent crystal quality, below bandgap optical absorption bands in the blue/UV range affect the UV transparency of wafers. We use density functional theory (DFT) to develop a model to understand the interplay of point defects responsible for this absorption. We show a direct dependence of the mid-gap absorption band with the carbon concentration within the AlN.

Low defect density AlN and AlGaN epitaxial films are grown upon these wafers that exhibit superior optical properties in terms of emission efficiency and line width and can be doped with an efficiency that is several orders of magnitude higher than possible in technologies using non-native substrates. UV LED structures and laser diodes were fabricated on these materials that exhibit low turn-on voltages and record low lasing threshold.

This presentation will review state-of-the-art of AlN-based technology and give examples of potential applications in future devices and contrast these with other wide bandgap technologies.

1. FULLTEXT: Growth of AlN crystals and AlGaN epitaxy on AlN wafers, PDF document, version 1.3, 4.2MB

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1. Preparation of free-standing GaN substrates from thick GaN layers crystallized by Hydride Vapor Phase Epitaxy on ammonothermally grown GaN seeds