AlGaN photodetectors on Improved Substrates

UV (and blue) sensors have a wide range of commercial and Government applications. The III-V nitrides provide an attractive material system for such detectors, with bandgaps ranging from 2.0 to 6.2eV. While III-V nitride devices have made significantadvances, especially in the area of LEDs, defects continue to compromise the performance and lifetime of detectors and lasers. The major limiting factors are defects resulting from the differences in the lattice constant and thermal coefficient ofexpansion (TCE) of the substrate and the AlGaN active layers. This problem gets worse when the Al composition is increased to achieve a particular wavelength or bandgap. This proposal describes a novel approach to eliminate these defects, and make AlGaNwafers of large diameter at commercially acceptable cost which are TCE matched to the device layers and provide high thermal conductivity. The quality of this material will be demonstrated using AlGaN photodetectors. This development will result is aprocess to make large area AlGaN substrates with improved characteristics at a low cost, permitting widespread use of nitrides in both Government and commercial applications.