Cathodoluminescence of AlN–GaN short period superlattices

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Abstract
Cathodoluminescence of AlN–GaN short period superlattice films was measured at 6 K, 77 K, and room temperature. The superlattice films were deposited using a switched atomic layer metalorganic chemical vapor deposition process onto a buffer layer of either AlN or GaN, which was deposited on basal plane sapphire substrates. The individual AlN and GaN layers of the superlattice films ranged in thickness from 2.6 to 20.8 Å. The cathodoluminescence of these samples was measured at several electron acceleration voltages to allow depth profiling of the samples. This allows the region of the sample (superlattice film, buffer layer, and substrate) from which the spectral features originate to be determined. A spectral peak in the ultraviolet region above the 3.5 eV band gap of GaN has been observed in all the superlattice samples studied to date. Our results indicate that the location of this peak is determined by quantum confinement in the GaN layers.