Relationship between crystallographic orientation and 3.42 eV emission bands in GaN grown by HVPE on Si substrate

The relationship between the 3.42 eV emission band in GaN and its crystallographic orientation was investigated. The peak position of the band shifts to lower energies with increase of the film thickness. The basal and/or pyramidal plane oriented GaN layers had a lower band intensity than those of prismatic plane oriented GaN films, and the polycrystalline structured GaN film showed both strong and neutral donor bound exciton band intensities. The band in GaN gradually shifted to lower energies with an increase of the luminescence intensity of the excitonic band indicating that the band in GaN is not at a fixed energy level, but depends upon its crystal structural qualities.