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 (I-D) in GaN and its cry stallographic orientation was investigated. The peak position of the I-D ba nd shifts to lower energies with increase of the film thickness. The basal and/or pyramidal plane oriented GaN layers had a lower I-D band intensity t han those of prismatic plane oriented GaN films, and the polycrystalline st ructured GaN film showed both strong I-D and neutral donor bound exciton (I -2) band intensities. The I-D band in GaN gradually shifted to lower energi es with an increase of the luminescence intensity of the excitonic I-2 band indicating that the I-D band in GaN is not at a fixed energy level, but de pends upon its crystal structural qualities.