Structure and luminescence of GaN layers

GaN films grown on (1 1 1) Si substrate by means of low pressure MOCVD tech nique in a horizontal flow quartz reactor are characterized by different th in layer analysis methods. The polycrystalline hexagonal structure of the G aN layers has been checked by means of grazing incidence X-ray diffractomet ry and IR spectroscopy. Cathodoluminescence (CL) spectra and their time kin etics are studied. The mean decay time of the 3,44 eV UV bound exciton tran sition is below I ns, whereas the 3.26 eV violet band shows a slow hyperbol ical decay over about I ps. A third yellow band appears at 2.12 eV due to t ransitions via localized states. (C) 2001 Elsevier Science B.V. All rights reserved.