NEAR-BAND-EDGE TRANSITION IN ALUMINUM NITRIDE THIN-FILMS GROWN BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

Cathodoluminescence measurements were performed for carbon doped and u ndoped aluminum nitride thin films in the temperature range from liqui d helium to room temperature. The AIN films were grown on three differ ent substrates: 6H-SiC, 4H-SiC, and sapphire. From these samples, a st rong luminescence peak surrounded by two weaker peaks in the near band -edge region, near 6 eV, was observed. For AIN on sapphire, this near band-edge transition can be further resolved into three peaks at 6.11, 5.92, and 5.82 eV. These peaks are believed to be due to exciton reco mbination. The effects of substrate materials and carbon doping on the exciton peak were discussed. The temperature dependence of the peak p osition and line width of this transition was also studied. The temper ature coefficient of the band-gap energy is estimated to be 0.51 meV/K . (C) 1998 American Institute of Physics.