Photoluminescence (PL) spectra of GaN layers grown on sapphire substrates by metal-organic vapor phase epitaxy (MOVPE) were observed at temperatures from RT to 500 K. The spectra include the near-band-edge emission (NBE) and yellow luminescence (YL). The peak energy of the NBE is shifted towards lower energy with increasing observed temperature. UV light-emitting diodes (LEDs) utilizing band-gap narrowing due to thermal effects are proposed and their advantages for integration are discussed. (c) 2006 Elsevier B.V. All rights reserved.