A systematic investigation into the conversion of beta-Ga2O3 to GaN nanowires using NH3 and H-2: Effects on the photoluminescence properties

Abstract

GaN nanowires (NWs) with a hexagonal wurtzite crystal structure, diameters of 50 nm and lengths of 10 mu m have been obtained from postgrowth nitridation of monoclinic beta-Ga2O3 NWs using NH3 between 700-1090 degrees C. The conversion of beta-Ga2O3 to GaN NWs has been investigated in a systematic way by varying the temperature, gas flows and nitridation times using Ar or N-2 : 10% H-2. We find that nitridation is most effective at temperatures >= 900 degrees C using NH3 with N-2 : 10% H-2 which promotes the efficient conversion of beta-Ga2O3 to GaN, resulting into the enhancement of the band edge emission, suppression of the broad-band photoluminescence (PL) related to oxygen defects and the appearance of red emission due to deep-acceptorlike states. The gradual evolution of the PL spectra from that of beta-Ga2O3 to GaN exhibited a clear, systematic dependence on the nitridation temperature and gas flows and the band to band emission lifetime which was found to be tau approximate to 0.35 ns in all cases. In contrast the nitridation of beta-Ga2O3 NWs using NH3 and Ar is less effective. Therefore, H-2 is essential in removing O-2 and also effective since it lead to the complete elimination of the beta-Ga2O3 NWs at 1000 degrees C in the absence of NH3. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525562]