A systematic investigation into the conversion of β-Ga2O3 to GaN nanowires using NH3 and H2: Effects on the photoluminescence properties

Abstract

GaN nanowires (NWs) with a hexagonal wurtzite crystal structure, diameters of 50 nm and lengths of 10 μm have been obtained from postgrowth nitridation of monoclinic β-Ga2O3 NWs using NH3 between 700–1090 °C. The conversion of β-Ga2O3 to GaN NWs has been investigated in a systematic way by varying the temperature, gas flows and nitridation times using Ar or N2:10% H2. We find that nitridation is most effective at temperatures ≥900 °C using NH3 with N2:10% H2 which promotes the efficient conversion of β-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 β-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 τ≈0.35 ns in all cases. In contrast the nitridation of β-Ga2O3 NWs using NH3 and Ar is less effective. Therefore, H2 is essential in removing O2 and also effective since it lead to the complete elimination of the β-Ga2O3 NWs at 1000 °C in the absence of NH3.