Enhancement of blue emission from GaN films and diodes by water vapor remote plasma treatment

We have studied the effects of water vapor remote plasma treatment (H₂O RPT) on emission from Si-doped and undoped n-type GaN films grown on c-face sapphire substrates by the atmospheric-pressure metalorganic chemical vapor deposition method. We found by photoluminescence (PL) spectroscopy at 77 K that H₂O RPT enhanced violet emission from the n-type GaN films, similarly to the previously observed enhancing effect on blue emission from Mg-doped p-type GaN films. We also observed that H₂O RPT reduced the intensity of ESR signal comprising of two peaks detected at 4.2 K in undoped n-type films and increased their resistivity measured at room temperature. We ascribe the enhancing effect of H₂O RPT to the passivation of non-radiative recombination centers by hydrogen produced by H₂O RPT. We formed GaN p-n diodes from the layer structure of p-GaN:Mg/n-GaN:Si/sapphire, and carried out electroluminescence (EL) measurements of the diodes at 77 K. We observed that EL intensity was also enhanced by H₂O RPT.