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.