Electroluminescence from Tm-doped GaN deposited by radio-frequency planar magnetron sputtering

Abstract

Room-temperature blue and near-infrared (NIR) electroluminescence ac (EL) has been demonstrated from Tm-doped GaN thin films prepared by rf planar magnetron sputter deposition. Blue and NIR EL emission peaks at ∼475 and ∼800 nm, respectively, were observed from the Tm3+ 4f intrashell transitions from the G41 and F43 excited states to the H63 ground state, respectively. The threshold voltage for the 475 nm blue emission was consistently 11 to 19 V higher than that for the 800 nm NIR emission. The EL intensity ratio of the 475 to 800 nm emission (I475/I800) was increased ∼900% with a 67% increase in the applied ac voltage from 120 to 200 V. These results indicate that the excitation process of EL from GaN:Tm ACTFEL devices is dominated by impact excitation of the Tm3+ luminescent centers by direct interaction between hot electrons and the ground state 4f electrons.