ELECTROLUMINESCENT DEVICES FABRICATED ON ERBIUM DOPED GaN
Visible and infrared (IR) rare-earth-activated light emission has been obtained from Er-doped GaN electroluminescent devices (ELD). The ELD structure consists of an in-situ Er-doped GaN layer grown on either a sapphire or silicon (Si) substrate, using indium tin oxide (ITO) transparent electrodes. The GaN film was grown by molecular beam epitaxy using solid sources for Ga and Er and a plasma source for N2. The temperature dependence of the light emission and the current conduction is reported. The EL spectrum shows two main visible peaks at 537 and 558 nm and a group of closely spaced IR peaks clustered around 1550 nm. All emission lines correspond to Er3+ 4-f inner shell transitions from excited states (with energies less than the bandgap of GaN) to the 4I15/2 ground level. The ELD emission peaks are narrow (~6 nm in the visible and ~30 nm in the IR). The green visible spectrum data indicate that the 558 nm transition is dominant below 250K, whereas the 537 nm transition is dominant at higher temperature peaking at 300K. Temperatures from 240-500K have minimal effect on IR emission intensity. A simple model consisting of two back-to-back Schottky diodes explains the current-voltage (I-V) dependence. The effect of Er doping and substrate type on carrier transport is investigated as a function of voltage and temperature. Specifically, there is evidence that an Er-related defect is responsible for carrier generation at temperatures above 300K. The effect of bias polarity on spatial confinement of the light emission in different areas of the devices is discussed. The proposed model indicates that both electric field intensity and current density are important in producing light emission. The model also accounts for the uniformity of the emission under the electrodes when considering the type of substrate (silicon or sapphire) used for GaN:Er device growth.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:erbium full color display light emitting device optical amplifier
Date of Publication:01/01/2001