Voltage-controlled yellow or orange emission from GaN codoped with Er and Eu

Orange and yellow-colored light emission has been achieved at room temperat ure in the same elecroluminescent device (ELD) made on GaN thin films codop ed with Er and Eu. The GaN film was grown by molecular-beam epitaxy on Si ( 111) substrates using solid sources for Ga, Er and Eu and a plasma source f or N-2. Simple Schottky devices were fabricated on the GaN films using indi um-tin oxide (ITO) transparent electrodes. ELD spectra show that the yellow and orange colors result from the combination of green emission from Er (5 37, 558 nm) and red emission from Eu (621 nm). A color change was observed with applied bias, producing yellow at higher bias (-100 V) and orange at l ower bias (-70 V). We have fabricated both relatively small (similar to 250 mu m) and large (1.45 mm) ELDs. Parameters for the chromaticity diagram we re calculated to be x=0.382, y=0.605 for the yellow emission and x=0.467, y =0.523 for the orange emission. This work shows the possibility of achievin g any intermediate color in the spectrum from green to red by adjusting the concentration of Er and Eu in GaN. (C) 2000 American Institute of Physics. [S0003-6951(00)04312-6].