Three-color integration on rare-earth-doped GaN electroluminescent thin films

Lateral color integration has been obtained using GaN thin films doped with Er and Eu. These rare-earth doped GaN (GaN:RE) films were grown on Si (111) substrates by molecular beam epitaxy. Independent red and green emissions have been obtained from side-by-side Er and Eu electroluminescent devices. Photoluminescence and electroluminescence operation show green emissions at 537 and 558 nm from Er-doped GaN and red emission at 621 nm from Eu-doped GaN. Two patterning fabrication techniques have been investigated to obtain lateral integration: (a) use of shadow masks during 400 °C growth of GaN:RE films; (b) photoresist liftoff in conjunction with <100 °C GaN:RE growth. Devices fabricated by the shadow mask method were bright enough to be detected under the ambient light at a bias of 30 V. The GaN:RE films were clear and their surfaces were smooth with nanoscale GaN grains. The root mean square surface roughness was measured to be 5–10 nm.