Fabrication and characterization of GaN/InGaN/AlGaN double heterostructureLEDs and their application in luminescence conversion LEDs

We report on the fabrication as well as on the optical and electrical chara cterization of violet and blue GaN/InGaN/AlGaN double heterostructure light emitting diodes (DH LEDs) covering the 385-430 nm spectral range. MOCVD gr own epitaxial layer sequences were processed into mesa diodes by chemically assisted ion-beam etching and contact metallization. To achieve packaged L ED devices the diode chips were encapsulated in transparent epoxy resin usi ng standard technology. Based on blue emitting diodes as primary light sour ces, white luminescence conversion LEDs (LUCOLEDs) have been fabricated. Us ing commercially available perylene dyes or YAG:Ce phosphors as the lumines cent material, the LED radiation is converted into light of longer waveleng ths by luminescence down-conversion (Stokes shift). In contrast to conventi onal LEDs which only emit quasi-monochromatic light, light of nearly all co lors can be generated by this technique. By mixing the primary blue light w ith the radiation emitted from the converting material, also white and mixe d colors have been generated. (C) 1999 Elsevier Science S.A. All rights res erved.