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

We report on the fabrication as well as on the optical and electrical characterization of violet and blue GaN/InGaN/AlGaN double heterostructure light emitting diodes (DH LEDs) covering the 385–430 nm spectral range. MOCVD grown epitaxial layer sequences were processed into mesa diodes by chemically assisted ion-beam etching and contact metallization. To achieve packaged LED devices the diode chips were encapsulated in transparent epoxy resin using standard technology. Based on blue emitting diodes as primary light sources, white luminescence conversion LEDs (LUCOLEDs) have been fabricated. Using commercially available perylene dyes or YAG:Ce phosphors as the luminescent material, the LED radiation is converted into light of longer wavelengths by luminescence down-conversion (Stokes shift). In contrast to conventional LEDs which only emit quasi-monochromatic light, light of nearly all colors can be generated by this technique. By mixing the primary blue light with the radiation emitted from the converting material, also white and mixed colors have been generated.