ABSTRACT
GaN-based materials such as GaN, InN, AIN and their alloys are useful for shortwavelength optical devices because they have a large direct band gap ranging from 1.96.2 eV. Among GaN-based materials, GalnN is suitable for the active layer of the visible light emitting diodes (LEDs) because of its direct band gap ranging from 1.9-3.4 eV.[l] GalnN quantum-well (QW) structure enhances its luminescence efficiency and is used in GaN-based LEDs and laser diodes. [2-4] High-brightness ultraviolet, blue, green LEDs are available using GalnN QW structures.[3,5] However, few research has been reported on the GaN-based longer wavelength LEDs (more than 590 nm).[6,7] There is a large advantage over the toxic InP-and GaAs-based longer wavelength LEDs, since GaN-based materials are not toxic. So, GaN-based longer wavelength LEDs are desired for the realization of the environmental friendly atmosphere.
