Present status of InGaN-based UV/blue/green LEDs and laser diodes
InGaN quantum well structure light emitting diodes operating with external quantum efficiencies of 7.5% at 371 nm (UV), 11.2% at 468 nm (blue) and 11.6% at green were developed. The blue and green InGaN LEDs with lurninous efficiencies of 5 lm/W and 30 lm/W can be used for fabricating white LEDs with a lumininous efficiency of 30 lm/W which is almost identical to that of conventional incandescent bulb lamps. Epitaxially laterally overgrown GaN on sapphire was used to reduce the number of threading dislocations originating from the interface of the GaN epilayer with the sapphire substrate. The GaN layer above the SiO2 mask area surrounding the window and corresponding to the lateral overgrowth, was nearly free of the threading dislocations. InGaN multi-quantum well structure laser diodes grown on pure GaN substrates, which were fabricated by removing the sapphire substrate, were demonstrated. The laser diodes with an output power of 5 mW exhibited a lifetime of more than 290 hours. The far-field pattern of the laser diodes with a cleaved mirror facet revealed single mode emission without any interference effects.
KeywordsSapphire Substrate External Quantum Efficiency Luminous Efficiency Threshold Current Density Single Quantum Well
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