Present and future aspects of blue light emitting devices

High brightness InGaN single-quantum-well structure (SQW) blue and green light-emitting diodes (LEDs) with luminous intensities of 2 and 10 cd have been achieved and commercialized. Also, InGaN multi-quantum-well structure laser diodes (LDs) were fabricated for the first time. These LDs emitted coherent light at 390–440 nm from an InGaN based multi-quantum-well structure at room temperature. The emission of the SQW LEDs is caused from a recombination of excitons localized at certain potential minima in the quantum well. Also, the lasing of the MQW LDs seems to originate from localized excitons as much as from many-body Coulomb effects.