Optical properties of InGaN multiple quantum well microdisks

摘要

Abstract: In$-0.22$/Ga$-0.78$/N/In$-0.06$/N multiple quantum well (MQW) microdisks with a size of 5.6 $mu@m in diameter have been fabricated by photolithography and ion beam etching. Time-resolved photoluminescence (PL) has been employed to study optical transitions in MQW structure and microdisk. The dominant emission from both MQW structures and microdisks were from localized exciton transitions. It was found in the microdisks that the low energy shoulder of the PL spectrum was quenched, and that the spontaneous emission line width was narrower while its intensity was enhanced with respect to that of the MQWs, which may be related to microcavity effects in the microdisks. A blue shift of the PL peak from the MQW microdisks compared with that in the MQW structures was also observed, and can be understood in terms of a reduced piezoelectric field due to strain relief in the microdisks. Microdisks with grating patterned micro- couplers around the disks edges were also fabricated by e- beam lithography to enhance light extraction from the microdisks. Near-field scanning optical microscopy was employed to make the near-field fluorescence images of the microdisks, which showed a strong emission preference in certain directions. The potential applications of III- nitride microdisks for optical interconnects and integration are also discussed. !25