GaAs Microdisk Lasers with Al<sub>2</sub>O<sub>3</sub> Passivation Selectively Grown on SOI

The development of Si photonics requires\nefficient on-chip light\nsources to achieve low-cost and high-throughput systems. One promising\napproach is direct epitaxy of III–V materials on Si using selective\ngrowth, which has attracted extensive attention. The lateral aspect\nratio trapping (LART) growth technique is used to monolithically integrate\nIII–V materials with adjustable dimensions and without the\nneed for thick transition buffer layers on Si. It also enables easy\nlight coupling between selectively grown lasers and Si-based waveguides\nand provides various dimensions for diverse device fabrication. In\nthis study, we report the characteristics of low-threshold optically\npumped GaAs microdisk lasers (MDLs) on Si-on-insulator (SOI) grown\nby the LART technique. We investigated the effect of the Al<sub>2</sub>O<sub>3</sub> passivation layer on the laser performance, including\ndeposition temperature and thickness of the passivation. Under pulsed\noptical pumping, the MDLs exhibited room-temperature lasing with a\nlow threshold down to 80 μJ/cm<sup>2</sup>. The highest operating\ntemperature of the device was 85 °C. Our study demonstrates the\npotential of GaAs LART on an SOI platform for future dense integration.\nThe fabrication of microlasers with whispering gallery mode cavities\nshows that this approach can enable the development of efficient on-chip\nlaser sources for Si photonics.