GaAs Microdisk Lasers with Al₂O₃ Passivation Selectively Grown on SOI

The development of Si photonics requires efficient on-chip light sources to achieve low-cost and high-throughput systems. One promising approach is direct epitaxy of III–V materials on Si using selective growth, which has attracted extensive attention. The lateral aspect ratio trapping (LART) growth technique is used to monolithically integrate III–V materials with adjustable dimensions and without the need for thick transition buffer layers on Si. It also enables easy light coupling between selectively grown lasers and Si-based waveguides and provides various dimensions for diverse device fabrication. In this study, we report the characteristics of low-threshold optically pumped GaAs microdisk lasers (MDLs) on Si-on-insulator (SOI) grown by the LART technique. We investigated the effect of the Al2O3 passivation layer on the laser performance, including deposition temperature and thickness of the passivation. Under pulsed optical pumping, the MDLs exhibited room-temperature lasing with a low threshold down to 80 μJ/cm2. The highest operating temperature of the device was 85 °C. Our study demonstrates the potential of GaAs LART on an SOI platform for future dense integration. The fabrication of microlasers with whispering gallery mode cavities shows that this approach can enable the development of efficient on-chip laser sources for Si photonics.