Low Threshold GaN-Based Microdisk Lasers on Silicon With High Q Factor

III-nitride-based microdisk lasers on Si offer the potential in large-scale monolithic Si-based photonic integrated circuits. Here, we demonstrate a new approach to fabricating III-nitride microdisk lasers on Si, which can avoid the problem of low crystal quality and large thickness in traditional Si-based photonic devices. The III-nitride membrane was grown on a sapphire substrate and then transferred to Si to fabricate the microdisk lasers; and an airgap undercut structure was realized by simply wet etching of a SiO
₂
sacrificial layer. Devices fabricated by this method are free from the defect-rich layers that are unavoidable when grown directly on Si, resulting in a high quality (Q) value of 12543 at 412.9 nm. Room temperature lasing was demonstrated with a threshold energy density as low as 33.6 μJ/cm
²
. The whispering gallery mode oscillation was clearly observed and the model behavior was systematically investigated.