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Silicon photonics has been longing for an efficient on-chip light source that is electrically driven at room temperature. Microdisk laser featured with low-loss whispering gallery modes can emit directional lasing beam through a closely coupled on-chip waveguide efficiently, and hence is particularly suitable for photonics integration. The realization of electrically pumped III-nitride microdisk laser grown on Si has been impeded by the conventional undercut structure, poor material quality, and a limited quality of GaN microdisk formed by dry etching. Here we report a successful fabrication of room-temperature electrically pumped InGaN-based microdisk lasers grown on Si. A dramatic narrowing of the electroluminescence spectral line-width and a clear discontinuity in the slope of light output power plotted as a function of the injection current provide an unambiguous evidence of lasing. This is the first observation of electrically pumped lasing in InGaN-based microdisk lasers grown on Si at room temperature.

By observing the morphology evolution of green InGaN/GaN quantum well (QW) and studying the catholuminescence (CL) property, we investigate indium-segregation-related defects that are formed at green InGaN/GaN QW interfaces. Meanwhile, we also propose the approach and suggest the mechanism to remove them for green InGaN/GaN QW grown on both GaN templates and free-standing GaN substrates. By engineering the interface of green InGaN/GaN QWs, we have achieved green laser diode (LD) structure with low threshold current density of 1.85 kA cmsup-2/sup. The output power of the green LD is 58 mW at a current density of 6 kA cmsup-2/supunder continuous-wave operation at room temperature.

Low threshold continuous-wave (CW) lasing of current injected InGaN quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs) was achieved at room temperature. The VCSEL was fabricated by metal bonding technique on a copper substrate to improve the heat dissipation ability of the device. For the first time, lasing was obtained at yellow-green wavelength of 560.4 nm with a low threshold of 0.61 mA, corresponding to a current density of 0.78 kA/cm2. A high degree of polarization of 94% were measured. Despite the operation in the range of "green gap" of GaN-based devices, single longitudinal mode laser emission was clearly achieved due to the high quality of active region based on InGaN QDs and the excellent thermal design of the VCSELs.