Fig. 1. (a) Schematic diagram of the GaAsBi/GaAs single QW structure. (b) TEM image showing the as-grown 15 nm thick single GaAsBi/GaAs QW. (c) TEM image showing the same QW after RTA.

Fig. 2. Fabrication process of the GaAsBi microdisk. The electron beam lithography resist Zep520 is directly spin-coated on the wafer, with subsequent inductively coupled plasma-reactive ion etching transferring the disk pattern down to the active layer. Finally, the AlGaAs sacrificial layer is oxidized and then undercut by hydrofluoric acid for the free-standing disk.

Fig. 3. (a) Cold disk cavity oscillates with the gain QW structure resulting in the lasing behavior with a good consistency of FSR between theoretical and experimental (pumping of 101.2 μW) results. The inset is the FDTD simulation for mode profiles of lasing wavelengths 1276 nm and 1407 nm, respectively. (b) GaAsBi QW PL well covers the wavelength range from 1100 to 1400 nm. (c) The evolution of PL spectra of the GaAsBi microdisk laser of radius 0.75 μm at various pumping power.

Fig. 4. (a) Scanning electron microscopy images of a fabricated GaAsBi microdisk laser at different radii. (b) The collected PL spectra for the GaAsBi microdisk laser with a radius of 0.75, 1.00, and 1.50 μm with related L–L curves and FWHMs. The chosen peak is indicated by a black arrow. For the smallest radius of 0.75 μm, the lasing threshold is 1.2 μW and the FWHM is 2.5±0.3  nm.