We report on the fabrication and studies of Ø100 μm half-disk lasers with an active region based on InGaAs/GaAs quantum dots providing very high modal gain. Such resonators support whispering gallery modes propagating at the cavity periphery. The microlasers show directional light outcoupling: continuous-wave output power emitted from the flat side reaches 17 mW, which is about 7 times greater than the power emitted from the back semicircular side. Single-mode lasing in a wide range of the injection currents is observed. P-side down bonding of the devices onto Si-board allowed increasing the maximum optical power to more than 30 mW and the lasing was observed up to 93°C. The 3 dB modulation bandwidth of 4.6 GHz was measured likely being limited by RC-parasites.