Thermal characteristics are numerically investigated for the hybrid AlGaInAs/InP on silicon microring lasers with different ring radii and widths. Low threshold current and low active region temperature rise are expected for a microring laser with a narrow ring width. Based on the thermal analysis and the 3D simulation for mode characteristics, a hybrid AlGaInAs/InP on silicon microring lasers with an inner n-electrode laterally confined by the p-electrode metallic layer is fabricated using an adhesive bonding technique. A threshold current of 4 mA is achieved for a hybrid microring laser with a radius of 20 μm and a ring width of 3.5 μm at 12°C, and the corresponding threshold current density is as low as 1 kA∕cm². The influence of the location of silicon waveguide on output performance is studied experimentally for improving the output coupling efficiency. Furthermore, continuous-wave electrically injected lasing up to 55°C is realized for a hybrid microring laser with a radius of 30 μm and a ring width of 3 μm.China under grant 2012AA012202 and NSFC/RGC joint projectunder grant 61431166003. The authors thank Professor Andrew W. Poon and the Nanoelectronics FabricationFacility (NFF) of HKUST for support in the fabrication ofsilicon waveguides.