Effect of stack number on the threshold current density and emission wavelength in quantum dash/dot lasers

InAs quantum dash and dot (QDH and QD) lasers grown by molecular beam epitaxy on InP substrate are studied. The grown lasers with active zone containing multiple stacked layers exhibit lasing wavelength at 1.55 μm. On these devices, the experimental threshold current density reaches its minimum value for a double stacked QDH/QD structure. Other basic laser properties like gain and quantum efficiency are compared. QD lasers exhibit better threshold current densities but equivalent modal gain per layer than QDH. Finally, the analysis of the modal gain on QD laser structures shows a promising potential for improvement of the laser properties.