Submilliamp-threshold InGaAs/GaAs quantum-well ridge-waveguide lasers with impurity-induced disordering

We report a significant reduction of threshold current in lasers from a material which has two strained-layer In/sub 0.2/Ga/sub 0.8/As/GaAs QW inside a linearly-graded-index separate-confinement waveguide structure. The ridges were etched by Cl/sub 2/ reactive ion etching. Self-aligned Si deposition and Zn diffusion were used in the device fabrication. The resultant active stripe width was controlled by the Si diffusion time. For example, a 0.3-/spl mu/m-wide active stripe was achieved from the originally 1.5-/spl mu/m-wide device after a 90 min diffusion at 850 C. As a result, threshold currents as low as 0.7 mA for pulsed operation and 0.9 mA for cw operation have been obtained from an uncoated 137-/spl mu/m-long and 0.3-/spl mu/m-wide device without special heat sinking treatment.