Application of AlAs-GaAs superlattices to step-index and graded-index waveguide separate-confinement heterostructure laser diodes

AlAs-GaAs superlattices were utilized for the waveguides in separate-confinement heterostructure laser diodes. A significantly low threshold current density Jth of 200 A/cm2 was achieved at a cavity length of about 500 μm for a graded-index superlattice-waveguide separate-confinement heterostructure laser diode. By photoluminescence measurements taken under a direct excitation condition, it was clearly demonstrated that the advantage of using the superlattice waveguide, i.e., the reduction of Jth value, is due to the improvement of heterointerface quality of the GaAs active layer. Moreover, a result on an all-binary SCH laser composed of the only AlAs and GaAs revealed that the Jth as considerably low as 400 A/cm2 was achieved at a cavity length of 400 μm.