Improved AlxGa1−xAs bulk lasers with superlattice interfaces

A graded superlattice composed of AlxGa1−xAs and GaAs having a total thickness of 150 A was incorporated on each side of the active layer of an otherwise standard double heterojunction laser. In spite of no optimization, current threshold densities as low as 600 A/cm2 at 880 nm were obtained in broad area devices with 300‐μm cavity lengths. Otherwise identical structures with abrupt heterointerfaces in place of a graded superlattice exhibited current threshold densities in the range 1.2–1.4 kA/cm2. Silicon and beryllium were used for n‐ and p‐type dopants. These results represent the best values for bulk laser and are attributed to improved interfaces primarily that between the bottom confining layer (substrate side) and the active layer.