HIGH-PERFORMANCE PLANAR NATIVE-OXIDE BURIED-MESA INDEX-GUIDED ALGAAS-GAAS QUANTUM-WELL HETEROSTRUCTURE LASERS

High-performance planar "buried-mesa" index-guided AlGaAs-GaAs quantum well heterostructure (QWH) lasers have been fabricated by oxidation (H2O vapor + N2 car er gas, 425-525-degrees-C) of a significant thickness of the high composition AlxGa1-xAs upper confining layer (outside the active stripe). The oxide provides excellent current confinement for low-threshold laser operation and a low refractive index (n approximately 1.6) for transverse optical confinement and index guiding. Laser diodes with approximately 4-mu-m-wide active regions exhibit 300 K continuous (cw) laser thresholds of 8 mA, with single longitudinal mode operation to 23 mW/facet, and maximum output powers of 45 mW/facet (uncoated). Devices fabricated on a lower confinement AlxGa1-xAs-GaAs QWH crystal (x less than or similar to 0.6 instead of x greater than or similar to 0.8) with approximately 4-mu-m-wide active stripes exhibit 300 K cw thresholds of 9 mA and total external differential quantum efficiencies of 66%. Peak output powers > 80 mW/facet (uncoated) with linear L-I characteristics over the entire operating range are observed. In limited "lifetest" these laser diodes have been operated > 500 h without significant degradation.