Optimization and characteristics of Al-free strained-layer InGaAs/GaInAsP/GaInP SCH-QW lasers (λ~980 nm) grown by gas-source MBE

Aluminum-free strained-layer InGaAs/GaInAsP/GaInP separate-confinement-heterostructure quantum-well lasers emitting at 980 nm have been demonstrated. In particular, optimization of the laser structure and growth conditions using gas-source molecular beam epitaxy have been studied. Closely optimized parameters have been found. The lasers exhibited very good device properties. The lowest threshold current densities obtained for a single-quantum-well laser and three-quantum-well laser were 72 and 150 A/cm², respectively. The internal quantum efficiency was 94%, and the internal waveguide loss was 5.4 cm^-1. The transparency current density and gain coefficient were 33 A/cm² and 0.091-μm/A, respectively. A characteristic temperature ranging from 220 to 280 K was obtained. A ridge waveguide laser exhibited a far-field pattern with a vertical divergence of 47° and a lateral divergence of 13°. These characteristics compare favorably with the best values reported for InGaAs/AlGaAs quantum-well lasers