EXPERIMENTAL GAIN CHARACTERISTICS AND BARRIER LASING IN STRAINED-LAYER INGAAS-GAAS-ALGAAS QUANTUM-WELL HETEROSTRUCTURE LASERS

Gain characteristics are reported for a series of five separate confinement heterostructure InxGa1-xAs-GaAs-Al0.20Ga0.80As (0.08 < x < 0.33) strained-layer quantum well lasers with a 70 angstrom well thickness. The differential current gain beta increases with indium composition from 14.2 for x=0.16 to 27.4 cm/A for x=0.33, as calculated from a semilogarithmic gain-current density relation. Data are also presented on emission wavelengths and threshold current as a function of composition and cavity length. Devices with x=0.08 are unable to reach threshold on the quantum well transition, and laser operation in the barriers is observed for all cavity lengths. Devices with higher indium fraction switch from the n = 1 transition in the quantum well for long cavity lengths to the n=2 transition and to the GaAs barriers for short cavities due to saturation of the available quantum well gain.