Growth and properties of GaAsSb/GaAIAsSb double heterostructure lasers

The growth and properties of GaAs 1-x Sb x /Ga 1-y Al y As 1-x Sb x double-heterostructure (d.h.s.) lasers have been investigated. We have obtained lasers with an antimony content up to x = 0.17 emitting at wavelengths up to 1.12 μm at room temperature for pulsed currents as low as 120 mA. The d.h.s.s were grown by liquid-phase epitaxy on GaAs substrates. The lattice mismatch problem was overcome by growing up to ten ternary GaAs 1-x Sb x layers of graded Sb composition. A study of quaternary GaAlAsSb layer growth has shown the effect of initial saturation of the melt on the Al content of the resulting solid. To overcome this problem a special epitaxial process has been developed to grow quaternary layers with controlled aluminium content. The relative amounts of Al and Sb were determined by a photoluminescence technique which also allowed us to evaluate the band-gap energy step between the active and confinement layers. A study of the temperature dependence of the threshold current was also made for d.h.s having different aluminium compositions. Threshold current density was found to vary as exp T/T o , where T o reaches 150 K for the highest aluminium content.