IMPROVED RED AND INFRARED LIGHT EMITTING AlxGa1−xAs LASER DIODES USING THE CLOSE-CONFINEMENT STRUCTURE

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Abstract
AlxGa1−xAs injection lasers have been fabricated over the compositional range in which the alloy has a direct bandgap transition (0 < x ≤ 0.34). At 300°K the threshold current density increases with x from 12 000 A/cm2 (λL = 8600 Å) to 56 000 A/cm2 (λL = 7340 Å) in uncoated devices with cavity lengths of about 10 mils. In the same range of x the external differential quantum efficiency gradually decreases from 40 to 16%. These are the highest efficiencies and lowest threshold current densities ever reported for room‐temperature lasers emitting in the same spectral range. The improvement is due to utilization of the new p+‐p heterojunction structure previously used by the authors in GaAs lasers to sharply reduce the internal optical loss by improving the optical confinement and reducing the absorption coefficient in the p+ material adjoining the active region. At 77°K lasing has been achieved to 6450 Å and cw operation to 6900 Å with the emission of 0.4 W per diode.