Degradation mechanisms of Ga1−xAlxAs visible diode lasers

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Abstract
Degradation of Ga1−xAlxAs visible diode lasers in the 0.7‐μm wavelength region is investigated through room‐temperature life tests. A marked dependence of laser life on lasing wavelength is observed. In particular, degradation proceeds faster for shorter‐wavelength lasers. It is shown that the degradation of lasers radiating at wavelengths below 730 nm can mainly be attributed to the rapid formation of dark regions and dark‐line defects during aging. A notable improvement in life is obtained for these shorter‐wavelength lasers by Te doping of the active layer. On the other hand, degradation at above 740 nm results from enhanced facet oxidation due to high AlAs mole fractions in the active and cladding layers. This facet oxidation is effectively suppressed by facet coatings with SiO2 films. As a result, stable operations, exceeding 4000 h, are achieved in the 740–770‐nm wavelength region.