New phenomena on misfit dislocations in a GaAlAsP-GaAs heterojunction under light irradiation

A Ga0.92Al0.08As-Ga0.7Al0.3As0.991P0.009T-Q double-heterostructure (DH) laser has been operating for over 7000 hours at 70°C. Its optical power from one facet is 4 mW. The degraded T-Q DH laser has been studied by photoluminescence (PL) topography. Dark-line defects in the and directions have been observed in the active layer of the degraded laser. The dark-line defects in the direction originate from the dark-line defects in the direction. The dark-line defects in the direction are attributable to the misfit dislocations introduced during liquid-phase-epitaxial (LPE) growth. The misfit dislocations are found, by PL topography, to be formed at the interface between the GaAs buffer layer and the quaternary-clad layer. These results indicate that the misfit dislocation in the direction moves to the active layer from the interface between the GaAS buffer layer and the quaternary-clad layer during laser operation. Degradation of the T-Q DH laser is associated with the light-induced motion of the misfit dislocation. Light-induced motion of the misfit dislocation has been also observed in the T-Q DH wafer.