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

Abstract

A Ga 0.92 Al 0.08 As-Ga 0.7 Al 0.3 As 0.991 P 0.009 T-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 \langle100\rangle and \langle1\bar{1}0\rangle directions have been observed in the active layer of the degraded laser. The dark-line defects in the \langle100\rangle direction originate from the dark-line defects in the \langle1\bar{1}0\rangle direction. The dark-line defects in the \langle1\bar{1}0\rangle 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 \langle1\bar{1}0\rangle 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.