DEGRADATION MECHANISM OF GAAS ALGAAS QUANTUM-WELL LASER

The problem of increasing the lifetime of GaAs/AlGaAs double heterostructure (DHS) laser stimulated a wide range of publications concerning with the study of degradation processes.1-6 On the whole, at present a certain understanding of the problem has been achieved. It was shown in Refs. 1-3 that the processes of recombination-enhanced dislocation climb (REDC) and recombination-enhanced dislocation glide (REDG) may dominate in the rapid degradation phenomenon. Dislocation climb requires the motion of intrinsic point defects, while the dislocation glide occurs mainly due to local stress or local heating as a result of nonradiative recombination. The role and the origin of point defects which participate in the dislocation climb process is not understood yet. There are two models of defect generation: extrinsic and intrinsic.1.3 The first model assumes that V(Ga) and V(As) are produced in the dislocation core at an equal rate during REDC. The second model requires the absorption of existing point defects (As interstitials) at a dislocation and the generation of antisite defects As(Ga), Ga(As), V(Ga) during REDC of dislocation. A heterointerface may be probably viewed as a source of large concentration point defects. 2,7,8 Interface defects may be generated due to a local stoichiometry variation during the growth of a heteroepitaxial layer.2.7 The processes of heterostructure laser degradation are usually investigated by transmission and scanning electron microscopy techniques. Dark line defects (DLD), which form at a rapid laser degradation and which are the centers of nonradiative recombination, are observed by an electron probe induced current technique.