The origin of the dislocation climb which takes place in the presence of electron-hole recombination in laser structuresis discussed. TEM studies on lasers which have been degraded by either forward bias or by optical pumping show that the climb dipoles are extrinsic in both cases. In addition, completely isolated interstitial loops can form which also have the characteristic climb appearance of the larger dipoles. Existing theories for the origin of the interstitials required to account for the observed climb are considered in detail, and it is concluded that the climb structures can best be explained by the emission of both gallium and arsenic vacancies from the dislocation as a consequence of nonradiative processes occurring at the dislocation core.

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Transmission electron microscopy has been used to study the defects associated with the degradation of broad−contact geometry double−heterostructure lasers. Two different types of dislocation networks have been observed close to the active region of the degraded device having Burgers vectors of (a/2) 〈011〉 and a〈001〉. Both networks have been shown to be of interstitial character.

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