TEM observation in cross section of defects in a long-term-degraded Ga1−xAlxAs double-heterostructure injection laser diode

A degraded Ga1−xAlxAs double-heterostructure injection cw laser diode with a lifetime of 1070 h was examined in cross section by TEM. The device contains defects whose contrast is identical to that produced by coherent or partially coherent precipitates and/or by prismatic dislocation loops. They have not previously been observed either in undegraded Ge- or Sn-doped material or in devices degraded by DLD formation. These defects were observed in the top p (Ge) -GaAs layer as well as in the p (Ge) -Ga1−xAlxAs layer adjacent to it. There is a tendency for these defects to decorate the interface between these two layers as well as the interface between the active region and the p (Ge) -Ga1−xAlxAs layer. Furthermore, these defects seem to cluster in regions adjacent and above these two interfaces. These defects have not, however, been observed in the active, the n- (Sn) -Ga1−xAlxAs, and the n-GaAs substrate regions.