Dislocation related issues in the degradation of GaN-based laser diodes

• Published in: IEEE journal of selected topics in quantum electronics Vol. 10; no. 6; pp. 1277 - 1286
• Main Authors: Tomiya, S., Hino, T., Goto, S., Takeya, M., Ikeda, M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-11-2004; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aging; Cathodoluminescence microscopy; cross slip; Degradation; diffusion; Diode lasers; dislocation; dislocation climb; dislocation glide; Energy consumption; epitaxial lateral overgrowth (ELO); Gallium nitride; GaN; laser diode; Light emitting diodes; magnesium; Radiative recombination; recombination-enhancement effect; reliability; Semiconductor materials; Studies; Substrates; Transmission electron microscopy
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2004.837735

We investigate degraded GaN-based laser diodes (LDs) on epitaxial lateral overgrown GaN layers in terms of dislocations. Almost all of the threading dislocations that appear in the wing regions are a-type dislocations. Their origins are the lateral extension of dislocations from the seed regions that contingently bend upwards to the episurface. Comparing short-lived LDs and long-lived LDs that have almost the same power consumption, we find that the relative levels of dislocation densities in their respective active layers are different. In the degraded LDs, neither dislocation multiplication from the threading dislocations nor any structural changes of the threading dislocations are observed. This indicates that degradation is not caused by dislocation multiplication at the active layers, which is usually observed in LDs featuring zincblende-based structures. The degradation rate is almost proportional to the square root of the aging time. Our results indicate that degradation is governed by a diffusion process, and a detailed degradation mechanism is proposed.