Dislocations in GaN-based laser diodes on epitaxial lateral overgrown GaN layers were investigated by using transmission electron microscopy and cathodoluminescence microscopy. A correlation was found between dislocations and device reliability. The dislocation density in the seed regions of epitaxial laterally overgrown GaN layers was of the order of 108/cm2, while that in the wing regions was less than mid-106/cm2. At the origin of dislocations in the wing regions was the extension of defects in highly defective regions near to the GaN layer/substrate interface in the seed regions. It was noted that some laser diodes had a shorter lifetime, although their power consumption was almost the same. It was found that, in laser diodes with short lifetimes, dislocations lying in the c-plane were formed below the active regions, bent towards the c-axis and threaded upwards to active regions. These newly-created dislocations could be detrimental to device lifetime.

Dislocations in GaN-Based Laser Diodes on Epitaxial Lateral Overgrown GaN Layers. S.Tomiya, H.Nakajima, K.Funato, T.Miyajima, K.Kobayashi, T.Hino, S.Kijima, T.Asano, M.Ikeda: Physica Status Solidi A, 2001, 188[1], 69-72