In order to understand the origin of leakage current, light emitting devices were grown on two different templates with apparently different dislocation density: one on thin GaN template (~2μm) with higher dislocation density (low x 109/cm2) prepared by metal-organic vapour-phase epitaxy (sample A), and the other on thick GaN template (~20μm) with comparatively low dislocation density (high x 108/cm2) by hydride vapour-phase epitaxy (sample B). Especially, the template B showed very low value of the dislocation density for a screw component, 2.2 x 107/cm2 evaluated by transmission electron microscope and 2.3 x 107/cm2 approximated by the Williamson-Hall plot which was evaluated by high-resolution X-ray diffraction, respectively. On the other hand, sample A showed one order higher, low × 108 cm-2, than that of sample B for a screw component. Sample A showed the larger leakage current (more than two orders of magnitude) than sample B in a forward-biased region and a reverse-biased region also. It was expected that the screw dislocation were strongly contributed to the leakage current of forward and reverse current-voltage regions in LEDs.

Analysis of the Relation between Leakage Current and Dislocations in GaN-Based Light-Emitting Devices. S.W.Lee, D.C.Oh, H.Goto, J.S.Ha, H.J.Lee, T.Hanada, M.W.Cho, S.K.Hong, H.Y.Lee, S.R.Cho, J.W.Choi, J.H.Choi, J.H.Jang, J.E.Shin, J.S.Lee, T.Yao: Physica Status Solidi C, 2007, 4[1], 37-40