Analysis of the relation between leakage current and dislocations in GaN-based light-emitting devices

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 (∼2 μm) with higher dislocation density (low × 109 cm–2) prepared by metal-organic vapor-phase epitaxy (sample A), and the other on thick GaN template (∼20 μm) with comparatively low dislocation density (high × 108 cm–2) by hydride vapor-phase epitaxy (sample B). Especially, the template B showed very low value of the dislocation density for a screw component, 2.2 × 107 cm–2 evaluated by transmission electron microscope and 2.3 × 107 cm–2 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 is expected that the screw dislocation were strongly contributed to the leakage current of forward and reverse I-V regions in LEDs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)