Novel growth technique for the reducing dislocation density in GaN on sapphire substrate

Abstract

The selective lateral growth of GaN with extremely low dislocation density has been achieved for the first time directly on a masked sapphire substrate without a GaN epitaxial underlayer via metalorganic vapor phase epitaxy. Both the mask material for selective growth and the growth conditions have been optimized for this complete selective growth. Dislocation densities less than 5 × 106 cm-2 have been obtained when SiN was used as a mask and GaN was used as a low-temperature buffer layer. This reduction in threading dislocation density results from bending the threading dislocations toward the facet surfaces, which has been confirmed by cross-sectional transmission electron microscopy observations. This growth technique is very promising for practical device production, such as that for blue laser diodes, because a complete device structure with extremely low dislocation density can be grown by a single growth process. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.