The effects of the threading dislocations on the qualities in undoped GaN

We investigated the effects of growth rate during the growth of GaN buffer layer on the GaN epilayer. It was found that the growth rate of the GaN buffer layer plays a key role in improving the quality of GaN film on a sapphire and optimum growth rate is in existence to show best crystal quality. The improvements obtained from changing buffer growth rate are explained by the promotion of lateral growth mode under optimum buffer growth rate. Besides, We have observed edge dislocations among several threading dislocation components existing in GaN epilayer are related with the reduction of electron Hall mobility and optical luminescence efficiency.