The influence of substrate atomic step morphology on threading dislocation distributions in iii-nitride films

In this study, we investigated the influence of atomic step morphologies of 4H-SiC surfaces on the distribution of threading edge and screw dislocations in GaN films grown by MOCVD. Electron channeling contrast imaging (ECCI) was implemented to profile engineered 4H-SiC mesas. Two types of atomic morphologies were consistently observed at these mesa surfaces. Mesa surfaces with no screw dislocations exhibited purely atomic step-free surfaces except within 2-20 mum of the mesa edges. Mesas penetrated by at least one screw dislocation exhibited a uniform though highly stepped atomic surface across the entire mesa.