Lawrence Berkeley National Laboratory

Conventional and high resolution electron microscopy have been applied for studying lattice defects in nonpolar a-plane GaN grown on a 4H-SiC substrate with an AlN buffer layer. Samples in plan-view and cross-section configurations have been investigated. Basal and prismatic stacking faults together with Frank and Shockley partial dislocations were found to be the main defects in the GaN layers. High resolution electron microscopy in combination with image simulation supported Drum s model for the prismatic stacking faults. The density of basal stacking faults was measured to be ~;1.6_106cm-1. The densities of partial dislocations terminating I1 and I2 types of intrinsic basal stacking faults were ~;4.0_1010cm-2 and ~;0.4_1010cm-2, respectively. The energy of the I2 stacking fault in GaN was estimated to be (40+-4) erg/cm2 based on the separation of Shockley partial dislocations. To the best of our knowledge, the theoretically predicted I3 basal stacking fault in GaN was observed experimentally for the first time.