Structural TEM study of nonpolar a-plane gallium nitride grown on (1120) 4H-SiC by organometallic vapor phase epitaxy
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-sectional 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 similar to 1.6x10(6) cm(-1). The densities of partial dislocations terminating I-1 and I-2 types of intrinsic basal stacking faults were similar to 4.0x10(10) cm(-2) and similar to 0.4x10(10) cm(-2), respectively. The energy of the I-2 stacking fault in GaN was estimated to be (40 +/- 4) erg/cm(2) based on the separation of Shockley partial dislocations.