Polytypes in GaN films grown by metalorganic chemical vapor deposition on (0 0 0 1) sapphire substrate

Microstructural observations on cubic zinc blende (ZB) GaN structure in hexagonal wurtzite (WZ) GaN films grown by metalorganic chemical vapor deposition (MOCVD) on (0 0 0 1) sapphire substrate were carried out using high resolution transmission electron microscopy (HRTEM) working at 300 kV. A microdomain of the ZB GaN polytype has been found in a region 35 nm away from the interface of WZ GaN/sapphire. The (1 1 1) plane of ZB GaN lies parallel to (0 0 0 1) WZ GaN plane. The height of the microdomain was 0.8 nm and its width was 9 nm. The observed images of both ZB and WZ GaN structures are in good agreement with those obtained by computer simulations. (C) 1998 Elsevier Science B.V. All rights reserved.