The microstructural properties of AIN layers grown on a Si(111) substrate were studied in detail using transmission electron microscope techniques to determine phase transition behaviors. AIN layers were grown in the wurtzite (WZ) and zinc-blende (ZB) polytypes. The dominant phase of AIN was transformed from a ZB structure to a WZ structure as the substrate temperature increased. Many protrusions were observed on the surfaces of AIN layers, and their density was decreased with an increase in the substrate temperature; these protrusions originated from the WZ structure of AIN and not the ZB structure. In our experiment, WZ-AIN grains were frequently observed at the edge and/or on the surface of the ZB-AIN grains at relatively low substrate temperatures. The preferred crystallographic orientation relationships of the {111}(ZB-AIN)parallel to{111}(si) and <1<(1)over bar>0>(ZB-AIN)parallel to<1<(1)over bar>0>(si) between the ZB-AIN and the Si substrate and the (0001)(WZ-AIN)parallel to(111)(si) and [(1) over bar2 (1) over bar0](WZ-AIN)//[1 (1) over bar()0](si) between WZ-AIN and the Si substrate were identified in our experiment. (C) 2011 Elsevier B.V. All rights reserved .