Structural study of GaN grown on (001) GaAs by organometallic vapor phase epitaxy

Detailed transmission electron microscope (TEM) and transmission electron d iffraction (TED) examination has been performed on organometallic vapor pha se epitaxial GaN layers grown on (001) GaAs substrate to investigate micros tructures and phase stability. TED and TEM results exhibit the occurrence o f a mixed phase of GaN. The wurtzite (alpha) phase grains are embedded in t he zinc-blende (beta) phase matrix. It is shown that there are two types of the wurtzite GaN phase, namely, the epitaxial wurtzite and the tilted wurt zite. The tilted wurtzite grains are rotated some degrees ranging from simi lar to 5 degrees to similar to 35 degrees regarding the GaAs substrate. A s imple model is presented to describe the occurrence of the mixed phases and the two types of the wurtzite phase.