Phase separation of thick (∼1 µm) InxGa1−xN (x ∼ 0.3) grown on AlN/Si(111): Simultaneous emergence of metallic In-Ga and GaN-rich InGaN

0.3-2-µm-thick InxGa1−xN (x ∼ 0.3) films are grown at 650 °C on AlN/Si(111) substrates by metal organic vapor phase epitaxy. When the thickness of an epitaxial InGaN film exceeds ∼1 µm, peaks of GaN-rich InGaN(0002) and metallic In(101) appear in the X-ray diffraction profiles. The InN composition ∼0.03 in the GaN-rich InGaN film is in agreement with the solubility of InN in GaN at 650 °C. The metallic In contains a small amount (∼0.03 at. %) of Ga. These results clearly show that the epitaxial InGaN film is phase-separated into GaN-rich and InN-rich InGaN. The latter is changed into metallic In-Ga owing to its thermal instability at 650 °C.