Structural and Elastic Properties of α-(AlxGa1−x)2O3 Thin Films on (11.0) Al2O3 Substrates for the Entire Composition Range

Abstract

Structural properties of rhombohedral α-(AlxGa1−x)2O3 thin films grown by two combinatorial pulsed laser deposition (PLD) techniques are investigated for the entire composition range. One α-(AlxGa1−x)2O3 thin film is deposited on a 2 inch in diameter large a-plane sapphire substrate using the continuous composition spread (CCS) PLD technique to fabricate a thin film with varying Al content ranging between x = 0.13 and x = 0.84. Laterally homogeneous α-(AlxGa1−x)2O3 thin films exhibiting discrete Al contents are fabricated using radially segmented PLD targets on (11.0) Al2O3. Independent of the PLD technique, for x ≈ 0.55, a change from relaxed to pseudomorphic growth is observed as confirmed by the evolution of in- and out-of-plane lattice constants. The crystal structure is studied depending on the cation composition by X-ray diffraction confirming the fabrication of epitaxial, corundum-structured thin films.