Highly luminescent, high-indium-content InGaN film with uniform composition and full misfit-strain relaxation

We have studied the properties of thick In_xGa_1-xN films, with indium content ranging from x ∼ 0.22 to 0.67, grown by metal-modulated epitaxy. While the low indium-content films exhibit high density of stacking faults and dislocations, a significant improvement in the crystalline quality and optical properties has been observed starting at x ∼ 0.6. Surprisingly, the In_xGa_1-xN film with x ∼ 0.67 exhibits high luminescence intensity, low defect density, and uniform full lattice-mismatch strain relaxation. The efficient strain relaxation is shown to be due to a critical thickness close to the monolayer range. These films were grown at low temperatures (∼400 °C) to facilitate indium incorporation and with precursor modulation to enhance surface morphology and metal adlayer diffusion. These findings should contribute to the development of growth techniques for nitride semiconductors under high lattice misfit conditions.