Epitaxial Si and Gd2O3 Heterostructures: Distributed Bragg Reflectors with Stress Management Function for GaN on Si Light Emitting Devices

Abstract

Tensile stress in GaN layers grown directly on Si is a serious obstacle for the implementation of this technology for electronic and photonic devices. The problem can be solved by stress engineering using epitaxial buffer layers grown on a Si-substrate. Heteroepitaxial Si and Gd2O3 multilayer structures that can be used both as a tensile strain compensating buffer for GaN epitaxial layers and an efficient reflector for light emitting devices are demonstrated in this work. A three-period distributed Bragg reflector has been fabricated. It exhibits 82% reflectivity at the design wavelength of 450 nm. In situ curvature measurements of the 200 mm diameter wafers with the grown structure reveal compressive stress in the Gd2O3 – Si multilayer structure. The compressive stress compensates the tensile stress which arises during subsequent growth and cooling of the GaN layer.