Methods of forming optoelectronic devices include forming an electrically conductive layer on a first surface of a substrate and forming a mirror backing layer from the electrically conductive layer by forming an endless groove that extends through the electrically conductive layer. A step is then performed to remove a portion of the substrate at a second surface thereof, which extends opposite the first surface. This step exposes a front surface of the mirror backing layer. An optically reflective mirror surface is then formed on the front surface of the mirror backing layer.