Our group has developed the first 1024x1024 high background Si:As detector array, the Megapixel Mid-Infrared array (MegaMIR). MegaMIR is designed to meet the thermal imaging and spectroscopic needs of the ground-based and airborne astronomical communities. MegaMIR was designed with switchable capacitance and windowing capability to allow maximum flexibility. We report initial test results for the new array.