Benefits and limitations of unipolar barriers in infrared photodetectors

When properly employed, unipolar barriers can significantly improve the performance of infrared photodetectors; however, the barriers must be correctly engineered and properly located in the epitaxial structure in order for detectors to function optimally. Unipolar barrier concepts, design, and implementation in several device architectures are discussed. nBn and unipolar barrier photodiodes are demonstrated in the InAs materials system, and the limitations of unipolar barriers are considered.