Heteroepitaxial IV–VI infrared sensors on Si-substrates with fluoride buffer layers

Abstract

Epitaxial layers of IV–VI narrow gap semiconductors (PbTe, PbSe, PbSnSe) have been grown onto Si-wafers with the aid of graded epitaxial CaF 2-BaF 2 buffer films by molecular beam epitaxy (MBE). Photovoltaic IR sensors for the 3–5 μm and 8–12 μm range have been fabricated in these structures. They exhibit near background noise limited sensitivity (for room temperature radiation) at their operating temperature of about 77 K. The results open up the possibility to construct large heteroepitaxial monolithic integrated circuits, e.g. staring IR focal plane arrays for thermal imaging applications: IR sensors are integrated in the narrow gap semiconductor layer and the Si-substrate is used for signal processing circuitry. Furthermore, the graded fluoride buffer technique offers more general applicability for the growth of heteroepitaxial stacks of different nonlattice matched semiconductor materials. Future integrated circuits and sensors fabricated in such stacks on a common substrate will combine and take advantage of the different properties of the different materials.