Abstract: A method for making and using a group IV-VI photovoltaic semiconductor diode such that its capacitance is reduced substantially with respect to its capacitance if made and used according to prior art techniques. The capacitance reduction may be obtained without detrimental effect to the detectivity and noise levels of the diode. In the currently preferred form of the method, a thin film of p conductivity type semiconductor material, PbTe, is applied to (epitaxially grown on) a cleaved BaF.sub.2 substrate. A layer of Pb is deposited on the semiconductor material to form a diode having an n+ conductivity type region in the semiconductor material and a depletion region. When the PbTe semiconductor material is applied to the BaF.sub.2 substrate, its thickness is limited such that the depletion region extends to the boundary formed between the PbTe and BaF.sub.