Abstract: An infrared detector element of the Schottky-barrier type is constructed to have its sensitivity in the range of about 8 to 12 microns. For this purpose a silicon substrate (1) has a highly doped surface layer (3) of p.sup.+ -silicon with a doping density in the range of 5.times.10.sup.18 to 5.times.10.sup.19 (atoms per cm.sup.3) and a thickness in the range of 50 to 200 Angstroms. On top of this layer (3) a metal layer (2) for example of platinum is deposited and partially alloyed into layer (3) to form PtSi. Such elements are arranged in arrays and may be combined with other detector elements having their sensitivity in other spectrum ranges, e.g., 3 to 5 microns and/or in the visible spectrum range.