Abstract: Compact electrical connections (4) are formed on side-walls (1) of an infrared detector element having a step structure (1 to 3) over which a conductive layer (40) is deposited. Using a directional etching treatment, such as ion milling, the conductive layer (40) is removed from at least the bottom (3) of the step structure but is left lining the side-wall (1) as the connection (4). This permits formation of connections (4 and 44) in compact dense arrays, including plural-wavelength arrays in stacked bodies (10 and 20) on a circuit substrate (30).

Abstract: At least one detector element (1) of cadmium mercury telluride or other infrared-sensitive semiconductor material is sandwiched between a substrate (20) and a lens plate (10) or other optical element. When an adhesive layer (11) is used to secure the lens plate or substrate over the detector element (1), there is found to be an unexpected decrease in cut-off wavelength and increase in junction resistance. In experiments leading to the invention, these changed characteristics were found to result from stress induced in the semiconductor material (1) by contraction of the adhesive (11) which led to a change in the energy bandgap of the semiconductor material (1). The stress is reduced and changes in characteristics minimised by adopting a slotted layer structure 1 and 8, in which the element body (1) is part of a wider layer (1 and 8) of the semiconductor material which occupies a majority of the volume around the element body (1) between the substrate (20) and the optical element (10).