U.S. Philips Corporation

William A Dunn

Ian M Baker

Patrick J Ball

David J Gowlett

An infrared detector device for at least two wavelengths, i.e. 3 to 5 microns and 8 to 14 microns, comprises detector elements (10 and 20) formed in two or more infrared-sensitive materials with different badgaps, e.g. in cadmium mercury telluride. These materials may be provided side-by-side in a single level on a substrate (3) or preferably as different levels (1 and 2) on the substrate (3). Each detector element (10 and 20) comprises a p-n junction (11 and 21) between opposite conductivity type regions (12,13 and 22,23). Electrical connections (15,25,24) extend from these regions to the substrate (3). Freedom in design and fabrication is obtained by a connection structure in which one connection (25) of the longer-wavelength response element (20) contacts both the semiconductor material (2) of that element (20) and the larger-bandgap material (1) of the shorter-wavelength response element (10), at a side-wall (42) of both materials. The larger-bandgap material (1) comprises a further region (18) which adjoins the side-wall (42) and which forms a further p-n junction (19) electrically in parallel with the p-n junction (21) of the longer-wavelength detector element (20).

Plural-wavelength infrared detector devices

An infrared detector has an infrared detector element (2) mounted at a first part (11) of a housing (1), a Joule-Thomson cooling element (3) accommodated in a second part (12), and an infrared transmissive window (15) at the front of the housing (1). A compact, space-saving and light weight structure with improved optical efficiency is obtained. The core of the Joule-Thomson cooling element (3) forms a third part (13) of the housing (1), and these second and third parts (12 and 13) of the housing extend towards the front of the detector. The cooler core (13) which may carry a cooled filter (25) has a hollow shape or is otherwise infrared transmissive in front of the detector element (2) and can direct incident radiation (50) towards the detector element (2). For this purpose the inner surface of the hollow core (13) may carry a reflective conductor pattern (18,19) which also provides electrical connections for the detector element (2). This core part (13) may seal a channel in a grooved intermediate member (48 in FIG. 3) between the second and third housing parts (12 and 13) so as to form the Joule-Thomson cooling element (3) without requiring conventional finned metal tubing (31 in FIG. 1).

Infrared detectors

An infra-red radiation detector comprises an envelope in the form of a dewar (1,2) in which a vacuum space (12) is present between an outer wall (2) and inner wall (1) cooled by a cooling element (20). Gas molecules are gettered from the vacuum space (12) by at least one shaped molecular-sorbent porous body (10,10') having a major surface which fits onto and is bonded to a cooled surface (e.g. of a radiation shield 8) associated with the cooled inner wall (1). The shaped getter body (10,10') is secured (e.g. by epoxy adhesive) at its major surface to this cooled surface in a heat-exchange relationship so as to be cooled by the cooling element (20) during operation of the detector. The shaped getter body (10,10') is preferably a moulded annulus of synthetic zeolite material.

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Nomanshand, United Kingdom

William A Dunn