Abstract: A method of manufacture of cadmium mercury telluride (CMT) is disclosed. The method involves growing one or more buffer layers on a substrate by molecular beam epitaxy (MBE). Subsequently at least one layer of cadmium mercury telluride, Hg1-xCdxTe where x is between 0 and 1 inclusive, is grown by metal organic vapour phase epitaxy (MOVPE). The use of MBE to grow buffer layers allows a range of substrates to be used for CMT growth. The MBE buffer layers provide the correct orientation for later MOVPE growth of CMT and also prevent chemical contamination of the CMT and attack of the substrate during MOVPE. The method also allows for device processing of the CMT layers to be performed with further MOVPE growth of crystalline CMT layers and/or passivation layers. The invention also relates to new devices formed by the method.

Abstract: This invention relates to the manufacture of Cadmium Mercury Telluride (CMT) on patterned silicon, especially to growth of CMT on silicon substrates bearing integrated circuitry. The method of the invention involves growing CMT in selected growth windows on the silicon substrate by first growing one or more buffer layers by MBE and then growing the CMT by MOVPE. The growth windows may be defined by masking the area outside of the growth windows. Growth within the growth windows is crystalline whereas any growth outside the growth windows is polycrystalline and can be removed by etching. The invention offers a method of growing CMT structures directly on integrated circuits removing the need for hybridisation.

Abstract: An infra-red detector (10) comprises a detector region (38) and a collector region separated by a barrier region. Operation of these regions is controlled by potentials applied to respective gate electrodes (30, 34, 32), insulated from the detector, barrier and collector regions by an insulating oxide layer (36). The detector, barrier, and collector regions may be arranged on a silicon substrate (24). In operation, photo-excited electrons are generated in the detector region and these cross the barrier region for readout from the collector region.

Abstract: A noise reduced photon detector incorporates an array (10) of semiconductor diode detector elements (12). Each element (12) has an extrinsic active layer (20) sandwiched between two layers (18, 22) of wider bandgap and mutually opposite conductivity type. These layers are in turn sandwiched between two further layers (16, 24) of wider bandgap than the active layer (20) and of higher doping than the other layers (18, 22). A mirror (34) extends round much the array (10) and isolates each element (12) from photons emitted by other elements (12). In operation the elements (12) are reverse biased and exhibit negative luminescence which reduces their photon emission. These two effects reduce unwanted photon generation and absorption, and consequently photon noise is also reduced.

Abstract: A thermal imaging system (10) which is accoupled and by scanning recreates a thermal image by superimposing measured variations in infrared emission from a scene (22) onto a reference level supplied by a light emitting diode (28). The diode (28) is both a positive and negative luminescent emitter. Emitted flux is current controlled to be equivalent to black body radiation at a range of temperatures which may be colder or hotter than ambient. A signal generated with the system (10) switches between scene and diode observation is a measure of the difference between the mean scene temperature and the diode effective temperature. In response to this digital, control means adjust the bias current through the diode (28) in order to reduce the temperature difference. The reference temperature converges towards the mean scene temperature as this process is repeated. Absolute temperature is thus restored and some image defects removed.

Abstract: A thermal sensing system (10) including an array of photon detectors (14) produces a detector-dependent response to irradiation. Variations in individual detector characteristics produce a fixed pattern noise which degrades an image or other response. A switchable mirror (M1) may at one position (P.sub.cal) direct infrared radiation from a light emitting diode (20) onto the detector array (14). The diode (20) is both a negative and positive luminescent emitter, the flux emitted is current controlled to be equivalent to black body radiation at a range of temperatures both colder and hotter than ambient. Calibration relationships comprising transfer functions relating incident intensity to signal response are derived for each detector. Alternatively the mirror (M1) may be at an observation position (P.sub.obs) and infrared radiation from a remote scene reaches the detector array (14).

Abstract: A dynamic infrared scene projector for use infrared detections systems which has particular, although not exclusive, use in thermal imaging or seeker systems. In such systems, a dynamic infrared scene projector is used to simulate the thermal scene for testing and calibration purposes. The device comprises an array of electroluminescent semiconductor diode structures, capable of emitting both positiveand negative luminescence, and electronic circuitry for supplying currents of both polarity to each diode independently so that the emission of positive and negative luminescence can be controlled. The diode structures in the array are based on narrow bandgap semiconductor materials, for example, the Hg.sub.1-x Cd.sub.x Te, In.sub.1-x Al.sub.x Sb, Hg.sub.1-x Zn.sub.x Te or In.sub.1-x Tl.sub.x Sb materials systems (where x is the composition). In a preferred embodiment, the diodes are capable of emitting infrared radiation in the wavelength regions between 3-5 .mu.m or 8-13 .mu.m.