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.

Abstract: A semiconductor device in the form of a metal insulator field effect transistor (MISFET) (200) is constructed as a heterostructure of narrow bandgap In.sub.1-x Al.sub.x Sb semiconductor materials. The MISFET (200) is formed from four semiconducting layers (112 to 118) arranged in series as follows: a heavily doped p-type first layer (112), a heavily doped relatively wider bandgap p-type second layer (114), a lightly doped p-type third layer (116) and a heavily doped n-type fourth layer (118). A source (202) and a drain (204) are formed in the fourth layer (118) and a gate (116/205) in the third layer. An n.sup.+ p.sup.- junction (124) is formed between the third and fourth layers and a p.sup.+ p.sup.- junction (122) between the second and third layers. The second layer (114) provides a conduction band potential energy barrier to minority carrier (electron) flow to the gate (116/205), and is sufficiently wide to prevent tunnelling of minority carriers therebetween.

Abstract: A photodetector of semiconductor material includes a photosensitive region adjacent to a minority carrier extraction region arranged when biased to depress the photosensitive region minority carrier concentraction, and means for inhibiting injection of minority carriers to the photosensitive region. Depression of the minority carrier concentration produces low noise and high responsivity properties as obtained by cooling, but without the need for cooling equipment. The minority carrier extraction region may be a pn homo- or heterojunction. Minority carrier injection may be inhibited by a homo- or hetero-structure excluding contact to the photosensitive region, or alternatively by providing the photosensitive region with at least one subsidiary pn junction biasable to inhibit minority carrier flow. The photosensitive region may have an array of extraction regions spaed by less than a minority carrier diffusion length. The extraction regions may have separate outputs to provide respective pixels in a display.

Abstract: A detector, of photosensitive semiconductor material with input and output bias contacts. To improve both frequency response and spatial resolution, minority carriers having tendency to accumulate in the vicinity of the output bias contact are instead rapidly swept out, being driven towards this contact by a concentrated electric field. To produce a local field concentration, the output bias contact may be extended towards the input bias contact, or the detector material near this contact may be configured by slotting or tapering.