The Secretary of State for Defence in Her Britannic Majesty's Government

Robin F Farrow

Anthony M White

Anthony B Dean

Gordon Robert Jones

Philip W Sullivan

Piero Migliorato

Gerald M Williams

A photo diode formed by a substrate of Cd.sub.x Hg.sub.1-x Te covered with a layer of CdTe forming a p-n junction. The substrate may be p-type in which case the layer is n-type or vice versa. An array of photo diodes may be formed by covering the substrate with semi-insulating CdTe and forming islets of In on the CdTe. Heating causes In to diffuse into the CdTe doping it n-type. This results in regions of n-type CdTe surrounded by semi-insulating CdTe each region forming, with the substrate, a photo diode. The heating also causes diffusion between the Cd.sub.x Hg.sub.1-x Te and CdTe to give a graded heterostructure. Electrical connections are made to the substrate, and each n-type region. The n-type CdTe region may alternatively be formed by molecular beam epitaxial growth techniques using a beam of In dopant.

Infrared sensitive photo diode

An FET device comprises a substrate with source and drain regions separated by a gate structure. Between the gate and substrate is an insulator formed of a cubic fluorite structure material that is lattice matched within 1% to the substrate. The insulator may be a group II fluoride such as Ca.sub.y Cd.sub.1-y F.sub.2 (0.ltoreq.y.ltoreq.1), Sr.sub.z Ba.sub.1-z F.sub.2 (0.ltoreq.z.ltoreq.1), or Ba.sub.x Ca.sub.1-x F.sub.2 (0.ltoreq.x.ltoreq.1), or an oxide such as CeO.sub.2, PbO.sub.2. The substrate may be a bulk semiconductor or an epitaxial layer such as Si, InP, GaAs, Ga.sub.x Al.sub.1-x As, GaSb, InAs, or AlAs.

Field effect transistor with gate insulation of cubic fluoride material

Group III-V compound substrates are heat cleaned under vacuum conditions by heating above their congruent temperature and subjecting the substrate to at least one molecular beam of the material preferentially evaporating from the substrate thereby maintaining surface stoichiometry. Surfaces so cleaned may then have an epitaxial layer grown thereon under similiar conditions from molecular beams. Alternatively the cleaned surface may be coated with cesium and oxygen to form a photocathode.

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Malvern, United Kingdom

Robin F Farrow