The Post Office

British Telecommunications Corporation

John Haigh

Marc M Faktor

Rodney H Moss

Martin R Aylett

Materials whose elemental constituents are selected from groups III and V of the Periodic Table are photochemically etched in a reducing environment. Etching is carried out by illuminating a halogenated hydrocarbon gas, e.g. methyl iodide, with ultra-violet light in the vicinity of the material. The reducing environment is provided by the presence of sufficient hydrogen to suppress the effect of any oxygen leaking into the system. Methods according to the invention may be used in particular in the production of opto-electronic devices.

Etching method

A Group III element Q selected from gallium, indium and thallium containing a Group VI element X selected from oxygen, sulphur, selenium and tellurium as an impurity can be purified by adding, to molten Q, an element M capable of forming with X a stable solid compound substantially insoluble in liquid Q. The stable solid compound can be separated and the purified Q used in the epitaxial growth of a semiconductor material such as indium phosphide. Alternatively, in a process for the epitaxial growth of a semiconductor compound of Q in molten Q, X can be removed in situ by the addition of a suitable element of the M-type.

Semiconductor materials

Semiconductor compounds which are alloys of group III-V compounds are grown by a liquid phase epitaxy method which includes heating growth apparatus in a reducing atmosphere while maintaining a solvent for the compound, a source of the group III-V compound and another element of the alloy separate from each other. After heating to reduce oxides, the element is added to the solvent, the source is brought into contact with the solvent and the resulting solution is brought into contact with a substrate to effect growth of the compound. Apparatus for carrying out the method is also described.

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Ipswich, United Kingdom

John Haigh