British Telecommunications Public Limited Company

Michael J Harlow

Paul C Spurdens

Michael J Robertson

David Graham Moodie

Ian F Lealman

Andrew W Nelson

Simon Cole

Mark A Salter

David J Newson

Stanley Y Wong

William James Duncan

An indium phosphate semiconductor substrate is prepared for subsequent growth of epitaxial layers to form a semiconductor device. In the preparation, the substrate is first annealed to promote any tendency for surface accumulation of impurity atoms by diffusion from the substrate and to promote impurity atom removal from the surface of the substrate. The substrate is then surface etched to remove further impurities and to provide a clean, flat surface for subsequent epitaxial layer growth. The final stage of preparation involves growing a semi-insulating buffer layer on the substrate to isolate the device epitaxial layers from the substrate.

Preparation of semiconductor substrates

Discrete electroabsorption modulator

Electrical barrier structure for semiconductor device doped with

It has been found that layers which include arsenic and/or zinc can have an adverse effect upon optoelectronic semiconductor devices such as lasers. This is reduced by treatments in which arsenic and zinc are excluded. Preferably the substrate is cooled from reaction temperature in the presence of a mixture of hydrogen and PH.sub.3 (replacing AsH.sub.3 and/or Zn(CH.sub.3).sub.2 used to grow the final layer). Alternatively, devices have a contact layer of heavily p-type gallium indium arsenide are improved by the deposition of a protective layer of indium phosphide. This layer is removed immediately before metalization. Even though the protective layer is not present in the final product it has a beneficial effect.

Preparation of semiconductor devices

Growing community of inventors

Ipswich, United Kingdom

Michael J Harlow