Northern Telecom Limited

Bookham Technology Limited

Canadian Patents and Development Limited/societe Canadienne Des Brevets

Cornelis Blaauw

Grzegorz Pakulski

Hussein M Naguib

Agnes Margittai

D Gordon Knight

Ahmad Aftab

Ronald Moore

Syed M Ahmed

A semiconductor device such as a buried heterostructure semiconductor laser includes a semiconductor substrate supporting an active region comprised of a multiple quantum well active region and confinement layers having defined gratings and grating overgrowth regions to produce a laser device. The device also includes a current confinement layer including a sequence of doped n-p-n-p semiconductor layers to produce a n-p-n-p blocking structure and a semi-insulating semiconductor material deposited over the n-p-n-p blocking structure.

Hybrid confinement layers of buried heterostructure semiconductor laser

A method of accurately controlling the depth of etched gratings in uniform or layered quaternary III-V material. A native oxide is selectively grown on the area of the quaternary to be patterned and this native oxide is subsequently removed to engrave the surface. Periodic repetition of the oxide growth/removal steps results in gratings of the desired depths.

Method of etching patterns in III-V material with accurate depth control

Semiconductive photoanodes formed of titanium dioxide (TiO.sub.2) are known for use in photoelectrochemical cells. They have been made by various techniques, including chemical vapor deposition, thermal oxidation or anodic oxidation of thin titanium foils, hot pressing of TiO.sub.2 powder, and plasma spraying. The present invention provides a method for the fabrication of TiO.sub.2 thick film photoanodes, which method is simple, inexpensive and suitable for mass production of large area plates. The method comprises screen printing a film of conductive material on a clean alumina substrate which is then heated to fuse the conductive material into a conductive layer. A first layer of TiO.sub.2 particles in an organic carrier is then screen-printed over the conductive layer, at least 10% of the TiO.sub.2 being of anatase form. The structure is then heated to burn off the organic carrier and to transform at least part of the TiO.sub.2 from anatase form to rutile form, this resulting in good adhesion of the TiO.sub.2 layer to the conductive layer. A second layer of TiO.sub.2 is then screen-printed over the first layer and heated, the second layer being provided in case there should be pinholes in the first layer which would adversely affect the anode structure when submersed in an electrolyte. The resulting structure is then heated in a reducing atmosphere, e.g. anhydrous ammonia or hydrogen, to transform the TiO.sub.2 to TiO.sub.2-x where x is between 0 and 1, to reduce the electrical resistivity of the films.

Method of preparing TiO.sub.2 thick film photoanodes for

Growing community of inventors

Kanata, Canada

Cornelis Blaauw