Abstract: A group III-V substrate is doped with tellurium or another group VI element, instead of silicon, in order to avoid the conductivity type conversion that could otherwise occur if the group V element is boiled off during high temperature processing. For example, a gallium arsenide substrate can be doped with tellurium and then a gallium arsenide epitaxial layer can be deposited on a surface. If the substrate is heated beyond a predetermined temperature during the processing of the device, the arsenic can boil away from the substrate and leave arsenic vacancies. If the silicon is used as the substrate dopant, the silicon can migrate to the arsenic vacancies and replace arsenic, particularly proximate the substrate surface. If, on the other hand, tellurium or another group VI element is used as the substrate dopant, this change in conductivity type can not occur. Therefore, the conductivity conversion proximate the substrate surface will not create a thyristor-like behavior that is significantly disadvantageous.

Abstract: Disclosed is an optical coupler apparatus comprising a photo-emissive device and a photo-sensitive device responsive to the wavelengths emitted by the source. The devices are mounted on frame leads with their major faces opposed and spaced apart. The optical devices and a substantial portion of the supporting frame leads are then encapsulated in a molded body of substantially electrically non-conductive material which is substantially transparent to the operative wavelengths of the optical devices.The transparent material not only fills the space between the optical devices but also provides structural support for the leads. The transparent material is then covered with an opaque coating or an additional body of opaque material molded over the body of transparent material.