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.