Gallium arsenide semiconductor devices fabricated with insulator layer

A method of forming an insulator on a single crystal gallium arsenide substrate, comprising the steps of:

• (a) providing a single crystal gallium arsenide substrate having a clean substrate surface in a chamber;
• (b) heating the single crystal gallium arsenide substrate in a vacuum formed within the chamber;
• (c) introducing arsenic gas within the chamber;
• (d) introducing a Group IIa metal fluoride vapor into the chamber at a rate effective to form a homogenous layer comprised of a monolayer of Group IIa atoms attached directly onto said gallium arsenide substrate surface as the reaction product of a reaction between the Group IIa metal fluoride vapor and the clean substrate surface in the presence of the arsenic gas at said substrate surface and such that the homogenous layer is substantially free of Group IIa atoms unreacted with the gallium arsenide substrate surface when the monolayer is completed;
• (e) continuing introducing Group IIa metal fluoride vapor into the chamber, after forming said monolayer in step (d), at a rate effective to deposit a single crystal epitaxial film of Group IIa fluoride onto the monolayer;
• and
• (f) discontinuing arsenic gas introduction during step (e).