Method of forming stable native oxide on gallium arsenide based compound semiconductors by combined drying and annealing

A method of forming a highly stable oxide on gallium arsenide containing compound semiconductors. A native oxide is grown on the surface of the semiconductor and dried during a suitable baking cycle. The oxide is then annealed at a temperature which is significantly higher than that of the baking cycle. This annealing step densifies the oxide and renders it particularly stable and impervious to impurities. In a particular embodiment, a diffusion mask is formed in accordance with the invention to permit selective area diffusion of impurities into a gallium arsenide containing compound semiconductor.