Highly doped GaAs:Si by molecular beam epitaxy

Highly doped (N++) GaAs:Si with n up to 1.8×1019 cm−3 has been grown by molecular beam epitaxy at a ‘‘normal’’ growth rate of ∼0.8 m/h−1. These layers have been studied by Raman spectroscopy, van der Pauw–Hall measurements, and capacitance-voltage plotting. They show no appreciable surface accumulation or diffusion of donors into low-doped layers grown on top of them, and thus should be suitable as buffer layers for n/N+ devices as well as aiding in the production of low resistivity ohmic contacts. Resistivity of these layers has a lower limit of 4.75×10−4 Ω cm occurring at about 1.2×1019 cm−3. The possibility of this being an intrinsic lower limit to the resistivity of GaAs is discussed.