Dopant incorporation and activation in highly Si doped GaAs layers grown by atomic layer molecular beam epitaxy

Highly Si doped GaAs layers grown by atomic layer molecular beam epitaxy (ALMBE) were studied by Raman spectroscopy of local vibrational modes and coupled plasmon-phonon modes as well as by Hall effect measurements. For layers grown at substrate temperatures of 200, 300 and 400 degree C, respectively, high free carrier concentrations of up to 2.2 x 10 high 19 cm high -3 at 10 K are achieved as deduced from Raman scattering by coupled plasmon-phonon modes. For this concentration the Fermi level lies 350 meV above the Gamma conduction band edge which exceeds the Gamma-L conduction band separation reported for lightly doped GaAs. This indicates an increase of the Gamma-L separation in the present highly doped material due to band renormalization effects.