Resonance Raman scattering of Si local vibrational modes in GaAs

We have studied the resonance of Raman scattering by Si local vibrational modes (LVM’s) in heavily doped GaAs prepared by ion implantation and rapid thermal annealing. For photon energies (1.9–2.7 eV) approaching the $E_1$ energy gap, similar resonance behavior was found for scattering by the Si on As site (${\mathrm{Si}}_{\mathrm{As}}$) LVM and by the longitudinal-optical phonon. Compared with undoped GaAs, both resonances are reduced in peak height and are broadened. This can be understood on the basis of a lowering and broadening of the ($E_1$,$E_1$+${\Delta }_1$) gap resonance due to residual implantation damage and due to the high dopant concentration. Scattering by the Si on Ga site (${\mathrm{Si}}_{\mathrm{Ga}}$) LVM, in contrast, shows no resonance enhancement for the above range of photon energies. However, excitation at 3.00 eV, which is almost in resonance with the $E_1$ gap energy, also enhances scattering by the ${\mathrm{Si}}_{\mathrm{Ga}}$ LVM, indicating a rather narrow $E_1$ gap resonance for that LVM. Taking advantage of that resonance we observe also Raman scattering by the ${\mathrm{Si}}_{\mathrm{Ga}}$ LVM in heavily doped GaAs layers grown by molecular-beam epitaxy down to a Si concentration of ∼${10}^{18}$ ${\mathrm{cm}}^{\mathrm{-}3}$.