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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 E₁ energy gap, similar resonance behavior was found for scattering by the Si on As site (Si₀ₒ) 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 (E₁, E₁+₁) gap resonance due to residual implantation damage and due to the high dopant concentration. Scattering by the Si on Ga site (Si₆₀) 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 E₁ gap energy, also enhances scattering by the Si₆₀ LVM, indicating a rather narrow E₁ gap resonance for that LVM. Taking advantage of that resonance we observe also Raman scattering by the Si₆₀ LVM in heavily doped GaAs layers grown by molecular-beam epitaxy down to a Si concentration of 10^18 cm^-3.
Ramsteiner et al. (Tue,) studied this question.