Raman study of Si+‐implanted GaAs

The effect of Si+ implantation on the allowed and forbidden first‐order and on the resonantly excited second‐order Raman spectrum of GaAs has been studied. The implantation dose was varied between 5×1011 and 1×1016 ions/cm2. For doses exceeding 1015 cm−2, the Raman spectrum of a completely amorphized surface layer was observed. In samples implanted with doses ≤1015 cm−2, which show a partly crystalline/amorphous mixed state, the relative intensities of amorphous and crystalline features in the Raman spectrum vary significantly for different exciting photon energies. This is explained by differences in the dispersion of the Raman susceptibility in amorphous and crystalline GaAs. Dipole‐forbidden but defect‐induced first‐order scattering by longitudinal optical zone center [LO(Γ)] phonons shows an initial increase with implantation dose, which is, for excitation resonant with the E1 gap, followed by a saturation and even a decrease in intensity. This is understood in terms of an implantation‐induced broaden...