Raman spectroscopic assessment of carbon-hydrogen pairs in carbon-doped GaAs layers

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Abstract
Raman scattering by local vibrational modes of carbon‐hydrogen pairs is reported for heavily carbon‐doped epitaxial GaAs layers. Scattering by the longitudinal carbon mode of these pairs at 452 cm−1 shows a strong resonant enhancement for incident photon energies approaching the E1 band‐gap energy of GaAs (≂3 eV). A possible mechanism for this resonance behavior is discussed in terms of the displacement of the carbon atom from its normal arsenic lattice site accompanied by a lengthening and weakening of the carbon‐gallium bonds when carbon‐hydrogen pairs form. The present findings demonstrate that resonant Raman scattering is an attractive tool for the detection of carbon‐hydrogen pair formation in thin carbon‐doped epitaxial GaAs layers grown from source materials containing hydrogen. The detection limit is estimated to be in the low 1018 cm−3 range.