Piezospectroscopy and ab-initio calculations of carbon-oxygen complexes in gallium arsenide

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A carbon-oxygen complex (C, O) in gallium arsenide (GaAs) will be investigated by Fourier spectroscopy at low temperatures in the mid infrared. Background is the interest in light-element interactions in GaAs single crystals grown by Czochralski (LEC) or Bridgman (VGF) methods. Carbon and oxygen are introduced either inadvertently or deliberately to adjust to electrical properties. It is the aim to clarify the microscopic defect structure of the (C, O) center. During the previous project piezospectroscopic measurements have been performed successfully up to uniaxial pressure of 0.2 GPa in the [100], [110], and [111] crystallographic directions . The (C,O) center has tetragonal point symmetry. The intensity of the isotope shifted (18O, 12C) absorption band does not correspond to the natural abundance of the 18O isotope. In the present continuation of the project it is suggested to implant the isotopes 16O/18O as well as 12C/13C into pure GaAs substrates and to anneal the samples by rapid thermal annealing to generate the different isotope shift (C, O) absorption bands deliberately. The clarification of the number of oxygen atom involved in the complex is in the focus of the work. Ab-initio calculations are planned in parallel to test the stability and vibrational property of (C, O) centers fulfilling the required symmetry.