Growth and properties of microcrystalline germanium–carbide alloys grown using electron cyclotron resonance plasma processing

We report on the growth and properties of a new material, microcrystalline (Ge, C), which has potentially important optical, electrical and structural properties. The material was grown using a remote, low pressure electron cyclotron resosnance (ECR) plasma process on glass, stainless steel and c-Si substrates. The growth was done with hydrogen dilution and ion bombardment at temperatures of 350–400°C. We discovered that the optical absorption curve parallels that of c-Ge, with increased bandgaps as C is incorporated. We obtained up to 2% C incorporation, which increased the gap to 1.1 eV. At comparable bandgaps, the absorption coefficient of the (Ge, C) material is much larger than that of c-Si. Raman and X-ray measurements detected microcrystalline structure, and a dependence of grain size on the substrate used. The lattice constant contracted with C incorporation, approximately obeying Vegard’s law. Both undoped and n-doped materials were grown.