Spectroscopic review of hydrogenated, carbonated and oxygenated group IV alloys

Abstract

Semiconductors based on group IV elements are widely used in the fields of micro-electronics, optics and photonics. The group IV alloys are processed using plasma enhanced chemical vapor deposition and its opto-electrical properties are a result of the material composition and structure. Infrared and Raman spectroscopy are complementary and powerful tools for providing these essential material characteristics. In this work, the vibrational modes present in hydrogenated, oxygenated and carbonated group IV alloys are investigated in a unique range of amorphous and nano-crystalline Si_X≥0Ge_1−X:H films and their alloys with C, O and Sn. Measurements are performed both post-deposition and following extended exposure to the ambient and de-ionized water. This comprehensive review is of value in the fields of material science and engineering as a single work of reference for group IV peak identification. Additionally, the effect of electrical screening, the influence of the dielectric medium on the peak frequency of a vibrational mode, is illustrated using the experimentally observed frequency shifts of X-O and X-H (X = C, Si, Ge) vibrational modes. All experimentally observed center frequencies of silicon hydride stretching modes in silicon solids and corresponding silicon-hydride configurations are identified using a straightforward Lorentz-Lorenz model approximation and considering all potential hydrogenated volume deficiencies within a tetrahedrally coordinated amorphous and nanocrystalline lattice. It shows that the stretching mode signature can reveal detailed information on the volume deficiencies in IV-valence alloys.