Correlation between the electrooptical properties and the composition of α-Si1−xGex:H (x<0.1) thin films

Abstract

Abstract Amorphous silicon-germanium alloys α- Si 1–x Ge x : H (x have been prepared by RF magnetron reactive co-sputtering of Si and Ge in Ar+H2 gas mixture with 5% hydrogen concentration. The total pressure, the substrate temperature and RF frequency were kept constant at 0.5 Pa, 200°C and 13.56 MHz, respectively. The RF power was varied from 100 to 200 W. The H concentration in the films have been investigated by elastic recoil detection (ERD) analysis. The Si and Ge composition and the density of the films have been determined by the Rutherford back scattering method. The properties have been measured as a function of the RF power. The results are reported of the optical gap, refractive index, density, and dark conductivity at room temperature, thermal activation energy of the dark conductivity, IR absorption and Raman spectra as function of the RF power as well as the film composition. It has been found that the properties are influenced by the H2 content in the films rather than by the Ge content. The small quantity of Ge reduces the density of localized gap states.