Determination of Optical Band Gap and Germanium Content of Hydrogenated Micro-Crystalline Si1-xGex Films by Ultraviolet-Visible and Auger Electron Spectroscopy Measurements

Abstract

We report a reasonable method for determination of optical band gap (E-g) and germanium content (x) of hydrogenated micro-crystalline silicon-germanium (mu c-Si1-xGex:H) thin-film by using ultraviolet-visible (UV-visible) and Auger electron spectroscopy (AES) measurements. For reasonable extraction of the E-g of mu c-Si1-xGex:H film, we used a plot of (alpha h nu)(1/4) versus photon energy (E-ph) for a wide range of E-ph. The simplest explanation of the 1/4 power could be a superposition of absorptions from micro-crystalline structure. We also measured the x as a function of E-g of the mu c-Si1-xGex:H thin-film. Using UV-visible, E-g was measured to be varying from 1.043 to 1.079 eV and x was extracted to be between 0.107 to 0.188. From AES measurements, the E-g was extracted between 1.045 to 1.075 eV while x was measured between 0.110 to 0.182. The results of the comparative analysis of UV-visible and AES measurement were performed.