Effects of radio frequency power on the optical and electrical properties of germanium carbon films

Abstract

The relative integrated intensity of the three components in C 1s with different RF power. • Amorphous germanium carbon films are fabricated by reactive sputtering in a CH 4 + H 2 + Ar mixture. • Optical, electrical and chemical bonding properties are investigated. • The effects of composition and chemical bonding on optical properties are investigated. • We found that high RF power and Ge content can promote the forming of Ge–C bond. We have prepared amorphous hydrogenated germanium carbon (a-Ge 1− x C x :H) films by radio frequency (RF) reactive magnetron sputtering and their composition, optical, electrical and chemical bonding properties are investigated as a function of RF power. The results show that the deposition rate increases and the optical gap of the a-Ge 1− x C x :H films decreases as RF power increases from 30 to 90 W. The decrease of the optical gap is mainly due to the decrease in the carbon content. As increasing RF power, the refractive index of the films increases and the absorption edge shifts to long wavelength region. Besides, the room temperature dark conductivity increase with RF power is due to the decrease of the activation energy connected with the increase of Ge content. Through the analysis of X-ray photoelectron spectroscopy (XPS), we found that the formation of Ge–C bonds in the films is promoted by high RF power connected with relatively high self-bias and Ge content.