Thin Films of Amorphous Silicon-Germanium Alloys Prepared by Radio-Frequency Magnetron Sputtering

Abstract

Thin films of amorphous silicon‐germanium alloy were prepared by sputtering silicon and germanium targets with argon in a radio‐frequency (rf) magnetron sputtering system. For the film prepared at an rf power of 200 W, the energy gap and the refractive index showed monotonous changes between those for silicon and germanium with a deviation from linearity in the correlating line of the energy gap. The deviation was attributable to the decrease in structural disorder in the film as shown in Tauc coefficient B. For the film prepared at an rf power of 50 W, some deviations of the energy gap and the refractive index from the monotonous changes increased with decreasing x, because of an excess amount of dangling silicon bonds. Fourier transform infrared spectra indicated absorption due to the modes derived from the dangling bonds. The absorption coefficient showed that the deviations of the energy gap and the refractive index at x = 0 were proportional to the excess amount of dangling bonds of silicon. The excess amount of dangling bonds of silicon retarded crystallization in the solid state. © 2000 The Electrochemical Society. All rights reserved.