Electrodeposited germanium on silicon substrate using a mixture of germanium tetrachloride and propylene glycol

Abstract

We report the deposition of germanium (Ge) film on silicon (Si) substrate by a simple and low cost electrochemical deposition using a mixture of germanium tetrachloride (GeCl4) and propylene glycol (C3H8O2). The effects of deposition environment and applied current density on the properties of deposited Ge films were investigated. Ge film containing germanium dioxide (GeO2) microclusters was obtained for deposition in air-exposed environment while high purity Ge film with no impurity detectable by energy-dispersive x-ray spectroscopy (EDS) was obtained in nitrogen (N2) filled environment. In Raman spectra, N2 exposed sample shows smaller full width at half maximum (FWHM) values of Ge-Ge peak compared to air exposed sample, thereby indicating better crystallinity of Ge. Relatively flat and smooth Ge surfaces with the average roughnesses of 0.828-1.069 nm were obtained for all tested current densities of 10, 20 and 60 mAcm-2. The mean Ge crystallite grain sizes were determined to be in the range of 2-4 nm. In qualitative voltammetry study, two reduction peaks were observed in cyclic voltammograms measurement which confirms that the deposition of Ge at cathode occurs via two reduction processes. It is expected that the impurity-free Ge film on Si is promising for various device application towards heterogeneous integration on Si platform.