Source Contamination Effects on the Epitaxy of Ge Films on Ge

The effect of source contamination on the structure of Ge films deposited simultaneously onto single-crystal Ge substrates and amorphous quartz Hall substrates has been investigated. Deposition from the refractory metals, from quartz crucibles, and from extensively outgassed and vacuum-loaded graphite crucibles, produce single-crystal films when deposited at a substrate temperature of 350 °C; the electrical properties of the films deposited simultaneously onto the Hall substrates are typical of Ge films with good structural properties. Deposition from un-outgassed graphite crucibles (either resistive or radiative heating) and $Al2O3$ in either crucible or cataphoretic forms, produce films ranging from amorphous to polycrystalline when deposited on single-crystal Ge at 350 °C. Evaporations from these latter materials will produce single-crystal films on Ge single crystals only for extensive vacuum outgassing and vacuum loading of the Ge charge and for substrate temperatures in excess of 500 °C.