Low-temperature growth of Ge on Si(100)

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Abstract
Heteroepitaxial MBE growth of Ge on Si(100) is studied at temperatures down to room temperature. We show that, as for Si and GaAs homoepitaxy, the low-temperature limit to growth is an epitaxial thickness, hepi, before the amorphous phase is nucleated. hepi increases with increasing temperature with an apparent activation energy of 0.5±0.1 eV at 0.2 Å/s. Above 170 °C hepi increases discontinuously and becomes effectively infinite, possibly as solid phase begins to occur. We show that growth is planar for all temperatures below 300 °C, so that low-temperature growth can be used near 200 °C to suppress island formation without encountering the limited thickness effect. In contrast with planar growth at high temperatures with an As ‘‘surfactant’’, strain relaxation of these planar epilayers occurs by normal dislocation introduction to give an array of predominantly edge misfit dislocations.