Ge-rich islands grown on patterned Si substrates by low-energy plasma-enhanced chemicalvapour deposition

Abstract

Si1 − xGex islands grown on Si patterned substrates have received considerable attention during thelast decade for potential applications in microelectronics and optoelectronics. In thiswork we propose a new methodology to grow Ge-rich islands using a chemicalvapour deposition technique. Electron-beam lithography is used to pre-pattern Sisubstrates, creating material traps. Epitaxial deposition of thin Ge films by low-energyplasma-enhanced chemical vapour deposition then leads to the formation of Ge-richSi1 − xGex islands(x > 0.8) with a homogeneous size distribution, precisely positioned with respect tothe substrate pattern. The island morphology was characterized by atomicforce microscopy, and the Ge content and strain in the islands was studied byμRaman spectroscopy. This characterization indicates a uniform distribution of islands with high Gecontent and low strain: this suggests that the relatively high growth rate (0.1 nm s − 1) and lowtemperature (650 °C) used is able to limit Si intermixing, while maintaining a long enough adatom diffusionlength to prevent nucleation of islands outside pits. This offers the novel possibility of usingthese Ge-rich islands to induce strain in a Si cap.