Fully coherent Ge islands growth on Si nano-pillars by selective epitaxy

Abstract

Our recent experimental results of Ge nanoheteroepitaxy (NHE) on Si nanopillars (NPs) are reviewed to confirm the possibility of relaxed Ge growth on Si without misfit dislocations (MDs) formation by elastic deformation. Selective Ge growth is performed by using reduced pressure chemical vapor deposition (CVD) on two types of Si NPs with thermal SiO₂ or CVD SiO₂ sidewalls and on Si nanoislands (NIs) on SiO₂. By using thermal SiO₂ sidewall, compressive strain is generated in the Si pillar and fixed by the thermal SiO₂. This results in an incoherent Ge growth on Si NPs due to MD formation. By using CVD SiO₂ sidewall, tensile strain formation due to thermal expansion during prebake for Ge epi process is observed. However, strain in Si due to Ge growth is not dominant. By introducing a Si_0.5Ge_0.5 buffer layer, no MD and stacking faults are observed by cross section TEM. The shape of Ge on Si NPs becomes more uniform due to improved crystal quality. On Si NIs on SiO₂, a clear compliance effect is observed after Ge growth. Coherent growth of Ge on Si is also realized on Si NIs by using Si_0.5Ge_0.5 buffer.

Keywords

Selective Ge epitaxy,

Heteroepitaxial growth,

Coherent growth,

Strain,

Relaxation

Source:Sciencedirect

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