Effect of Post-Growth Annealing on Morphology of Ge Mesa Selectively Grown on Si

Sungbong PARK; Yasuhiko ISHIKAWA; Tai TSUCHIZAWA; Toshifumi WATANABE; Koji YAMADA; Sei-ichi ITABASHI; Kazumi WADA

doi:10.1093/ietele/e91-c.2.181

Special Section on Silicon Photonics Technologies and Their Applications

Effect of Post-Growth Annealing on Morphology of Ge Mesa Selectively Grown on Si

Sungbong PARK, Yasuhiko ISHIKAWA, Tai TSUCHIZAWA, Toshifumi WATANABE, Koji YAMADA, Sei-ichi ITABASHI, Kazumi WADA

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Keywords: Ge-on-Si photodetector, selective epitaxial growth, UHV-CVD, post-growth annealing, morphological instability

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2008 Volume E91.C Issue 2 Pages 181-186

DOI https://doi.org/10.1093/ietele/e91-c.2.181

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Abstract

Effect of the post-growth annealing on the morphology of a Ge mesa selectively grown on Si was studied from the viewpoint of near-infrared photodiode applications. By ultrahigh-vacuum chemical vapor deposition, Ge mesas were selectively grown at 600°C on Si (001) substrates partially covered with SiO₂ masks. The as-grown Ge mesas showed trapezoidal cross-sections having a top (001) surface and {311} sidewall facets, as similar to previous reports. However, after the subsequent post-growth annealing at -800°C in the ultrahigh-vacuum chamber, the mesas were deformed into rounded shapes having a depression at the center and mounds near the edges. Such a deformation cannot be observed for the samples annealed once after cooled and exposed to the air. The residual hydrogen atoms on the Ge surface from the germane (GeH₄) decomposition is regarded as a trigger to the observed morphological instability, while the final mesa shape is determined in order to minimize a sum of the surface and/or strain energies.

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