Photodetection in Hybrid Single-Layer Graphene/Fully Coherent Germanium Island Nanostructures Selectively Grown on Silicon Nanotip Patterns

详细信息    查看全文

• 作者：Gang Niu ; Giovanni Capellini ; Grzegorz Lupina ; Tore Niermann ; Marco Salvalaglio ; Anna Marzegalli ; Markus Andreas Schubert ; Peter Zaumseil ; Hans-Michael Krause ; Oliver Skibitzki ; Michael Lehmann ; Francesco Montalenti ; Ya-Hong Xie ; Thomas Schroeder
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：January 27, 2016
• 年：2016
• 卷：8
• 期：3
• 页码：2017-2026
• 全文大小：535K
• ISSN：1944-8252

文摘

Dislocation networks are one of the most principle sources deteriorating the performances of devices based on lattice-mismatched heteroepitaxial systems. We demonstrate here a technique enabling fully coherent germanium (Ge) islands selectively grown on nanotip-patterned Si(001) substrates. The silicon (Si)-tip-patterned substrate, fabricated by complementary metal oxide semiconductor compatible nanotechnology, features ～50-nm-wide Si areas emerging from a SiO₂ matrix and arranged in an ordered lattice. Molecular beam epitaxy growths result in Ge nanoislands with high selectivity and having homogeneous shape and size. The ～850 °C growth temperature required for ensuring selective growth has been shown to lead to the formation of Ge islands of high crystalline quality without extensive Si intermixing (with 91 atom % Ge). Nanotip-patterned wafers result in geometric, kinetic-diffusion-barrier intermixing hindrance, confining the major intermixing to the pedestal region of Ge islands, where kinetic diffusion barriers are, however, high. Theoretical calculations suggest that the thin Si/Ge layer at the interface plays, nevertheless, a significant role in realizing our fully coherent Ge nanoislands free from extended defects especially dislocations. Single-layer graphene/Ge/Si-tip Schottky junctions were fabricated, and thanks to the absence of extended defects in Ge islands, they demonstrate high-performance photodetection characteristics with responsivity of ～45 mA W^–1 and an I_on/I_off ratio of ～10³.