Hole transport in SiGe channels on step-bunched vicinal Si surfaces

✍ Scribed by R. Neumann; K. Brunner; G. Abstreiter

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 141 KB
• Volume: 13
• Category: Article
• ISSN: 1386-9477
• DOI: 10.1016/s1386-9477(02)00251-5

✦ Synopsis

Hole transport in narrow modulation doped Si1-xGex channels grown on vicinal Si(1 1 3) by molecular beam epitaxy is studied. Owing to the strong step-bunching properties of the Si(1 1 3) surface, the Si1-xGex channels exhibit regular terraces with a width of typical 250 nm and a mean step height of 4 nm, corresponding to 25 monolayers, when appropriate growth conditions are used. Considerable amount of Si1-xGex material accumulates at the step edges resulting in regular wire-like channel thickness variations. At low temperatures, we ÿnd a pronounced resistivity anisotropy for transport perpendicular and parallel to the step edges. The resistivity is maximum for the current ow perpendicular to the step edges. This can be explained by a lateral modulation of the hole conÿnement potential caused by the channel thickness variation near the step edges. Lowering the doping concentration, i.e. decreasing the e ective carrier density in the channel, enhances the resistivity anisotropy up to ⊥ = ≈ 16. We attribute this to an increasing resistivity of depleted SiGe layer regions in between the wire-like structures, when the Fermi energy gets comparable to the lateral potential barriers.