High-mobility capacitively-induced two-dimensional electrons in a lateral superlattice potential

作者：Lu T M^*; Laroche D; Huang S H; Chuang Y; Li J Y; Liu C W

来源：Scientific Reports, 2016, 6(1): 20967.

DOI：10.1038/srep20967

In the presence of a lateral periodic potential modulation, two-dimensional electrons may exhibit interesting phenomena, such as a graphene-like energy-momentum dispersion, Bloch oscillations, or the Hofstadter butterfly band structure. To create a sufficiently strong potential modulation using conventional semiconductor heterostructures, aggressive device processing is often required, unfortunately resulting in strong disorder that masks the sought-after effects. Here, we report a novel fabrication process flow for imposing a strong lateral potential modulation onto a capacitively induced two-dimensional electron system, while preserving the host material quality. Using this process flow, the electron density in a patterned Si/SiGe heterostructure can be tuned over a wide range, from 4.4 x 10(10) cm(-2) to 1.8 x 10(11) cm(-2), with a peak mobility of 6.4 x 10(5) cm(2)/V.s. The wide density tunability and high electron mobility allow us to observe sequential emergence of commensurability oscillations as the density, the mobility, and in turn the mean free path, increase. Magnetic-field-periodic quantum oscillations associated with various closed orbits also emerge sequentially with increasing density. We show that, from the density dependence of the quantum oscillations, one can directly extract the steepness of the imposed superlattice potential. This result is then compared to a conventional lateral superlattice model potential.

• 出版日期2016-2-11
• 单位中国科学院电工研究所