Scattering mechanisms in shallow undoped Si/SiGe quantum wells

• Main Authors: D. Laroche, S.-H. Huang, E. Nielsen, Y. Chuang, J.-Y. Li, C. W. Liu, T. M. Lu
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2015-10-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.4933026

We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.