The effective electron mass in high-mobility SiGe/Si/SiGe quantum wells

TL;DR

This study measures the effective electron mass in high-mobility SiGe/Si/SiGe quantum wells, revealing its dependence on electron density and independence from disorder in high-quality samples.

Contribution

It provides a detailed analysis of how the effective mass varies with electron density and demonstrates its disorder independence in high-mobility quantum wells.

Findings

Effective mass increases as electron density decreases.

The relation m*/m_b=n_s/(n_s-n_c) describes the mass dependence.

Effective mass is disorder-independent in high-mobility samples.

Abstract

The effective mass, m*, of the electrons confined in high-mobility SiGe/Si/SiGe quantum wells has been measured by the analysis of the temperature dependence of the Shubnikov-de Haas oscillations. In the accessible range of electron densities, n_s, the effective mass has been found to grow with decreasing n_s, obeying the relation m*/m_b=n_s/(n_s-n_c), where m_b is the electron band mass and n_c~0.54*10^11 cm^-2. In samples with maximum mobilities ranging between 90 and 220 m^2/Vs, the dependence of the effective mass on the electron density has been found to be identical suggesting that the effective mass is disorder-independent, at least in the most perfect samples.