Mobility of the non-polarized and the spin-polarized electron gas in Si/SiGe heterostructures: Remote impurities

¹ Centre d'Elaboration de Materiaux et d'Etudes Structurales (CNRS) - 29 Rue Jeanne Marvig, 31055 Toulouse, France, EU
² UFR-PCA, Université Paul Sabatier - 118 Route de Narbonne, 31062 Toulouse, France, EU

^a gold@cemes.fr

Received: 21 October 2010
Accepted: 27 November 2010

Abstract

We analyze low-temperature ultra-high–mobility data (μ ≤ 1.6×10⁶  cm² /Vs) obtained for the two-dimensional electron gas in Si/SiGe heterostructures with Al₂O₃ as the gate oxide. We find that charged impurities of density N_id = 5.5×10¹²  cm⁻², located at the SiGe/Al₂O₃ interface at a distance d = 1500 Å from the electron gas, are important for the mobility. A metal-insulator transition is predicted at low electron density (near 2×10¹⁰  cm⁻²). We discuss the importance of many-body effects (exchange and correlation) for the mobility for the non-polarized and the spin-polarized electron gases. Suggestions are made to increase the mobility in such structures.