Experimental and theoretical analysis of the temperature dependence of the two-dimensional electron mobility in a strained Si quantum well

Abstract

The temperature dependence of the mobility of the two-dimensional electron gas (2DEG) in a silicon quantum well strained by Si0.7Ge0.3 relaxed buffer layer is determined precisely by a mobility spectrum analysis. The 2DEG mobility is 2780 cm2/V s at room temperature and, upon cooling, increases continuously to reach μ2DEG=7.4×104cm2/Vs at 7 K. A back gate installed on the sample changes the 2DEG concentration n successfully to establish μ2DEG∝n1.4 at the constant temperature T=10K, implying that the scattering at such low temperature is limited solely by the remote ionized impurity scattering. Based on this finding, theoretical analysis of the temperature dependence of μ2DEG is performed based on the relaxation time approximation using 2DEG wavefunctions and subband structures determined self-consistently and including three major scatterings; by intravalley acoustic phonons, intervalley g-processes of longitudinal optical (LO) phonons, and remote ionized impurities. The calculation included only three fitting parameters, the shear deformation potential (Ξu=9.5eV), LO phonon deformation potential for g-process scattering (D0=9.0×108eV/cm), and sheet density of remote ionized impurities that have been determined by quantitative comparison with our experimental results. The temperature dependence of μ2DEG calculated theoretically show excellent agreement with experimentally determined μ2DEG.