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

The temperature dependence of the mobility of the two-dimensional electron gas (2DEG) in a silicon quantum well strained by Si _0.7 Ge _0.3 relaxed buffer layer is determined precisely by a mobility spectrum analysis. The 2DEG mobility is 2780 cm ²/V s at room temperature and, upon cooling, increases continuously to reach 2 DEG = 7. 4 × 10 ⁴ cm ² / V s at 7 K. A back gate installed on the sample changes the 2DEG _concentration n successfully to establish μ2 DEG n ^1.4 at the constant temperature T = 10 K, 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 _2DEG 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 (u = 9. 5 eV), LO phonon deformation potential for g-process scattering (D 0 = 9. 0 × 10 ⁸ eV / cm), and sheet density of remote ionized impurities that have been determined by quantitative comparison with our experimental results. The temperature dependence of μ2 DEG _calculated theoretically show excellent agreement with experimentally determined 2 DEG.