Temperature Dependence of Charge Distributions and Carrier Mobility in an Undoped Si/SiGe Heterostructure

Capacitance-voltage ( {C} - {V} ) characteristics and carrier transport properties of 2-D electron gases (2DEGs) in an undoped Si/SiGe heterostructure at {T}= {4} - {35} K are presented. Two capacitance plateaus due to density saturation of the 2DEG in the buried Si quantum well (QW) are observed and explained by a model of surface tunneling. The peak mobility at 4 K is 4.1 \times 10^{{5}} cm2/ \text{V}\cdot \text{s} and enhanced by a factor of 1.97 at an even lower carrier density compared to the saturated carrier density, which is attributed to the effect of remote carrier screening. At {T}\,\,=35 K, the mobility enhancement with a factor of 1.35 is still observed, which suggests the surface tunneling is still dominant. ? 1963-2012 IEEE.