Hole mobilities in pseudomorphic Si1-x-yGexCy alloy layers

Abstract Transport properties of boron doped tensile strained, perfectly strain compensated and compressively strained Si 1− x − y Ge x C y alloy layers on Si(001) substrates are presented. The room temperature mobility decreases with C and Ge alloy concentration compared to pure Si from 180 cm 2 /Vs ( p =3×10 17 cm −3 ) to 120 cm 2 /Vs, which is explained by the increasing alloy scattering and enhanced scattering at optical phonons. At temperatures below 100 K a higher mobility is measured for the samples containing C due to the lower carrier concentration, and because ionized impurity scattering becomes dominant. The temperature dependence of the hole density is used to determine the boron activation energy E A . We observe an activation energy of about 32 meV in Si 0.94 Ge 0.06 . With carbon incorporation E A first decreases to 27 meV and then increases to 36 meV for the strain compensated sample. In modulation doped p-type Si 1− x − y Ge x C y quantum wells, we observe an increased hole mobility with C alloying compared to reference samples without C. This is a consequence of reduced strain and C induced decreased hole concentration in the quantum well.