Hole mobilities in pseudomorphic Si1-x-yGexCy alloy layers

Transport properties of boron doped tensile strained, perfectly strain comp ensated and compressively strained Si1-x-yGexCy alloy layers on Si(001) sub strates are presented. The room temperature mobility decreases with C and G e alloy concentration compared to pure Si from 180 cm(2)/Vs (p = 3 x 10(17) cm(-3)) to 120 cm(2)/Vs, which is explained by the increasing alloy scatte ring and enhanced scattering at optical phonons. At temperatures below 100 K a higher mobility is measured for the samples containing C due to the low er carrier concentration, and because ionized impurity scattering becomes d ominant. The temperature dependence of the hole density is used to determin e the boron activation energy E-A. We observe an activation energy of about 3 meV in Si0.94Ge0.06. With carbon incorporation E-A first decreases to 27 meV and then increases to 36 meV for the strain compensated sample. In mod ulation doped p-type Si1-x-yGexCy quantum wells, we observe an increased ho le mobility with C alloying compared to reference samples without C. This i s a consequence of reduced strain and C induced decreased hole concentratio n in the quantum well. (C) 1998 Elsevier Science S.A. All rights reserved.