Band offset predictions for strained group IV alloys: Si1-x-yGexCy on Si(001) and Si1-xGex on Si1-zGez(001)

The band offsets for strained Si1-x-yGexCy layers grown on Si(001) substrat e and for strained Si1-xGex layers grown on fully relaxed Si1-zGez virtual substrates are estimated. The hydrostatic strain, the uniaxial strain and t he intrinsic chemical effect of Ge and C are considered separately. Unknown material parameters relative to the latter effect are chosen to give the b est agreement with the available experimental results for Si1-xGex and Si1- yCy layers on Si. As a general trend concerning carrier confinement opportu nities, it is found that a compressive strain is required to obtain a sizea ble valence band offset, while a tensile strain is needed to obtain a condu ction band discontinuity. In most cases the strain is responsible for a ban dgap narrowing with respect to that of the substrate. The obtained results are in very good agreement with available experimental determinations of ba nd offsets and bandgap changes for ternary alloys on Si(001).