Si1-xGex single crystals grown by the Czochralski method: Defects and electrical properties

Abstract

Defects in Si1-xGex single crystals (2-8.5 at.% Ge) grown by the Czochralski method are investigated by synchrotron white beam topography and phase contrast imaging techniques. As the Ge concentration increases, dislocation structure evolves from individual dislocations to slip bands and sub-grain boundaries. We discuss the effect of dislocations on the electrical characteristics such as resistivity rho(nu), the Hall hole mobility mu(p) and carrier lifetime tau(e). Diodes are fabricated by bonding p-Si1-xGex to n-Si wafers to investigate I-V characteristics and reverse recovery process. I-V characteristics are not deteriorated in spite of a five times decrease in tau(e) with Ge concentration. A small reverse recovery time (determined by the accumulated charge) can be achieved for an optimised preset Ge concentration.