Effect of oxygen on minority-carrier lifetime and recombination currents in Si1− x Ge x heterostructure devices

A p+-i-n diode structure is presented which is suitable for determining the recombination lifetime in thin Si1−xGex layers grown on Si. Electrical measurements and computer simulations are used to extract carrier lifetimes in Si1−xGex layers with various oxygen concentrations. The minority-carrier lifetime increases dramatically as the oxygen concentration in the Si1−xGex decreases from 3×1020 to less than 3×1017 cm−3. Lifetimes extracted from the p+-i-n diodes are consistent with those obtained from measurements on heterojunction bipolar transistors with high oxygen concentrations in the Si1−xGex base.