Synthesis of strained SiGe on Si(100) by pulsed laser induced epitaxy

Pulsed laser induced epitaxy (PLIE), based on melting/solidification processes induced by nanosecond laser pulses, is used to synthesize pseudomorphic Si_1 − xGe_x epilayers from 20 to 80 nm thick Ge layers evaporated on a Si(100) wafer. Ge concentration and strain are characterized by transient reflectivity, energy dispersive X-ray analysis and X-ray diffraction from symmetric (004) and asymmetric (224) reflections. For a low Ge thickness or a high laser fluence, PLIE builds up only a pseudomorphic strained Si_1 − xGe_x layer with a graded Ge composition reaching x ≈ 19% near the surface. When the Ge amount is in excess to achieve this situation, PLIE forms additionally a relaxed Si_1 − xGe_x layer with x values up to ≈40% over the previous pseudomorphic layer.