Abstract
Second-harmonic generation (SHG) from electric-field biased superlattices and step asymmetry wells were studied. Contributions from the different sources to second-order susceptibility were systematically analyzed for these two kinds of asymmetry Si/Ge quantum-well structures. The bulklike was large enough to be observed while the strain-induced contribution to was relatively small for superlattices under an applied field of 100 kV/cm. However, strain-enhanced effects were large compared to the contribution from the bulk for the optical in SiGe/Si step wells. The results show that different asymmetric structures have different contributional distributions of SHG sources. The peak value of was as large as for a superlattice under 100 kV/cm electric field and for SiGe/Si step wells. These large bulklike values indicate that Si/Ge quantum wells with asymmetric structures have potential applications to optoelectronic materials and devices with the existing Si-based technology.
- Received 14 May 1997
DOI:https://doi.org/10.1103/PhysRevB.56.15842
©1997 American Physical Society