Epitaxial growth of CdMnTe quantum dots directly on Si(111)

摘要

The presence of magnetic ions in a diluted magnetic semiconductor (DMS) leads to a variety of electronic, optical and magneto-optical properties. For instance, the exchange interaction between the magnetic ions spin and the spin of carriers leads to formation of bound magnetic polarons (BMPs). In a diluted magnetic quantum dot (DMQD), the possibility of tuning the three dimensional confinement originates new magnetic effects not present in bulk or quantum wells and makes MPs a very interesting system. Recently, formation of robust MPs has been observed in type-Ⅱ DMQDs, due to the spatial separation of electrons and holes. In this work, we report the growth and structural characterization of CdMnTe/Si quantum dots. The samples were grown by molecular beam epitaxy directly on Si(Ⅲ) substrates, in contrast with the previously studied systems, where the DMS islands were grown on Ⅱ-Ⅵ buffers layers. The use of Silicon as substrates is advantageous for its compatibility with most processes of the microelectronic industry. We have used atomic force microscopy, high-resolution transmission electron microscopy and high-resolution x-ray diffraction to investigate the effect of growth time and temperature on the morphology and structural characteristics of the quantum dots. Our results show that this system follows the Volmer-Weber growth mode and almost perfect epitaxial islands can be grown despite a lattice mismatch around 19%. The introduction of a small concentration Mn ions improves the structural quality of the islands, as observed by high resolution x-diffraction around the (Ⅲ) Bragg reflection.