Spin filtering in magnetic II/VI semiconductor quantum dot systems

The research project is focused on the investigation of spin transport and spin filtering effects in semiconductor quantum dots placed in tunnel barriers. The dots under investigation will either be placed in a magnetically doped environment or coupled to a magnetic reservoir. The dots are fabricated by self-organized growth in molecular beam epitaxy (MBE). We will investigate II/VI semiconductors, especially CdSe quantum dots in an n-doped dilute magnetic environment. For these dots a local coupling between the electrons in a single dot and the surrounding Mn ions has already been demonstrated. The effect leads to a local ferromagnetic coupling with a zero field giant Zeeman splitting although the system is intrinsically not ferromagnetic. This makes such systems suitable spin filters even without any external magnetic field. These dots will be investigated in large area and sub micron sized mesas, the latter may also be fitted with side gates for control of the electronic levels. In addition we will investigate systems fitted with dilute magnetic emitters or stacked quantum dot systems for the demonstration of spin filtering and detection of spin polarized currents by quantum dots.