ANGLE-RESOLVED MAGNETO-TUNNELING SPECTROSCOPY TO PROBE VALENCE-BAND ANISOTROPY IN SI/SI1-XGEX QUANTUM-WELLS

The resonances of a resonant tunneling structure are probed by a magnetic field applied parallel to the interfaces, which enables us to investigate the local band structure in k space. By rotating the magnetic field in the plane of the interfaces the energy surface at constant k(parallel-to) is investigated. Using this technique differently strained Si/Si1-xGex quantum wells were studied, where with a large anisotropy of the energy levels was seen, with the symmetry axes of light holes and heavy holes being rotated 45-degrees with respect to each other. In the case of resonant tunneling diodes with relaxed Si1-xGex quantum wells grown on thick, relaxed Si1-xGex buffer layers, the anisotropy is smaller, and without complete symmetry between different 90-degrees in-plane directions, which may be due to anisotropic strain relaxation in the Si1-xGex buffer layers.