RESONANT TUNNELING OF HOLES IN SI/GEXSI1-X

The compressional strain in GexSi1-x grown on Si moves the light-hole (LH) band down and the heavy-hole (HH) band up, while the tensile strain in Si grown on GexSi1-x moves the LH band up and the HH band down. In the tunneling structure of Si/GexSi1-x grown on a Si substrate with a GexSi1-x or Si buffer layer, the band offsets of LH and HH are then changed depending on the strain in Si/GexSi1-x, which is influenced by the lattice relaxation of the buffer layer. In this work the Fermi level E(f) of the tunneling structure is investigated from the energy band structure calculations to provide information for tunneling current calculations and peak identification in comparison with experimental I-V spectra. When a Si buffer layer is used, only the HH band of the GexSi1-x spacer is found to be filled so that the tunneling current is HH characteristic. With a GexSi1-x buffer layer both LH and HH contribute to the total tunneling current. The effective mass approximation is also investigated for Si/GexSi1-x tunneling structures and a quasiparticle (HH, LH, and the spin-orbital splitoff) tunneling picture is justified for theoretical analysis.