Magneto-Transport Measurements on Si/Si 1−x Ge x Resonant Tunneling Structures

We have investigated magneto-transport properties of differently strained Si/ Si 1−x Ge x resonant tunneling devices. The built-in strain was either put in the Si layers, by means of a thick., relaxed Si 1−x Ge x buffer layer, or in the Si 1−x Ge x layers, in which case all Si 1−x Ge x layers were grown below the critical thickness, and a Si 1−x Ge x spacer layer with graded Ge content was used. Magnetic fields parallel to the interface have been employed to probe the in-plane dispersion in the quantum well. This is used to study the effect of band-mixing in the two strain configurations. A field perpendicular to the interface resolves some Landau level splitting. Most strikingly, however, is the similarity in the spectra with the case when the magnetic field is applied parallel to the interfaces. This indicates broadening of the levels, possibly due to scattering, and the importance of 3-dimensional band structure effects.