Magneto-tunneling of holes in Si/Si1-xGex/Si double barrier structures.

Resonant and non-resonant tunneling processes in p-type Si/Si$\sb{\rm 1-x}$Ge$\sb{\rm x}$/Si double barrier structures were investigated at cryogenic temperatures in both planar and perpendicular magnetic fields. A differential conductance measurement technique was devised to observe non-resonant tunneling features superimposed on a rapidly increasing current background. An additional resonant feature was observed at high bias voltage and is attributed to tunneling of holes from the two-dimensional heavy hole subband in the emitter to a third quasi-bound state in the quantum well. Experimental evidence for non-resonant tunneling processes is presented for the first time in p-type double barrier structures. Inter-Landau level transitions between the emitter and the quantum well occur either elastically by scattering from impurities or inelastically with the emission of optical phonons. Both processes have been observed in our samples. Data above 4.2 K suggest that tunneling processes also take place from the three-dimensional valence band edge states in the emitter. A novel spectroscopy of the quasi-bound states in the well was performed by measuring the shift in energy of the resonant tunneling features as a function of applied planar magnetic field