Resonant-tunneling spectroscopy of coupled hole subbands in strained Si/SiGe triple-barrier structures

We examine transport of holes in asymmetric triple-barrier p-Si/Si0.8Ge0.2 resonant tunneling structures with different middle barrier widths (L=10, 20, and 30 Angstrom) for T less than or equal to 4.2 K. The two-dimensional (2D) heavy-hole (HH) and light-hole (LH) subbands in each of the two quantum wells interact through interwell tunneling, resulting in 2D double-well subbands. We identify resonances corresponding to tunneling transitions through these double-well subbands using a simple wave-function formalism. The observed resonances correspond to strong HH-LH coupling with the addition of weak;er HH-HH coupling for the narrowest middle barrier width, L = 10 Angstrom. We also present measurements displaying the HH-LH interaction strength dependence on high magnetic fields parallel to the current, B-parallel to. The weak HH-LH interaction quenches as B-parallel to approaches 10 T.