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/${\mathrm{Si}}_{0.8}$${\mathrm{Ge}}_{0.2}$ resonant tunneling structures with different middle barrier widths (L=10, 20, and 30 Å) for T≤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-HH coupling with the addition of weaker HH-LH coupling for the narrowest middle barrier width, L=10 Å. We also present measurements displaying the HH-LH interaction strength dependence on high magnetic fields parallel to the current, ${\mathit{B}}_{\mathrm{\parallel }}$. The weak HH-LH interaction quenches as ${\mathit{B}}_{\mathrm{\parallel }}$ approaches 10 T. © 1996 The American Physical Society.