Quantum confinement induced by strain relaxation in an elliptical double-barrier Si∕Si_xGe_1−x resonant tunneling quantum dot

Starting with a double-barrier p-Si∕Si_0.75Ge_0.25 resonant tunneling heterostructure, we fabricated sub-100-nm elliptical quantum dots. Sidewall strain relaxation in the Si_xGe_1−x layer induces a lateral confining potential that quantizes heavy hole (HH) and light hole (LH) states in the SiGe quantum well, leading to fine structure in the HH-LH I(V) resonant tunneling curves at low temperature. In this paper, we present the magnetotunneling I(V,B) characteristics of heavy holes and light holes in magnetic fields B parallel to the tunneling current. From the evolution of the fine structure, we observe the competition between the strain-induced lateral confinement potential and the magnetic confinement, from which we infer lateral potentials of HH and LH different from those of previously studied cylindrically symmetric dots. The experimental data are in qualitative agreement with inhomogeneous strain-induced HH and LH potential obtained via a full three-dimensional finite-element strain simulation.