Quantum confinement induced by strain relaxation in an elliptical double-barrierSi∕SixGe1−xresonant tunneling quantum dot

Abstract

Starting with a double-barrier p-Si/ Si 0.75 Ge 0.25 resonant tunneling heterostructure, we fabricated sub-100-nm elliptical quantum dots. Sidewall strain relaxation in the Si x Ge 1−x layer induces a lateral confining potential that quantizes heavy hole ͑HH͒ and light hole ͑LH͒ states in the SiGe quantum well, leading to fine structure in the HH-LH I͑V͒ resonant tunneling curves at low temperature. In this paper, we present the magnetotunneling I͑V , B͒ 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 straininduced 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 threedimensional finite-element strain simulation.