Strain Engineering of Ge Quantum Wells in Planar Ge/Si _{1 − x} Ge _x Heterostructures

Abstract Germanium (Ge) has been identified as a good candidate among semiconductor‐based materials for quantum applications. One of the main reasons lies in the long coherence time of spins of localized holes, its ability to host superconducting pairing correlations, and compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology. Recent studies reveal how the growth of strained germanium quantum wells (QWs) embedded in silicon‐germanium (SiGe) barriers is crucial to enhance charges' mobility in this system. In this work, a study is presented of the distribution of in‐plane and out‐of‐plane strain in germanium quantum wells embedded in Si _{1 − x} Ge _x barriers in order to engineer strain in the quantum well, thus tuning the charge mobility therein for quantum computing purposes. Therefore, experimental techniques such as Raman spectroscopy, transmission electron microscopy (TEM), and geometric phase analysis (GPA) are combined with Schrödinger–Poisson solver simulations in order to find the optimal quantum well thickness and silicon (Si) content in the Si _{1 − x} Ge _x barriers to enhance and control electrical properties in Ge/SiGe planar heterostructures.