Engineering Light-Hole Quantum States in an Optically Active Group IV Low Dimensional System

Hole spins have attracted a great deal of attention because of their reduced coupling to the nuclear spin bath. However, most of experimental investigations on 2D gas systems have so far focused on heavy-hole states (HH). This is attributed to the nature of the heterostructure currently exploited, where compressive strain lifts the valence band degeneracy and leaves HH states energetically well above the light-hole (LH) states. However, the ability to exploit LH states will be a powerful paradigm beneficial for quantum information technologies, as the orbital angular momentum of LH states makes them more powerful and versatile. To harness these largely unexplored advantages of LH states, we present a new low-dimensional system consisting of highly-strained Ge quantum well (QW) grown on silicon wafers using GeSn as barriers. To quantify the effect of the LH confinement as well as the LH-HH mixing, several spectroscopic techniques were used to identify the LH confined states in the Ge well. The obtained heterostructure shows optical transitions that can be modulated in the midinfrared range. This ability to engineer quantum structure where LH is the ground state in an optically active group IV platform lays the groundwork for a new class of Si-compatible quantum technologies.