Grant: Research Tools and Instruments

Sn-containing group IV alloys are an emerging class of semiconductors attracting significant interest for achieving the long-sought monolithic integration of electronics and photonics. The recent availability of nonequilibrium growth protocols has enabled the circumvention of major thermodynamic constraints that hampered the development of these materials for decades, resulting in innovative quantum-engineered heterostructures and their integration into a wide range of devices. Our group is among the few worldwide with the capability to epitaxially grow device-quality group IV heterostructures, controlling the growth kinetics to achieve high crystalline quality, metastable, diamond-structure materials. From a fundamental perspective, the bandgap directness and tunability across the infrared spectrum, strong spin-orbit coupling, hole spin quiet quantum environment, and the presence of a semiconductor-semimetal transition make these alloys uniquely suited for investigating and engineering a variety of critical quantum processes on a silicon-compatible, scalable platform. Additionally, these group IV elements possess several stable isotopes (e.g., ²8Si, ²?Si, 3°Si, 7°Ge, 7²Ge, 73Ge), offering added flexibility to tailor their fundamental properties by leveraging isotope effects on nuclear spin, electronic structure, lattice disorder, and phonon scattering. This unique combination of bandgap and isotope engineering enables the design and development of innovative quantum structures such as single-photon emitters, spin qubits, and quantum memories. This project aims to exploit these potentials and implement novel heterostructures to investigate and eventually control hole spin, single photons, photon-spin interactions, and topological phases. Achieving these objectives requires enhanced characterization capabilities to address current scientific challenges that limit our ability to optimize and control the fundamental behavior of group IV semiconductors by fostering a deep understanding of the interplay between atomic-level structure and the material and device optical and electronic responses. While we have the setups needed to conduct these studies, the lack of low-temperature capabilities currently limits both the scope and depth of our scientific inquiries. To address this, we are requesting a closed-cycle cryostat specifically designed for temperature-dependent spectroscopic studies and optoelectronic characterization. The cryostat will be central to various setups, allowing us to study basic properties (such as bandgap energy, electronic transitions, quantum confinement, and defects) of group IV heterostructures to support the design and fabrication of integrated devices for applications in sensing, imaging, and free-space communication.