Nanoscale Optical & Spin Spectroscopy to Probe Semiconductor & Quantum Devices
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As further shrinking the silicon transistor faces fundamental material limits, scaling computing devices going forward involves a multifaceted approach that includes not just new nanoscale transistor architectures, but also new materials like two-dimensional (2D) semiconductors and new paradigms like quantum computing. Each of these paths presents a materials challenge requiring an exceptional degree of control over material disorder at the nanometer and atomic scales. After outlining these challenges in the context of semiconductor transistors and superconducting qubits, this thesis details optical and spin spectroscopy techniques aimed at connecting fundamental physics to device performance across three technologically critical areas: 2D semiconductors for future transistors, wide-bandgap semiconductors for power electronics, and superconducting qubits for quantum computing. The first of these techniques measures wafer-scale spatial disorder in 2D transition-metal dichalcogenide (TMD) semiconductors in the context of extremely scaled (<10 nm) transistors by leveraging the many-body physics of exciton-trion states in these materials. Second, this thesis describes interface-sensitive electron spin resonance (iESR) spectroscopy as a means to measure surface defects in semiconductors and superconductors, with an aim to discern material sources of loss and noise in semiconductor devices and superconducting qubits. Finally, this thesis describes the use of broadband, ultrafast optical spectroscopy to simultaneously measure the time-resolved spectrum and dynamics of multiple defect charge states at sub-nanosecond time scales, revealing mechanisms of charge trapping and material breakdown in wide-bandgap semiconductors.