Engineering and control of advanced optoelectronic materials for applications in quantum devices

The challenges introduced by the miniaturization and growing demands of modern computing technology require advanced materials solutions that are both tunable and easy to characterize. As applications become more specialized thanks to improvements in fabrication capabilities, the complexity of these synthesized materials and devices increases dramatically, which demands a firm understanding of the dominant underlying physics. In this dissertation, we investigate three different artificially structured materials used in applications supporting quantum devices through optical and electronic techniques. In the first case, second harmonic generation (SHG) in reflection characterized the second order nonlinear susceptibility X⁽²⁾ in strained thin film Ba₁₋ₓSRₓTiO₃ alloys as a function of thickness and composition. We found that alloys containing a proportion of Sr between 10 and 40% were successfully able to sustain an out-of-plane polarization that allows them to be interfaced with existing Si platforms without suffering adverse interfacial defects. In the second study, we invoked azimuthal angle-dependent SHG to indirectly probe X⁽²⁾ of digital alloy-grown multiple quantum well structures composed of InAs and AlSb. We used an optical response matrix to model the multilayered structure and found that the consideration of complex X⁽²⁾ phase interference was crucial to accurately represent the data. The resulting model yielded a value of X⁽²⁾MQW 4 times greater than that of its bulk constituents, which opens possibilities for engineering more complex structures for optoelectronic applications. Finally, the rapid thermal anneal-driven electrical activation of Ga dopants implanted in Ge was evaluated using depth profiling and surface characterization techniques. By sufficiently healing lattice damage meanwhile avoiding dopant loss induced by annealing at temperatures too high, we found a usable range of anneal temperatures inducing electrical activation of dopants up to 64%. These findings have strong implications for the success of acceptor-based nuclear spin qubits in Ge, which hosts advantages to the quintessential Si in potential quantum computing platforms. Subsequently, we present preliminary spectral photoconductivity measurements of bound excitons in Ga-doped Ge as a viable path towards the development of a nuclear spin-based quantum computer. The works described here illuminate some of the ways that properly characterized solid state systems can be leveraged to support the next generation of modern computing devices.Physic