Date: Friday, October 4, 2024

Time:  4:30 PM-6:00 PM

Location: CHTM, Room 103

Dissertation Committee:

Distinguished Professor Marek Osinski, (Committee Chair), Physics
Dr. Sadhvikas J. Addamane, Sandia National Labs & CINT
Professor Payman Zarkesh-Ha, ECE
Dr. Tzu-Ming Lu, Sandia National Labs

Abstract:

After its humble beginnings as the first transistor, germanium was supplanted by silicon as the dominant semiconductor for transistor technology. Ironically, due to technological advancements that silicon has brought, germanium has resurged as a material platform for the post-Moore era as silicon transistors are reaching their physical limits. Not only is it attractive as a replacement for CMOS and silicon photonic technologies with its silicon foundry compatibilities, but germanium also shows promise for a paradigm shift in transistor and computing technologies with spin field-effect transistors and spin qubits using gate-defined quantum dots. However, for these technologies to be successful, it must be shown that high-quality material can be grown at large-scales and how fabrication processes affect material quality and device performance.

In this work, we partnered with a commercial silicon-germanium epitaxy supplier to obtain high-quality, shallow and undoped germanium quantum wells on a 200 mm silicon wafer platform. High-crystalline quality was conveyed using structural characterization techniques including x-ray diffraction, secondary ion mass spectroscopy, high-resolution scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. Hall bar devices were fabricated on single quantum wells using a variety of surface preparations. Together, structural characterization and low-temperature Hall measurements revealed how surface preparation can be used to tune transport properties while still maintaining peak mobilities around 10⁵ cm²V^-1s^-1. Manganese-germanide spintronic contacts were directly integrated into the germanium quantum wells via solid-state reaction. The quality of the contacts was explored using structural characterization and by creating Schottky diodes, transfer length method devices, and Hall bars for electrical characterization. Finally, we used structural, electrical, and optical characterization to show that high-quality double quantum wells can be grown indicating possibilities for novel devices using multiple quantum wells.

Biography:

Troy Hutchins-Delgado is a member of Prof. Marek Osinski’s group and a PhD candidate in the Optical Science and Engineering program at the University of New Mexico. Troy earned a B.S. in Physics and a B.S. in Electrical Engineering from North Carolina State University in 2016. Troy earned his M.S. in Optical Science and Engineering in 2019 under Prof. Osinski where he performed fabrication and cryogenic characterization of III-V laser devices. Troy has been a graduate intern at Sandia National Laboratories since August 2019 working under Dr. Tzu-Ming Lu. Troy’s work at Sandia has been on characterizing group-IV material platforms for both classical and quantum spintronic applications. Troy performs most of his work at the Center for Integrated Nanotechnologies (CINT) using the clean room to fabricate gate-defined quantum dots and basic testing devices. Upon graduation, Troy will be continue working with Sandia as a post-doctoral researcher studying the origins of noise in spin qubit devices.