Stephen Schaefer Email & Phone Number

Berlin, De

Tucson, Az, Us

Golden, Colorado, United States

Studied the growth and physical/electrical properties of ultrawide bandgap materials including gallium oxide (Ga2O3) and its alloys by grown by molecular beam epitaxy (MBE). I developed a novel cyclical growth/etch-back MBE methodology that increased experimental throughput by over 6× and single-crystal substrate utilization by over 40×, and demonstrated the first successful synthesis of the monoclinic quaternary alloy (AlxGa1-x-yIny)2O3. I installed and commissioned a new MBE chamber for growth of novel ternary metal nitrides such as MgMoN2 and ZnMoN2, among others. Additionally, I was involved in proposal efforts for adaptive computing & machine learning enabled high throughput materials development, and in road mapping efforts for next-generation power electronics operating at high voltages and temperatures. I was actively involved in laboratory activities including installation, commissioning, and maintenance of various UHV systems, design & solid modeling of custom research solutions, and physical/chemical/optical characterization techniques.

Tempe, Arizona, United States

Studied the growth and properties of group II-VI and group-IV semiconductor materials for solar cell and infrared photodetector applications. Our research group investigated the MBE growth of bulk CdSe and MgCdTe/CdTe heterostructures for use as the top cell in tandem II-VI/Si solar cells. Additionally, our research group was part of a MURI collaboration with the Air Force Office of Scientific Research (AFOSR) and other academic institutions investigating the growth and properties of group-IV SiGeSn alloys for mid- and long-wave infrared photodetectors. Additionally, I modeled & analyzed type-II asymmetric quantum well structures with high second-order nonlinear susceptibility. I was actively involved in laboratory activities including MBE growth, physical and optical characterization, and equipment maintenance/improvement, in addition to actively participating in writing proposals for CdSe based solar cells, second-order nonlinear materials research, and a novel real-space carrier separation architecture for infrared detectors.

Tempe, Arizona, United States

Studied the growth and properties of group III-V semiconductor materials for infrared optical applications. Specifically, our group investigated the properties of materials incorporating the atom bismuth (Bi) grown using molecular beam epitaxy (MBE), a high-vacuum technique which allows growth of high-quality single-crystal materials at non-equilibrium concentrations. MBE-grown samples are characterized using a variety of structural, chemical, and optical techniques. These include x-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy, spectroscopic ellipsometry, and Rutherford back-scattering, among others.

Marana, Arizona, United States

Participated in a research and development program on permanent-magnet synchronous motors and design of motor controllers. This included design of novel power amplifier circuit topologies and implementation of closed-loop feedback and feedforward control systems. Performed custom electronics circuit and chassis design.

Tucson, Arizona, United States

Supported a custom RF plasma power supply design and developed a novel high voltage pulsed plasma power supply prototype.

Doctor Of Philosophy - Phd, Electrical And Electronics Engineering

Studied the growth and properties of group III-V semiconductor materials for infrared optical applications. Specifically, our group.

Master Of Science - Ms, Electrical And Electronics Engineering

Studied the growth and properties of group III-V semiconductor materials for infrared optical applications. Specifically, our group.

Bachelor Of Science - Bs, Electrical And Electronics Engineering