Beaming with possibilities

Yong-Hang Zhang pushes the boundaries of solar and infrared technology with semiconductor design breakthroughs

An Arizona State University researcher’s groundbreaking developments — built on a semiconductor-fabrication technology developed in the 1960s — address current solar cell challenges and may open new possibilities for power electronic technologies.

Those developments are rooted in a process known as molecular beam epitaxy, or MBE, a technique that revolutionized semiconductor fabrication when it was introduced at Bell Telephone Laboratories in the 1960s. Used to deposit single-crystal materials in atomically thin layers, MBE plays a key role in the evolution of nanotechnology and continues to underpin advances in high-performance semiconductor devices.

Yong-Hang Zhang, a professor of electrical engineering in the School of Electrical, Computer and Energy Engineering, part of the Ira A. Fulton Schools of Engineering at ASU, is a well-established researcher in the field of MBE and its practical applications for modern electronics. In a career spanning over 40 years, he has pushed the boundaries of solar energy and infrared detection with innovations that solve long-established scientific challenges in semiconductor materials and devices.

Zhang and his team are unlocking cleaner, cheaper and more reliable energy technologies by inventing new methods to build solar cells without certain types of doping, such as p-type doping — which involves adding impurities to a material to control its electrical conductivity — and by creating highly efficient materials.

In August, Zhang received the 2025 Art Gossard MBE Innovator Award at the 39th North American Conference on Molecular Beam Epitaxy for his pioneering contributions to MBE, including breakthroughs in type-II superlattice infrared detectors and high-efficiency solar cells. His innovations have been adopted for defense and commercial applications by many U.S. companies like Raytheon, Teledyne and HRL, as well as international companies like Hamamatsu in Japan and Vigo in Poland.

The award, first established in 2003, recognizes individuals whose innovative work has significantly advanced the field of MBE.

Zhang says the recognition also highlights the impact of ASU’s MBE Optoelectronics Group, which he leads.

“Receiving this recognition humbles me, and I would like to express sincere gratitude to my students, postdoctoral researchers and collaborators at ASU and other institutions worldwide,” Zhang says. “Their dedication, passion and invaluable contributions have made everything possible and without them, the work we’ve accomplished over the past decades would not have been possible.”

Zhang’s research on the growth, fabrication and characterization of novel optoelectronic materials and devices centered on narrow-gap semiconductors, infrared detectors and solar cells has resulted in him being named Fellow in the Optical Society of America, now recognized as Optica, and Fellow of the Institute of Electrical and Electronics Engineers, or IEEE, in 2014 and 2015, respectively.

Yong-Hang Zhang, center, receives the 2025 Art Gossard MBE Innovator Award from NAMBE Advisory Board Treasurer Maria Tamargo, center right, with conference chairs and members of the ASU MBE Optoelectronics Group and collaborator from the Paul-Drude-Institute for Solid State Electronics in Berlin. The achievement was celebrated at the 39th North American Conference on Molecular Beam Epitaxy held in Albuquerque. Photo courtesy of ASU MBE Optoelectronics Group

Research on the rise

In addition to receiving the prestigious award, Zhang recently spearheaded research featured on two consecutive covers of the Wiley publication Solar RRL, high-impact journal dedicated to showcasing scientific discoveries and technology development that demonstrate new methods and breakthroughs in solar energy and device applications.

In the first paper, Zhang and members of his MBE Optoelectronics Group invented a way to overcome cadmium telluride’s limitation of being difficult to dope p-type by using precise control of atomic-scale interfaces, made possible through MBE technology. Their ideas have been confirmed through a seamless collaboration with ASU Regents Professor David Smith and Lynn H. Matthias Professor in Engineering Zhenqiang (Jack) Ma from the University of Wisconsin at Madison.

Cadmium telluride is a semiconductor material heavily used in thin-film solar cells for its highly efficient light absorption, which enables thinner and more affordable solar panels. This technology also has potential for use in space applications on satellites and rovers.

Zhang says that solar industry partners have dedicated large amounts of money and research efforts towards solving the issues with doping in thin-film solar cells, but were unsatisfied with those explored approaches.

He adds that government agencies like the U.S. Department of Energy and National Renewable Energy Laboratory, or NREL, deploy programs that encourage academia to help tackle challenges faced by industry — in this case solar cell doping.

“We have broadened the scope of collaboration with NREL to apply the idea to other materials systems and advanced material characterization,” he says.

Zhang says research results have led to a provisional patent application and potential approaches beyond solar cells in areas like power electronics.

The June and July 2025 issues of the Solar RRL journal featuring published research of Zhang and his team’s work using molecular beam epitaxy to discover a new way to overcome the doping challenge and to make thin-film solar cells more efficient with potential lower cost. Cover photos courtesy of ASU MBE Optoelectronics Group

Zhang and his team’s second paper in Solar RRL examines an industry challenge regarding specially designed alloys used in thin-film solar cells — balancing lattice structure, defects and bandgap tuning to create better-performing devices.

The researchers deployed MBE technology to examine how adjusting the chemical composition and crystal structure could potentially improve the thin-film solar cell performance.

“This research offered some very useful information and insights for industry to improve their processes and invent new approaches,” he says. “Having research featured on the cover of back-to-back publications is rare and showcases the important work of our research team and the continued promise of MBE to examine and solve problems.”

Zhang underscores the importance of both papers as examples of use-inspired research to better develop useful technology and tools for industry and improve quality of life for the public with practical products.

The consecutive journal cover features highlight the broad applications of Zhang and his team’s research, potentially accelerating progress in the development of affordable, next-generation solar and power devices.

Importance of interdisciplinary people and places

Individual accolades aside, Zhang acknowledges that high-quality facilities and interdisciplinary collaboration at ASU, involving electrical engineering and physics departments in this case, as a key factor in his work, producing impactful research and rethinking microelectronics advances at ASU and elsewhere.

Zhang is the founding director of ASU’s Center for Photonics Innovation, or CPhI, which includes the MBE Optoelectronics Group. Created in 2005, the CPhI assembles a large group of faculty members across several scientific disciplines to foster new ideas and execute collaborative research.

“We have been successful because we work in a very collaborative environment, built on decades of complementary expertise,” Zhang says. “Our students are constantly engaged, and the university strongly supports this kind of interdisciplinary teamwork.”

From 2016 to 2019, Zhang also served as director for the ASU NanoFab, which is a core research facility that supports device fabrication, an essential part of Zhang’s current work.

“The tools and resources available in specialized labs and ASU core facilities such as the NanoFab, the Ultrafast Laser Facility, as well as the Eyring Materials Center play a critical role in our research,” Zhang says. “ASU has invested a lot of capital in these facilities, and our research shows that the investment is paying off.”

In the future, Zhang looks forward to continuing his interdisciplinary efforts and working with the MBE Optoelectronics team to address other challenges. He notes that the same ideas can be readily extended to other semiconductors with doping issues, such as III-nitrides, oxides, diamond and mercury cadmium telluride.

“These materials have a very broad application ranging from solar cells and infrared detectors to high power and high temperature electronic devices, so there are many interesting possibilities,” he says.