Materials with an indirect bandgap are generally regarded as poor candidates for light-emitting devices because electrical charge tends to lose energy before producing light. Researchers at Lund University have now demonstrated that these materials can instead play a different, and potentially valuable role. By engineering branched semiconductor nanowires, they showed chare carriers diffuse from an indirect-bandgap nanowire core material to direct-bandgap nanowire branches grown on the core, where light is emitted by recombination of the injected electron and holes.
The study, recently published in Nano Research on July 16, 2026, presents a new design for nanowire light-emitting diodes (LEDs) that separates charge transport from light generation. Rather than forcing the entire device to emit light, the researchers intentionally suppressed light emission in the nanowire core while directing electrons and holes toward nanoscale branches grown on the indirect band gap nanowire core to optimize radiative recombination in the branches.
"Indirect-bandgap semiconductors have traditionally been regarded as poor materials for light-emitting devices, "said Magnus T. Borgström, professor in the Division of Solid State Physics at the Department of Physics, Lund University. "Instead of trying to make the indirect-bandgap material emit light efficiently, we designed it to transport charge carriers into nanoscale branches that are much better light emitters. This allows us to separate charge transport from light generation in a completely new way."
The researchers fabricated arrays of branched gallium indium phosphide (GaInP) nanowires, referred to as "nanotrees." Each nanowire consists of a vertical core surrounded by many nanoscale branches. By carefully choosing the semiconductor composition, the core was engineered to have an indirect bandgap while the branches retained a direct bandgap, creating an energy landscape that naturally drives charge carriers toward the branches.
Electroluminescence measurements confirmed that the indirect-bandgap design dramatically changed where light was produced. Compared to similar devices built on direct-bandgap cores, the new architecture strongly suppressed light emission from the core while enhancing emission from the branches.
Beyond demonstrating a new LED architecture that can enhance light extraction, the work suggests a broader design principle for semiconductor devices. By separating charge transport and light generation, future nanowire LEDs may lead to better control over spatial light emission and improve light extraction efficiency.
"This work demonstrates that indirect-bandgap materials can become an active part of light-emitting devices when integrated with nanoscale bandgap engineering, according to Yue Zhao. "We believe this LED architecture could inspire new nanowire optoelectronic devices in which carrier transport and light emission are designed independently."
The researchers plan to further optimize the device by improving electrical contacts and surface passivation, while exploring additional material combinations that could extend the concept to other wavelengths and future nanophotonic applications.
Manuscript contributors include Yue Zhao, Kristi Adham, and Haonan Chen and Magnus T. Borgström who are affiliated with the Division of Solid State Physics, Department of Physics, Lund University, Sweden. Haonan Chen and M. T. Borgström are also affiliated with the Wallenberg Initiative Materials Science for Sustainability (WISE), Department of Physics, Lund University, Sweden. Kristi Adham is currently with AWA Sweden AB, Lund, Sweden.
This work was supported by the Swedish Research Council, the Swedish Energy Agency, the European Union's Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant Agreement No. 945378, the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation, the Royal Physiographic Society in Lund, and Myfab.
About the Authors
Dr. Magnus T. Borgström is a Professor in the Division of Solid State Physics, Department of Physics, Lund University, Sweden, where he leads a research group within NanoLund. His research focuses on the epitaxial growth of semiconductor nanostructures, with particular emphasis on III–V nanowires for next-generation optoelectronic devices. His group develops nanowire-based tandem solar cells, explores hybrid tandem architectures combining nanowires with perovskite materials, and investigates novel nanowire light-emitting diode concepts based on charge carrier diffusion to improve light extraction efficiency. For more information, visit his research profile: https://portal.research.lu.se/sv/persons/magnus-borgstr%C3%B6m .
DOI Link:
https://doi.org/10.26599/NR.2026.94908799
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
Nano Research
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