UIUC Achieves Record Modulation Bandwidth of 2.75 GHz for GaN Blue Micro-LEDs
The findings establish a systematic scaling roadmap for micro-emitters, demonstrating their potential to replace conventional copper electrical links and overcome energy consumption and bandwidth bottlenecks in data centers and next-generation AI computing systems.
As demand for artificial intelligence and high-performance computing continues to surge, conventional copper-based data interconnects are struggling to keep pace. They consume substantial amounts of power, generate considerable heat and cannot sustain the data rates required by emerging applications. Optical interconnects offer a promising alternative, but developing compact, high-performance light sources remains a challenge.
Micro-LED arrays could provide a solution by enabling massively parallel optical data links with a compact footprint and the potential for scalable integration. Such links could support high-bandwidth communication while reducing energy consumption.
Led by UIUC professor Can Bayram, the research team designed and fabricated blue micro-LEDs across nearly two orders of magnitude in size, with diameters ranging from 100µm to just 2µm.
The analysis identified the optimal device dimensions and the physical limitations that must be addressed to improve performance further. The researchers found that scaling down to the single-digit micrometer range is essential. Their 5µm-diameter device achieved a record modulation bandwidth of 2.75GHz while maintaining excellent linearity and stability at extreme current densities of 15kA/cm².
“By unifying modulation, linearity and impedance measurements across such a vast scaling range, we have for the first time established a device-level roadmap for micro-LED transmitters in high-bandwidth optical interconnects,” Bayram said.
The research not only establishes a new performance record but also provides a framework for developing dense, low-energy optical communication channels in a compact form factor. According to Bayram, this approach could significantly reduce the packaging complexity of future optical networks designed for AI applications.
The technical analysis included Smith chart measurements to assess radio-frequency power delivery. These measurements helped explain why conventional, larger micro-LEDs with diameters of around 100µm have limited bandwidth. The main constraint is junction capacitance, which restricts their high-frequency performance.
Reducing the device diameter below 20µm significantly lowers this capacitance, enabling substantially higher operating speeds. However, further miniaturization introduces a different set of challenges.
Below 5µm, contact resistance and current-spreading resistance increase, creating an impedance mismatch with standard 50Ω radio-frequency systems. This limits the benefits of additional size reductions.
The researchers identified optimization of the p-type electrical contact and improvements to contact-pad design as important next steps. Addressing these issues could enable even higher bandwidths in future micro-LED transmitters.
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