Recently, a significant advancement in the study of carrier dynamics in wide-bandgap nitrides has been made by Professor Suhuai Wei, Dean and Chair Professor of the School of Physics at EIT Ningbo, in collaboration with the team of Researchers Zhiming Shi, Xiaojuan Sun, and Dabing Li from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences. They proposed a novel strategy utilizing interface defect engineering to accelerate electron cooling, effectively addressing the long-standing issue of asymmetric carrier injection that plagues the efficiency of nitride-based ultraviolet light-emitting diodes. This work, entitled "Overcoming asymmetric carrier injection in III-nitride light-emitting diodes through defect engineering", was published in the prestigious physics journal Physical Review Letters on July 8, 2025.
AlGaN-based UV LEDs are core components for next-generation applications such as high-density optical storage, sterilization, and air purification. A key factor limiting their efficiency lies in the asymmetry of electron and hole cooling rates: the energy relaxation process for electrons is significantly slower than that for holes, leading to low radiative recombination efficiency. Conventional approaches often involve introducing an electron blocking layer (EBL) to enhance electron injection efficiency. However, these methods face challenges such as complex design, additional potential barriers, and material compatibility issues, making it difficult to fundamentally optimize carrier dynamics.
Based on their analysis of nitride band structures and carrier dynamics, the teams led by Professor Suhuai Wei and Researchers Zhiming Shi, Xiaojuan Sun, and Dabing Li proposed for the first time to effectively enhance the electron cooling rate by controlling nitrogen vacancy defects at the GaN/AlN quantum well interface. These defect states act as intermediate energy levels, significantly strengthening electron-phonon interactions and thereby accelerating electron cooling towards the conduction band minimum. First-principles calculations indicate that this strategy can shorten the electron cooling time by more than an order of magnitude, effectively achieving a dynamic balance with the hole cooling rate and substantially improving luminescence efficiency. Compared to traditional EBL structures, this method enables precise control of electron dynamics without the need for additional structural design. This research also expands the boundaries of semiconductor defect physics, systematically validating the beneficial role of defects in regulating device performance, challenging the traditional perception of defects as solely detrimental. It provides theoretical support and new ideas for defect engineering in next-generation electronic and optoelectronic devices.
The results deepen the understanding of the interaction mechanisms between carrier dynamics and defects in wide-bandgap nitrides, holding significant importance for enhancing the internal quantum efficiency of UV LEDs and realizing high-performance optoelectronic devices.
The first author of the paper is Ph.D. candidate Yuxin Yang from CIOMP, Chinese Academy of Sciences. The corresponding authors are Researcher Zhiming Shi, Professor Suhuai Wei, Researcher Xiaojuan Sun, and Researcher Dabing Li.
