Key Takeaways & Executive Findings
- •• Decreasing V thickness in V/Al/Ti/Au electrodes promotes Al diffusion to n-AlGaN surface, enhancing VN formation and local electron concentration, thereby reducing specific contact resistivity. • Increasing Al thickness inhibits Au diffusion to the n-AlGaN surface, suppressing Schottky barrier rise and further improving contact performance. • Optimized electrode stack V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm) achieves a record-low specific contact resistivity of 7.30 × 10−4 Ω·cm2 on n-Al0.81Ga0.19N. • Application of the optimized n-electrode reduces the operating voltage of a 233.5 nm far-UVC LED, demonstrating practical viability.
Abstract
AlGaN-based LEDs with peak wavelength below 240 nm (far-UVC) pose no significant harm to human health, thus highlighting their broader application potential. While, there is a significant Schottky barrier between the n-electrode and Al-rich n-AlGaN, adversely impeding electron injection and resulting in considerable heat generation. Here, we fabricate V-based electrodes of V/Al/Ti/Au on n-AlGaN with Al content over 80% and investigate the relationship between the metal diffusion and contact properties during the high-temperature annealing process. Experiments reveal that decreasing V thickness in the electrode promotes the diffusion of Al towards the surface of n-AlGaN, which facilitates the formation of VN and thus the increase of local electron concentration, resulting in lower specific contact resistivity. Then, increasing the Al thickness inhibits the diffusion of Au to the n-AlGaN surface, suppressing the rise of Schottky barrier. Experimentally, an optimized n-electrode of V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm) on n-Al0.81Ga0.19N is obtained, realizing an optimal specific contact resistivity of 7.30 × 10−4 Ω·cm2. Based on the optimal n-electrode preparation scheme for Al-rich n-AlGaN, the work voltage of a far-UVC LED with peak wavelength of 233.5 nm is effectively reduced.
1. Introduction
Recently, deep ultraviolet (DUV) light-emitting diodes (LEDs) have garnered huge attention due to their potential to replace traditional mercury lamps in various applications including sterilization, water purification, photolithography, medical treatment[1−5]. Studies have shown that LEDs with emission wavelengths below 240 nm (far-UVC) pose no significant harm to human, thus highlighting their broader application potential[6−9]. AlGaN is a preferred material for the fabrication of far-UVC LEDs because its bandgap can be adjusted from 3.4 to 6.2 eV by altering the Al content and both n- and p-type doping have been achieved[10−17]. To prevent absorption of the light generated from the active region with wavelength below 240 nm, the Al content in the n-AlGaN should exceed 80%[18, 19]. This extremely high Al content causes two serious issues. On the one hand, with Al content increasing, the electron affinity gradually diminishes to ev...
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Jiale Peng, Ke Jiang, Shanli Zhang, Jianwei Ben, Kexi Liu, Ziyue Qin, Ruihua Chen, Chunyue Zhang, Shunpeng Lv, Xiaojuan Sun, Dabing Li (2025). Reducing specific contact resistivity of V/Al/Ti/Au n-electrode on n-AlGaN with Al content over 80% for far-UVC LEDs. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25010026
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Frequently Asked Questions
What is the main challenge in fabricating n-electrodes for Al-rich n-AlGaN?
The main challenge is the significant Schottky barrier between the n-electrode and Al-rich n-AlGaN, which impedes electron injection and leads to heat generation, increasing the difficulty of achieving low-resistance ohmic contacts.
How does reducing V thickness improve contact resistivity?
Reducing V thickness promotes the diffusion of Al towards the n-AlGaN surface, facilitating the formation of VN. This increases the local electron concentration, thereby lowering the specific contact resistivity.
What is the optimal electrode structure reported in this study?
The optimal n-electrode structure is V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm) on n-Al0.81Ga0.19N, achieving a specific contact resistivity of 7.30 × 10−4 Ω·cm2.
How does increasing Al thickness affect the contact properties?
Increasing Al thickness inhibits the diffusion of Au to the n-AlGaN surface, which suppresses the rise of the Schottky barrier, thereby improving the contact performance.
What is the practical impact of this research on far-UVC LEDs?
The optimized n-electrode reduces the operating voltage of a 233.5 nm far-UVC LED, demonstrating its potential to enhance the efficiency and performance of far-UVC LEDs for applications like sterilization and water purification.
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