Few research collaborations in the semiconductor field have been as impactful as the partnership between Nitride Semiconductors and the Institute of Nitride Semiconductors at Tokushima University. The collaboration united the expertise of some of the brightest minds in the field, including Nobel laureate Professor Shuji Nakamura, known for his groundbreaking work on blue LEDs, and his mentor, the visionary Professor Shiro Sakai.

Guided by Professor Sakai, Nitride Semiconductors focused on developing UV LEDs. In the fall of 2000, the company accomplished a major breakthrough by creating the world’s first 350 nm UV light-emitting diode. The partnership was also crucial as a strategic step in building the essential framework for Nitride Semiconductors’ ambitious journey into UV-LED innovation.

Over the past 24 years, Nitride Semiconductors has persevered and thrived in the UV-LED market. Today, it offers a full range of UV-LED solutions, from chips and packaged products to UV floodlights and UV irradiators. It has also launched its own brand, LEDPURE, offering deep UV-LEDs for home appliances like air purifiers, sterilizers and mosquito repellents.

An Innovative Leap in UV-LED Development

During the early 2000s, UV-LEDs were often viewed with skepticism. Emitting light in the range of 365 to 405 nm with an output of just 1 to 10 mW, these early models paled in comparison to the much more robust, conventional UV lamps. The majority of industry experts dismissed them as too feeble for practical applications. However, Nitride Semiconductors saw potential where others saw limitations. It focused on sensor applications that utilized fluorescent reactions, such as bill identification, capitalizing on the compact size, low energy consumption, and high reliability of UV-LEDs. This foresight allowed it to carve out a profitable niche in a market overlooked by larger LED manufacturers.

For Nitride Semiconductors, achieving such expansive growth and innovation, however, was not without its challenges. The journey to developing these advanced UV-LED products was fraught with technical hurdles, distinct from those faced in blue LED technology. A major hurdle was the high incidence of crystal defects in AlInGaN, the material used for UV-LEDs, which had significantly more imperfections than the InGaN used in blue LEDs. To combat this, Nitride Semiconductors developed sophisticated techniques to improve crystal quality, which were crucial for the success of its UV-LED products.

Adjusting material composition presented another complex challenge. Unlike blue LEDs, where variations in indium composition could enhance light efficiency, UV-LEDs required a reduction in indium to function effectively. The breakthrough came when the team adapted the use of gallium to replicate the beneficial effects seen with indium in blue LEDs and boosted the efficiency of UV-LEDs.

Another significant advancement came while addressing the issue of light absorption. The sapphire substrates traditionally used in the growth of LEDs absorbed light at 365 nm, substantially reducing device efficiency.

Nitride Semiconductors responded by developing a patterned sapphire substrate that minimized light refraction and absorption. In a bid to push performance boundaries, it also adopted a laser-based approach for GaN layer removal, cutting down on light absorption and boosting UV-LED efficiency.

Redefining Industrial Eco-Friendliness

The advantages of Nitride Semiconductors’ UV LEDs extend beyond their immediate applications, making a notable impact on global environmental and sustainability efforts. Traditionally, UV light has been essential in the production of silicon and compound semiconductors, as well as in liquid crystal and organic electroluminescence flat panel displays. But the prevalent use of mercury lamps for these processes poses considerable environmental risks. A hazardous substance, mercury endangers human health and disrupts ecosystems. Despite the known dangers, mercury lamps continue to be employed due to their widespread use in manufacturing processes.

The transition to UV LEDs marks a significant environmental milestone. By replacing mercury lamps with UV-LEDs, industries can significantly reduce their environmental footprint. Compared to traditional mercury lamps, UV-LEDs deliver several advantages, including better energy efficiency, longer operational life, and lower power consumption. Moreover, the shift to UV-LEDs supports sustainability by mitigating the adverse effects of mercury, contributing to a cleaner and safer environment.

In addition to their environmental benefits, the UV LEDs are designed with advanced technologies to ensure their efficiency and reliability across various applications. For instance, the company has made substantial improvements by replacing traditional sapphire substrates, known for their low thermal conductivity, with more effective materials such as copper tungsten. This enhancement has led to increased luminous efficiency and intensity. The company’s highest output UV-LED products achieve a light output of 4 watts with a wavelength of 365 nm and a luminous efficiency of 40 percent.

In the future, we anticipate that by applying the photonic crystal technology we are developing, we could significantly enhance the efficiency of UV-LEDs, potentially shifting the perspective of those reluctant to move away from traditional lamps

Nitride Semiconductors’ commitment to technological innovation is also evident in the mass production of micro UV-LEDs, which are crucial for micro-LED displays. These microchips, measuring just 50 μm square, are manufactured using robust AlInGaN-based materials, overcoming the fragility issues associated with materials like gallium arsenide and gallium phosphide used in red LEDs.

From Bill Validation to Space Safety

“In the future, we anticipate that by applying the photonic crystal technology we are developing, we could significantly enhance the efficiency of UV-LEDs, potentially shifting the perspective of those reluctant to move away from traditional lamps,” says Yoshihiko Muramoto, founder, president and CEO.

The applications of Nitride Semiconductors’ UV-LEDs are vast and varied, demonstrating their critical role across global industries.

The LEDs have become integral to bill validation systems worldwide. As essential tools for confirming the authenticity of currency and tickets, these systems rely on the LEDs’ precision and reliability. Despite cheaper alternatives flooding the market, the performance of Nitride’s UV-LEDs continues to garner trust, proving indispensable in safeguarding the integrity of financial transactions.

Apart from their application in currency validation, the company’s high-power UV-LEDs are instrumental in the curing process of UV-curable resins. These resins are used in a wide range of industrial and consumer applications, from coatings to adhesives. The UV-LEDs provide the necessary intensity and precision to effectively cure these resins, ensuring their optimal performance and durability.

Expanding beyond terrestrial uses, Nitride’s pioneering UVLED technology is reaching into the cosmos. It has been licensed to prominent entities such as Seoul Viosys in Korea and SETI in the United States. Notably, deep ultraviolet LEDs with a wavelength of 275 nm, incorporating this technology, are utilized on NASA’s International Space Station. These LEDs are vital for safeguarding the health and safety of astronauts during extended missions in space. Given the harsh conditions of space travel, where traditional UV lamps would be too fragile and energy-intensive, UV-LEDs offer a robust, energy-efficient alternative. Their durability and low energy consumption make them ideal for space environments, where reliability is paramount and energy resources are limited.

Illuminating Innovation

The narrative of semiconductor innovation has recently spotlighted Nitride Semiconductors for its groundbreaking work with ultraviolet light-emitting diodes (UV-LEDs). A milestone in this journey was reached with the publication of an influential paper in the August 2014 issue of Semiconductor, Science & Technology. Titled “Development and Future of Ultraviolet Light-Emitting Diodes: UV-LEDs Will Replace UV Lamps,” this paper marked a pivotal moment, reinforcing the company’s role as a pioneer in UV-LED technology.

Alongside this scholarly acknowledgment, the company has received prestigious accolades such as the 25th Semiconductor of the Year award. The honor, presented by the Semiconductor Device Division, recognized the company’s outstanding contributions to the semiconductor industry. The company was also honored with the Excellence Award from Sangyo Times Inc., further underscoring its leadership and innovation in the field.

Moving forward, the company is poised to continue its leadership in semiconductor technology with promising advancements in μLED displays. It is currently developing a cutting-edge μLED display system that utilizes micro UV LEDs to excite red, blue, and green phosphors. This innovative approach addresses the common challenges associated with conventional RGB μLEDs, such as the low luminous efficiency of red chips and the complexities of chip processing.

By adopting UV chips for phosphor excitation, Nitride Semiconductors has improved luminous efficiency and streamlined the production process. The application of photonic crystal nanoprocessing to the LED surfaces has further enhanced performance, setting the stage for breakthroughs in display technology.

Slated to begin mass production of these advanced displays by the latter half of 2025, Nitride Semiconductors is set to enhance its commitment to evolving UV-LED technology and aims to deliver versatile and high-performance solutions within the shifting display technology landscape.