Emerging applications for UV LEDs drive broad interest (MAGAZINE)
Martin Shih reports that while technology barriers remain in manufacturing UV LEDs, especially at shorter wavelengths, a number of potential high-volume applications are driving interest among packaged LED manufacturers.
While visible-spectrum LEDs have penetrated into TV and mobile backlighting, automotive, general lighting, signage, and other markets, ultraviolet (UV) LEDs are just beginning to replace incumbent UV sources in diverse applications, including curing, counterfeit detection, medical, sensing, printing, and water/air disinfection. The cost of UV LEDs has dropped significantly during the past several years through improvements in architectures and manufacturing technologies. However, when compared to the price of white LEDs, UV prices are still much higher and fewer manufacturers supply UV LEDs - although volumes are high for these suppliers. As a result, more and more white-light LED manufacturers are attempting to enter this field.
UV LED production
Strategies Unlimited has just released its new market research report, "The World Market for UV LEDs and Modules: Market Review and Forecast 2015." This report looks at packaged UV LEDs and modules using LEDs with wavelengths ranging from 100 nm to 400 nm. Unlike visible-light LEDs, UV LEDs that have wavelengths less than 350 nm are not grown on gallium nitride (GaN) substrates but rather are usually produced on aluminum nitride (AlN) substrates. UV LEDs can be divided into UV-A, UV-B, and UV-C spectral bands. The UV-A spectrum ranges from 315-400 nm; UV-B ranges approximately from 280-315 nm; and UV-C ranges approximately from 100-280 nm (Fig. 1).
FIG. 1. UV LEDs cover a broad radiometric spectral band and are general broken into UV-A, UV-B, and UV-C segments.
For the production of UV LEDs, lower wavelengths generally equate to the need for more aluminum content in the epitaxial (epi) layers grown on the substrate. The standard metal-organic chemical vapor deposition (MOCVD) tools used for epi growth in visible LEDs can be used to produce UV-A LEDs. But UV-B and UV-C LEDs require specialized tools for production, which greatly raises barriers for entry when compared to their UV-A counterpart. This latest report covers all wavelengths and analyzes the current market landscape of all UV LEDs, projecting how the market will grow over the next five years.
Forces behind different types of UV LEDs
A few years ago, it was almost unheard of for visible-spectrum packaged LED manufacturers to consider the UV market. There was more money to be made in visible LEDs and the barrier to entry in UV was high. But the UV market was ripe for this LED alternative.
Most applications where UV light is needed have relied on traditional mercury-vapor sources, which require time to warm up, can easily create ozone, and use toxic materials to create the light. As the industry is becoming more widely aware of these concerns, UV LEDs appear to be perfect replacements: They start up immediately, will save energy as they do not have to be kept on, don't contain toxic materials like mercury, and have greater design flexibility. All of these factors make UV LED luminaires better suited for the current market.
That being said, the replacement of traditional UV lamps with UV LED technologies is only the tip of the iceberg with regard to the potential for the UV LED market. New applications where UV could be used include UV-A integration in smartphone/handheld devices for counterfeit detection or analysis, and UV-C integration in refrigerators or other medical devices for disinfection. Fig. 2 illustrates more application examples across the bands.
FIG. 2. There are established applications for UV light across the UV bands, but LEDs will also enable new high-potential applications.
The highest penetration and usage of UV LEDs today is in curing applications, but other applications such as water and air disinfection are increasing their reliance on UV LEDs as the technology evolves. This growth is expected to continue in the next five years and new potential applications will emerge.
The largest growth opportunities, however, will stem from new applications such as the aforementioned UV-A integration into everyday items like smartphones/handheld devices for counterfeit detection or analysis. Likewise, UV-C integration into refrigerators for disinfection has huge potential. Still, these new applications are in the very early stages of R&D, so it is difficult to forecast these markets.
Global market for UV LED applications
Now let's consider the market potential. Fig. 3 projects the revenue breakdown by type of UV LED: UV-A, UV-B, and UV-C. In general, UV-A LEDs have higher penetration rates among all applications because of lower prices. UV-A is a very good entry point for these packaged LED manufacturers that produce white-light LEDs since they can use their current MOCVD tools. It is forecasted that the market for UV-A packaged LEDs will grow by approximately a 45% compound annual growth rate (CAGR) over five years through 2020.
FIG. 3. Global UV LED package revenue is broken down by type (spectral band).
Fig. 4 projects the global potential for UV LED package by applications. As previously mentioned, the curing industry has had the greatest usage and penetration of UV LEDs. That being said, other applications are beginning to increase their usage of UV LEDs as the technology evolves, with printing being the other main category in the UV-A market. In general, a large printer needs a UV light engine with approximately three to four rows of LEDs comprising hundreds of 1W UV LED die.
Although water/air disinfection has a lower penetration rate compared to other applications, we still forecast that the market has great potential and this is the main driver for UV-C LEDs. From our research, we found the major market regions to be in North America and Japan. Although the usage of UV LEDs is relatively limited in countries such as China and other emerging global markets, it is expected that these regions are poised to undergo
significant growth in the next five years as well.
FIG. 4. The UV LED package revenue forecast by applications from 2014-2020 shows that UV LEDs for the printing application are expected to increase considerably.
FIG. 5. The UV LED module revenue forecast by applications from 2014-2020 anticipates growth in UV LEDs for disinfection.
Fig. 5 projects the global market for UV-B and UV-C modules by application. UV-B and UV-C LEDs are usually sold as modules because their manufacturers want to have more quality control over their products, as well as more control over their intellectual property (IP). As water/air disinfection, sensing, and medical markets expand, the market for UV-B/UV-C modules is expected to experience tremendous growth as well, with a forecasted 49% CAGR from 2014 through 2020.
Suppliers and obstacles
As mentioned before, both UV-B and UV-C need specialized manufacturing tools, and as a result, the entry barrier in those bands can be higher. In terms of LED chip manufacturing, epi layers of InGaN (indium gallium nitride) and GaN, grown by MOCVD, are used for most UV-A LEDs. With the shorter wavelengths of UV-B and UV-C LEDs, the processes require the use of AlGaN (aluminum gallium nitride) for the added aluminum required.
It is easier to grow AlGaN-based materials on AlN substrates rather than sapphire. However, AlN substrates are only available in small sizes and that fact plays a part in the LEDs being much more expensive.
Indeed, the manufacturing obstacles described will produce more of a barrier to the UV-C band when it comes to some makers of visible-light LEDs. We expect big LED players to merge with or acquire UV-C manufacturers in order to obtain the technology in a short time.
Still, according to our global top 10 packaged-LED manufacturers in the "Worldwide Market for LEDs: Market Review and Forecast," 4 of the top 5 UV LED suppliers in 2015 are visible-LED makers. It is interesting that Cree has almost no established presence in UV LEDs in 2015. But we have heard rumors from Cree peers discussing their UV LEDs. For other major packaged-LED makers dabbling in UV LEDs, the UV products typically account for less than 1% of total revenue.
As the demand for UV-B and UV-C products increases and their prices decrease, we expect to see more competition and product options. This enthusiasm will further expand the market for these goods, as is the case with UV-A LEDs.
MARTIN SHIH is responsible for LED supply chain and market trends in Taiwan/China for Strategies Unlimited (strategies-u.com). He has more than a decade of experience in the electronics industry, mainly covering semiconductor and hardware technology.