Light against Viruses – 1:0

An OSRAM develop­ment team has created light that does not actually exist on Earth, and is using this UV-C light to disin­fect surfaces, air and water. The recipe: Take an LED and add some highly special­ized know-how and the courage to think outside the box.

What if you could disin­fect the air in a room simply by swit­ching the lights on for ten minutes? Or place a cell phone in a box for a few minutes to kill all the germs on it? It may sound futu­ristic but it’s already reality. This is dis­infection with short-wave ultra­violet radia­tion – UV-C light.

UV-C radia­tion doesn’t actually exist natu­rally on Earth. It is absorbed by the ozone layer before it can reach us. Which is a good thing because short-wave light has such high energy that it can break the chemical bonds in an RNA or DNA helix. Genetic infor­ma­tion is destroyed as a result. This has the posi­tive effect that viruses or bacteria cannot multiply and will no longer be infec­tious. So UV-C light is a highly promi­sing tool for successful disin­fec­tion.

But this radia­tion not only destroys the cells of viruses and bacteria, it can cause serious damage to our skin or eyes. Contact with UV-C light is dange­rous, so protec­tive clot­hing is essen­tial.

Systems that use light to purify the air are curr­ently equipped with conven­tional gas discharge lamps as the light source. They do, however, have a crucial disad­van­tage in that mercury can leak out if they break, making them unsui­table for mobile appli­ca­tions except in certain specific circum­s­tances. Unlike the light emit­ting diode, or LED for short. The LED is small, versa­tile, durable and vibra­tion-resistant – and it can emit UV-C light. A germ killer you can take anywhere is there­fore tanta­li­zingly within reach. The chal­lenge right now can be summed up in one word: effi­ci­ency. At just four percent, the UV-C LED still has plenty of room for impro­ve­ment here. And that is precisely the focus of the OSRAM team.

Deve­lo­pers at OSRAM are working on a breakthrough. A task that requires crea­ti­vity, perse­ver­ance and an accep­t­ance that there will be setbacks. And a parti­cu­larly exci­ting task for the team.

Who is behind the tech­no­logy?

High-tech needs people. And these people need high-tech. See for yourself who the crea­tive minds are behind the tech­no­logy of the UV-C-LED.

Hans-Jürgen Lugauer:

makes semi­con­duc­tors emit light

Lugauer is a physi­cist and Senior Manager in Prede­ve­lo­p­ment at Osram Opto Semi­con­duc­tors

Hans-Jürgen Lugauer is used to setbacks. “If you can’t deal with setbacks then prede­ve­lo­p­ment is not the place for you”, he says. Lugauer knows what he is talking about. After all, he has been working at Osram since 1999. It was his first and only job appli­ca­tion after comple­ting his docto­rate at the Univer­sity of Würz­burg, and for Lugauer to this day it’s a perfect match.

“I love this job. It’s great fun and suits me just fine. Obviously, there are times when things don’t go so well and after inves­ting lots of time and effort I have to start all over again. I have to be able to deal with that.” But he couldn’t imagine it any other way: „I don’t want to do anything if I don’t know why I’m doing it. A routine job would not be for me – I need a certain chal­lenge.” After working on the deve­lo­p­ment of LEDs for the visible spec­trum, his chal­lenge now is to develop LEDs that emit UV-C light.

The fun of cracking a hard nut

Lugauer’s tasks have changed over time. He is now to be found more at his desk than at a labo­ra­tory bench. Does he miss the hands-on approach? “Yes, I really miss that. I keep getting the itch to do some­thing actively myself. But I try to stay as close to the tech­no­logy as possible so that I can still under­stand problems in great detail. A manage­ment job pure and simple without a tech­nical connec­tion would not be for me,” he added.

“I try to stay as close to the tech­no­logy as possible so that I can under­stand problems in detail.”

Whenever it gets really tricky, he likes to take a little time-out alone to get to grips with what it’s all about – and then discuss his thin­king with the team. Without this inter­ac­tion with his colleagues he would not be able to move forward. It’s one of the most important elements of his work.

He likes the crea­tive colla­bo­ra­tion that is possible and indeed essen­tial in prede­ve­lo­p­ment. “I’m crea­tive, and that goes hand in hand with being a little unst­ruc­tured. I’m working hard to keep this within limits,” he admits with a laugh.

Lugauer laughs a lot – even at work: “It’s important to me that we retain a sense of humor. We laugh a lot, even at normal ever­yday things. It’s some­thing that moti­vates me and my colleagues. If I didn’t have fun, I wouldn’t be happy.”

Light with social rele­vance

Toge­ther with this moti­vated team, he now creates light that renders viruses harm­less. That gives his work another special meaning, as he explains: “It feels good that small, mobile devices with UV-C light will soon be able to disin­fect the air in a room, for example in hospital wards, so that fewer people die from bacte­rial and viral infec­tions. We are deve­lo­ping some­thing really rele­vant for society here. With our UV-C-LED we can replace the mercury lamps that have been used so far. That would be a huge leap forward for the health of the popu­la­tion and for the envi­ron­ment. That gives me a really good feeling.”

The Basis: 

the semi­con­ductor crystal

Alumi­nium gallium nitride (AlGaN) is the basis for UV-C light. This semi­con­ductor crystal is a compound of aluminum, gallium and nitrogen. This means that UV-C-LEDs are funda­ment­ally diffe­rent from blue LEDs, on which the commer­cially avail­able white LEDs are based. The compound for blue LEDs is indium gallium nitride (InGaN). To achieve UV-C light the deve­lo­pers replaced the indium with aluminum. Sounds simple but it’s not, because the two compounds have diffe­rent mate­rial proper­ties. Which means that AlGaN behaves comple­tely differ­ently from InGaN. As a result, new deve­lo­p­ment and manu­fac­tu­ring processes are also needed.

Shine on you crazy crystal

The big chal­lenge is to make the mate­rial emit light. That’s not some­thing it does by itself. The AlGaN semi­con­ductor is a very good insu­lator even at room tempe­ra­ture. This essen­ti­ally non-conduc­ting mate­rial only becomes a conduc­ting mate­rial through the selec­tive addi­tion of atoms. This process is called epitaxy. In the chemical depo­si­tion process, the raw mate­rials are trans­ferred to a reactor in gaseous form where they react with each other under extre­mely high tempe­ra­tures of well over 1,100 degrees Celsius on a suitable layer known as a substrate.

The conven­tional silicon used in the semi­con­ductor world is unsui­table as a substrate because the grid spacings of the two crys­tals differ too much and UV-C radia­tion is absorbed. In most cases, aluminum oxide (Al2O3), also known as sapphire, is there­fore used for blue, green and white LEDs based on InGaN. Sapphire is also the substrate of choice for produ­cing UV-C light in the case of aluminum gallium nitride because its physical proper­ties match very well with those of the semi­con­ductor. It is also trans­pa­rent for UV-C radia­tion.

Wafer thin

The epita­xial process itself is largely the same as in the produc­tion of conven­tional LEDs. Well over one hundred wafer-thin layers are depo­sited one on top of the other. The most important ones, the so-called “quantum wells”, are thinner than ten atomic layers. However, a lot of theo­re­tical work is needed to ensure that the LED emits the short-wave UV-C light at the correct wavelength of 260 to 280 nano­me­ters. The layer struc­ture is complex, and the inter­ac­tions between the layers are also complex. How exactly they interact with each other is only known when the chip is ready, but their thic­kness and compo­si­tion are deter­mined in advance on a theo­re­tical basis in order to obtain the best possible result.

Finally, ever­ything comes toge­ther. The first step is to create a buffer layer, then the active LED layers and finally a contact layer is applied. At this point, rela­tively fine adjus­t­ments can be made to the wavelength of the light. The key is the ratio of aluminum and gallium in the active LED layers.

Trou­ble­shoo­ting with an atomic force micro­scope

Ques­tions and fresh chal­lenges arise again and again during the fabri­ca­tion process. Here’s a good example: As soon as the LED struc­ture is built up layer by layer as far as the contact layer it already emits some light, but not enough. The search for a means of adjus­t­ment begins. Is the selected struc­ture the best one? Where are the compo­si­tions wrong? Where do struc­tures need to be removed or added to make impro­ve­ments? Where are elec­trons being lost?

To search for the fault an atomic force micro­scope may be used to minu­tely scan the surface of the buffer layers and make the atomic struc­tures visible. Are they smooth or rough? Are there holes or defects caused by parti­cles?

X-rays also show how the layers are composed and where the tensions between them lie. The LED layers are tested for their conduc­ti­vity. Depen­ding on how well the layers conduct, the deve­lo­pers can tell whether they are on the right track or whether they need to rethink the layers and their compo­si­tion. Again and again, this means taking one or more steps back or even star­ting again from scratch and rethin­king ever­ything.

Chips no bigger than a grain of sand

This also applies to the next step – chip proces­sing. The wafer produced in the epitaxy process is struc­tured, provided with metal contacts and then divided into small cubes, the chips. The tiny crys­tals, no bigger than a grain of sand, must be cut out of these wafer. They are the ones that will later emit UV-C light.

As things stand today, however, they do not yet do this effi­ci­ently enough. Whereas blue LEDs can achieve an effi­ci­ency of well over 60 percent, UV-C-LEDs curr­ently only manage about four percent. For deve­lo­pers, this is still the hardest nut to crack.

Alex­ander Wilm:

is buil­ding a house for the LED

Wilm is a graduate in mecha­tro­nics and Senior Key Expert Appli­ca­tions at Osram Semi­con­duc­tors

Alex­ander Wilm needs a chal­lenge. He feels most comfor­table in unknown terri­tory: “I like to work on topics that are new to me and help shape future tech­no­lo­gies. And as soon as ever­yone else is doing the same thing, I go looking for some­thing new again,” he says with a smile. Fortu­n­a­tely, there has always been plenty to keep him occu­pied at Osram in the last 16 years. The LED has accom­pa­nied him throughout, or rather he has accom­pa­nied the LED – in car head­lamps, cell phones, projec­tors, green­houses and street lamps. Inclu­ding a two-year stint in Sing­a­pore.

He says he has there­fore never had a reason to move to a diffe­rent employer. Instead, there has always been much to discover and bring to frui­tion. Like now with the UV-C-LED for disin­fec­tion. In Appli­ca­tion Engi­nee­ring, Wilm is the inter­face between deve­lo­p­ment and the custo­mers. In other words, he discusses concepts and proto­types with a customer and takes the customer’s wishes and requi­re­ments back to his colleagues to then work out with them whether they are feasible.

Just spin­ning around

He likes the mix: “For me, the working envi­ron­ment here is incredibly good and crea­tive. I need an envi­ron­ment in which I can think freely and that’s what I’ve got here. Anyone who wants to develop high-tech solu­tions needs the space to freely spin things around and around.” That’s precisely what he can do so in special crea­ti­vity work­shops. “The aim is to escape from evolu­tio­nary deve­lo­p­ment and create some­thing comple­tely new. Take a comple­tely diffe­rent approach.”

“We have to escape from evolu­tio­nary deve­lo­p­ment and create some­thing comple­tely new. Take a comple­tely diffe­rent approach.”

You should not be afraid to make mistakes, and you should have the courage to engage in a free and frank dialog: “I’m a fan of talking through problems. If some­thing isn’t working you have to say so without hesi­ta­tion. At the end of the day, we can learn a lot from that.”

Taming light

The evening is Wilm’s favo­rite time for tack­ling tricky problems: “Whenever I need to get to grips with a topic, I usually find a quiet time in the evening away from work,” he says. Some­times he thinks about the respon­si­bi­lity of deve­lo­ping the UV-C-LED. “The tech­no­logy is not exactly harm­less. The LED needs to be used respon­sibly. Control mecha­nisms and sensor systems will help us. Even here there are plenty of possi­bi­li­ties and plenty of work to do,” says Wilm.

He is convinced that the LED will keep him busy in this and other appli­ca­tions for a while. “I believe that we are only just star­ting to appre­ciate what the LED as a light source can do, as it is so versa­tile and universal. There are so many new ideas and concepts to explore. It would be fun for me to journey into more of this uncharted terri­tory.”

Well protected:

the package


A chip by itself is extre­mely deli­cate. It needs protec­tion, and that protec­tion is known as a package. The package has a number of func­tions. It provides the electrical connec­tion to deliver power to the LED. It also ensures that a place­ment machine can pick up the LED and place it on a pcb without dama­ging it. At the same time, it performs optical func­tions. With a small reflector in the package, it is possible to direct the light or radia­tion.

Hot stuff

Thermal manage­ment plays an important role in the design of the package. Because the hotter an LED gets, the faster it ages. Only four percent of the electrical energy that is fed into the LED is emitted as UV-C radia­tion, the rest is power loss – and that gene­rates heat. This means that the package has to remove as much heat from the chip as possible. The better it can do this, the cooler the chip stays and the longer it will last. This is a critical point for the deve­lo­p­ment process because a larger package, for example, will lead to better heat dissi­pa­tion, but larger often means more expen­sive.

Deve­lo­pers simu­late whether and how well thermal manage­ment will work before they build proto­types. They begin this process with very broad brush­strokes, explo­ring diffe­rent concepts. Finite element methods help them to assess the effects of mate­rial inter­ac­tions. The 3D element to be computed is broken down into smaller elements which are then analyzed for their physical beha­vior. This is important because the indi­vi­dual mate­rials that make up the package have diffe­rent coef­fi­ci­ents of expan­sion. This leads to internal tensions as the tempe­ra­ture rises. Simu­la­tions can deter­mine whether the connec­tion points will with­stand these tensions so that design solu­tions can be found if necessary. Small features such as angled or rounded edges often influ­ence how well tensions can be miti­gated.

Shaping the light

Depen­ding on the appli­ca­tion in which the UV-C light is to be later used for disin­fec­tion, the emis­sion charac­te­ris­tics also have to be tailored. Among other things, the emitted light can either be fanned out widely or bundled tightly. If, for example, water or air passing over the LED is to be puri­fied, it is advi­s­able not to closely cluster the radia­tion source but to distri­bute it along a water or venti­la­tion pipe so that the medium is uniformly irra­diated. In contrast, disin­fec­tion of water at a faucet or objects in small portable boxes requires signi­fi­cantly smaller and concen­trated flows of radia­tion. This can be achieved through the design of the package.

Rethin­king is also the order of the day when it comes to selec­ting the mate­rials for the package. Simply adop­ting the mate­rials used for conven­tional LEDs will not work because the plastics and organic encap­su­la­tion mate­rials used for those LEDs would decom­pose due to the high-energy radia­tion of the UV-C light. So deve­lo­pers look for mate­rials that will produce a stable, solid and durable package. Cera­mics, glass and meta­lized foils have proved their worth to date.

Test to failure

If a package variant seems promi­sing in the simu­la­tion it will be built as a proto­type and must survive dest­ruc­tive testing. In this test, the package is subjected to incre­a­sing loads until it fails. It is exposed to signi­fi­cantly more sever opera­ting condi­tions and loads than would occur in the real envi­ron­ment. Endu­rance tests reveal whether joints are dete­rio­ra­ting and how the mate­rial is aging. This in turn allows conclu­sions to be drawn about the life of the LED.

Once all the requi­re­ments have been defined and the package has been desi­gned, the produc­tion depart­ment will check whether the package can be produced in large quan­ti­ties. If so, that signals the end of the deve­lo­p­ment project and the start of series produc­tion.

André Köhler:

swit­ches on UV-C light

Köhler is Global Product Manager Airfield, Medical, UV at OSRAM DI Industry

André Köhler wanted to study at the Film and Tele­vi­sion College in Babels­berg because he had always been fasci­na­tion by the cinema and movie produc­tion. Instead, he studied econo­mics, socio­logy and psycho­logy. But he never lost his fasci­na­tion for what light could do.

When OSRAM relo­cated its specialty lamp busi­ness to Berlin in 2000, Köhler said to himself: “I think I’ll apply there.” A short time later he started in sales, became a product manager and was then closer to his passion for film and tele­vi­sion: “Our products opened the doors to movie sets and cinemas. I enjoy the customer envi­ron­ment and the appli­ca­tions. I could never have seen myself in general ligh­ting, but special lamps and contact with end custo­mers are exci­ting.”

Complete device instead of a compo­nent

Special lamps also include those that emit UV-C radia­tion. They have been at the top of Köhler’s task list for over two years. “The market is crying out for this means of disin­fec­tion. Many new compa­nies are now working on the tech­no­logy, but need help with inte­gra­ting the lamps. As a result, we suddenly find ourselves in the role of equip­ment manu­fac­turer and are more involved as consul­tants,” says Köhler.

“The market is crying out for UV-C as a means of disin­fec­tion.”

The time pres­sure is enor­mous because unless you’re quick you’ll miss the market.” This is why lots of things run in parallel. That’s parti­cu­larly true for him as he coor­di­nates ever­yone involved in deve­lo­p­ment, produc­tion and logistics. “I am basi­cally a person who needs calm­ness and struc­ture, but in stressful situa­tions I adapt,” he adds. “In the past, OSRAM was the super­tanker gliding across the sea. Changes came slowly but always after much consi­de­ra­tion. Things are diffe­rent now. Markets are chan­ging rapidly and compe­ti­tion is fierce. Now we need to react quickly to new circum­s­tances. “We can no longer take two years to develop a UV-C device and then launch it on the market. Those days are long gone. We have to adapt the processes and often take a fairly prag­matic approach.”

His team is curr­ently working on a UV-C product port­folio – for a whole new target group. “Up to now, our custo­mers have been profes­sional users, but now we are selling to private custo­mers. That means we need to use enti­rely diffe­rent sales chan­nels and sell via online plat­forms such as Amazon. This is still new terri­tory for us.”

Don’t panic!

There is also a need to rethink the safety features for devices with UV-C light. They have to be desi­gned so that even private users can use them safely. Köhler believes that is both a chal­lenge and a great oppor­tu­nity: “We no longer only supply the source of radia­tion, but also offer complete solu­tions inclu­ding sensors.”

For Köhler, close coor­di­na­tion with his colleagues is an essen­tial element along the path to a new product. Espe­cially when things get tricky. His approach is to let things sink in for a while, avoid pani­cking and work out with the team what a solu­tion might look like. “It’s important for me to keep moti­vating people,“ says Köhler. “I’m basi­cally a posi­tive person – my glass is always half full. Every setback is an expe­ri­ence and can be over­come. As the leader, I try to convey this to my team. The really important ingre­dient is humor. Humor always helps me to pull myself out of diffi­cult situa­tions.”

In use: 

UV-C-products

Products with conven­tional lamps as sources of UV-C are already avail­able. OSRAM’s AirZing is one of them. First deve­loped for the Chinese market, the device was initi­ally used in early 2020 to disin­fect the air in the hospi­tals set up in Wuhan during the intense phase of the corona pandemic. AirZing is now being used throughout the world. If there are no people in a room, the device is swit­ched on and cleans the air and surfaces with its UV-C radia­tion. As soon as someone enters the room, sensors detect this move­ment and immedia­tely turn off the light to prevent damage to skin and eyes.

The issue of effi­ci­ency

But these devices are still equipped with conven­tional discharge lamps that produce UV-C light. The effi­ci­ency of the LEDs is not yet good enough to flood large rooms with UV-C light. For a conven­tional lamp with 30 W of electrical power, effi­ci­ency is between 30 and 40 percent, which equates to about twelve watts of UV-C output. If you want to replace a 30 W lamp for disin­fec­ting a room, you would need a large number of LEDs. That would not make economic sense. Repla­cing a lamp with an LED is just not possible yet.

The LED is ideal, however, for use in mobile appli­ca­tions. It is compact, shatter-proof, vibra­tion-resistant and does not contain mercury. For deve­lo­pers that’s reason enough to create devices in which the LED does a good job even with low effi­ci­ency. A compact device for disin­fec­ting small areas is a promi­sing concept.

Small areas at the start

The idea here is for UV-C light to disin­fect the air in a room by means of perma­nent circu­la­tion. The used air is drawn into the device where it is steri­lized and then directed back into the room. To disin­fect a defined volume of space, a certain UV-C output is required and a certain velo­city at which the air is chan­n­eled past the UV-C source.

With a normal LED unit this is not possible due to the low effi­ci­ency and the high cost. The solu­tion: a HEPA filter (high-effi­ci­ency air filter) installed upstream of the UV-C LEDs to trap the viruses. This germ trap is then cleaned by a small UV-C LED unit. Instead of disin­fec­ting all the air, the UV-C light shines only on the filter and steri­lizes it. LEDs could there­fore soon be opera­ting in large areas.

Rese­arch is also being carried out on small devices, such as a UV-C LED box in which the light removes viruses and germs from the surfaces of cell phones and other objects. That would be a “germ killer to go”.

OSRAM Licht AG

OSRAM makes the world brighter. With around 21,000 employees world­wide, the Munich-based company is deve­lo­ping appli­ca­tions for the future in its three busi­ness units (Opto Semi­con­duc­tors, Auto­mo­tive and Digital). What does it need? An eye to the future, visible and invi­sible light and bril­liant employees. Its lamps and LEDs illu­mi­nate so many diffe­rent things inclu­ding green­houses, cars, cinemas, runways, streets and even cycling clothes. And they make viruses harm­less with UV-C light.


Foto­grafie: Jan Hosan