ZnO LEDs market analysis A
s a material for making LEDs, ZnO has loads to recommend it. It is cheap, non-toxic, and
chemically stable; it is incredibly well understood; it can emit light very efficiently; and it is capable of making devices that span the ultraviolet to the infrared. However, despite all its promise, the ZnO LED has failed to make any commercial impact. That is partly because material issues have hampered device development — realizing p-type doping in this material has been a major challenge, and there have also been differences of opinion over the design of the active region needed to yield a light-emitting device.
While these issues have undoubtedly hampered the progress of the ZnO LED, they are not the primary reason why this device is still confined to the lab, according to Lawrence Gasman, Principal Analyst at the market research firm NanoMarkets. He believes that if a large firm had financed a major effort at commercializing ZnO LEDs, they could have ironed-out the technical issues in just a year or so.
“I see the obstacles as being on the business side,” says Gasman, who points out that winning venture capital investment for novel semiconductor businesses is far, far harder than it was before the credit crunch. However, that’s not to say that there is no funding for ZnO LED development. This device has ‘green’ credentials, and some start-ups have won funding on the back of that attribute.
Gasman expects the first ZnO LEDs to hit the market in two to four years time. “The LED market is slated to grow very fast now, and if ZnO can knock off a segment of that market in a time starting in three or fours years from now, then that [sub-section of the] market can be very substantial.” He believes that ZnO LEDs will make an impact and net $415 million in 2015. That will make this device the biggest earner for ZnO, which will also be used to build transistors and provide a transparent, conductive oxide for displays and photovoltaics (see box “The great versatility of ZnO”).
Starting with ultraviolet The pioneers of ZnO LED manufacture will begin by making ultraviolet emitters. This is the simplest form of the device to produce, because ZnO’s bandgap is 3.3 eV.
“The market for [ultraviolet lighting] is not huge, but it’s a good place to start, because you are not completely reliant on the whims of everyday consumers,” claims Gasman. Today lamps with fairly short lifetimes are the most common providers of ultraviolet emission, which is used for water purification and medical treatments. ZnO LEDs promise to be a far more reliable source.
Another reason why ZnO LED makers will target the
ultraviolet market first is that it will allow them to get their businesses off of the ground without having to compete with huge, well-established GaN chipmakers. “If you are in the UV business, you are talking about a much more modest supply chain [than the general illumination business], which a small firm could conquer with a couple of decent sales guys and a business development guy,” says Gasman.
Once the ZnO LED manufacturers have enjoyed some success in this market, they will add phosphors to their devices to produce white emitters. These promise to be cheaper than the GaN incumbents, which are starting to penetrate general lighting but need to drop in price to fuel the rapid adoption of this technology.
“The hope is that ZnO will give a range of colors that are more attractive than CFLs and GaN LEDs,” says Gasman. This could help to spur the sales of these ZnO emitters, because, according to Gasman, many people have the perception that GaN-based LEDs produce a cold and harsh form of white light. “The companies that are working on ZnO LEDs claim that you can get better color quality from these LEDs.”
According to Gasman, another strength of the ZnO LED is the abundance of its constituents: “There is plenty of nitrogen around, but maybe there is some constraint on gallium. Remember that there has been a dance between cost and supply of indium, for indium tin oxide.” Although incredibly small amounts of indium tin oxide are needed to make a display, billions and billions of screens are made every year.
One difficulty facing the pioneers of any innovative technology is the reluctance of potential customers who may be suspicious of adopting the new materials. However, this should not be a major issue for the ZnO pioneers. “Samsung has announced using carbon nanotubes for backlighting and displays, and they are actually producing that now,” says Gasman. He is also aware of companies working with silicon quantum dots, and he sees ZnO as just another emerging material in this sector.
According to Gasman, there might be up to a dozen companies working towards the commercialization of ZnO LEDs. They tend to keep a very, very low profile. “In some cases they are funded by famous names,” says Gasman.
The progress of all of these firms is held back by the materials and processing equipment. One issue is that there are only about ten producers of crystalline ZnO, and the substrate sizes produced by them are too small for mass production. For example, the material offered by the Atlanta-based firm Cermet is either shipped as 10 mm by 10 mm squares, or 25 mm-diameter circular substrates.
November / December 2010
www.compoundsemiconductor.net 15
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