Researchers demonstrate VCSELs grown on IQE material capable of maintaining high performance at elevated temperatures

25 January 2011

Cardiff, UK - 25 January 2011: A team of researchers from the Technical University of Berlin has published work in Applied Physics Journal demonstrating record data transmission rates from an oxide confined 980nm Vertical Cavity Surface Emitting Laser (VCSEL) operating at 85°C.
The VCSEL devices fabricated on wafers produced by IQE’s optoelectronic facility in Cardiff, UK, are capable of operating at 25Gbit/s at elevated temperatures, making them ideal for very short optical links within high-performance computers.
Since temperatures inside computers are as high as 85 °C, or even higher, good temperature stability is indispensable for robust, inexpensive optical links,” says Dieter Bimberg, head of the research team at the Technical University of Berlin.
Most short-reach optical links and local and storage-area networks currently operate at a wavelength of 850nm but Bimberg believes there is a strong case for 980 nm sources in all these applications.
980 nm has the crucial advantage of transparency of the GaAs substrate, so one can easily realize bottom-emitting devices, increasing and simplifying packaging density. This is very important, for example, in the case of a large number of VCSELs for parallel optical links.
The VCSEL wafers are produced by IQE’s Metal Organic Chemical Vapour Deposition (MOCVD) tools at its facility in Cardiff, UK. The epitaxial structure contained 24 pairs of Al0.12Ga0.88As and Al0.90Ga0.10As layers for the bottom mirror, and a further 37 pairs for the top mirror. Sandwiched between these mirrors is an active region with five compressively strained 4.2nm thick In0.21Ga0.79As quantum wells interlaced with 6nm thick GaAs0.88P0.12 tensile strained barriers.
Output from a 10μm-diameter oxide aperture VCSEL is 4.3mW at 20 °C and 2.6 mW at 85°C. This relatively small reduction in power stems from an intentional red-shift detuning of 15 nm between the quantum well gain peak and the cavity resonance. The devices have bit error rates at 25 Gbit/s of less than 10-12.
Future targets for the team are to speed the 980 nm VCSELs to 40Gbit/s and maintain this rate at 100°C.


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Note to Editors
ABOUT IQE (www.iqep.com) IQE is the leading global supplier of advanced semiconductor wafers with products that cover a diverse range of applications, supported by an innovative outsourced foundry services portfolio that allows the Group to provide a 'one stop shop' for the wafer needs of the world's leading semiconductor manufacturers.
IQE uses advanced crystal growth technology (epitaxy) to manufacture and supply bespoke semiconductor wafers ('epi-wafers') to the major chip manufacturing companies, who then use these wafers to make the chips which form the key components of virtually all high technology systems. IQE is unique in being able to supply wafers using all of the leading crystal growth technology platforms.
IQE's products are found in many leading-edge consumer, communication, computing and industrial applications, including a complete range of wafer products for the wireless industry, such as mobile handsets and wireless infrastructure, Wi-Fi, WiMAX, base stations, GPS, and satellite communications; optical communications, optical storage (CD, DVD), laser optical mouse, laser printers & photocopiers, thermal imagers, leading-edge medical products, barcode, ultra high brightness LEDs, a variety of advanced silicon based systems and high efficiency concentrator photovoltaic (CPV) solar cells.
The manufacturers of these chips are increasingly seeking to outsource wafer production to specialist foundries such as IQE in order to reduce overall wafer costs and accelerate time to market.
IQE also provides bespoke R&D services to deliver customised materials for specific applications and offers specialist technical staff to manufacture to specification either at its own facilities or on the customer's own sites. The Group is also able to leverage its global purchasing volumes to reduce the cost of raw materials. In this way IQE's outsourced services, provide compelling benefits in terms of flexibility and predictability of cost, thereby significantly reducing operating risk.
IQE comprises eight operating facilities located in Cardiff (two), Milton Keynes and Bath in the UK; in Bethlehem, Pennsylvania, Somerset, New Jersey and Spokane, Washington in the USA; and Singapore. The Group also has 11 sales offices located in major economic centres worldwide.