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LumiLeds And UEC Settle AlInGaP LED Litigation And Consider Future Partnerships

LumiLeds Lighting, Agilent Technologies and United Epitaxy Company (UEC) have settled their pending litigation concerning US patent no. 5,008,718, which is now owned by LumiLeds (see Compound Semiconductor Sept/Oct 2000, p19).

Although the exact terms of the settlement were not disclosed, the parties have agreed to dismiss all claims and counterclaims asserted against each other.

In a separate but related agreement, LumiLeds has granted UEC a license relating to several patents, under which UEC will pay a license fee and royalties in undisclosed amounts. The performance of AlInGaP LEDs in the 560-680 nm range is compromised by poor current spreading and other problems. In 1989 Hewlett-Packard (HP) obtained a patent on a solution to the problem based on the use of a thick (230 micron) GaP layer grown on top of the active device.

The GaP layer acts as a "window" because it has a higher bandgap compared with AlInGaP and is therefore transparent to light emitted from the LED. The p-type GaP layer is also highly conducting, and therefore reduces the "current crowding" around the top electrode, resulting in more uniform light distribution.

Hewlett-Packard claimed that the GaP layer increased the light output by as much as five to ten times. The patent was transferred to Agilent as part of the spin-off from HP, and was subsequently transferred to LumiLeds (see ). After HP had alleged out of court that UEC was infringing on its patent, UEC responded in September 1999 with a lawsuit claiming that the patent was invalid (see Compound Semiconductor Dec 2000/Jan 2001, p13).

In July 2000, Agilent and LumiLeds filed a counter-claim that UEC was indeed guilty of infringement. The case was scheduled to go to trial later this year.

Sources close to the case said that UEC was defending itself against the infringement charges on the grounds that it was using InGaP rather than GaP in its window layers. They also argued that the patent was invalid because of "obviousness".

It is believed that LumiLeds riposte was that the use of such a strongly lattice-mismatched material was highly "non-obvious". There is a >3% mismatch between GaP and GaAs; ordinarily this would generate enough defects to kill a device like an LED. However, HP was able to make it all work because of the thickness of the window layer and its distance from the active layer. Both LumiLeds and UEC expressed pleasure that the dispute has now been resolved, and spoke about the possibility of working together beyond the license arrangements that have been agreed.

"We are pleased to reach an agreement in resolving the pending litigation," said Kuo-Hsin Huang, UEC s chairman of the board. "We re also happy that as part of the settlement, LumiLeds has agreed to consider partnering with UEC as a contract manufacturer for certain LumiLeds products." "We are pleased that UEC recognizes the value of our intellectual property," said Mike Holt, CEO of LumiLeds. "If LumiLeds wants to outsource absorbing substrate AlInGaP production in the future, we would consider using UEC as a supplier."

LumiLeds highest brightness AlInGaP products are transparent substrate LEDs, in which the absorbing GaAs substrate is removed and replaced by GaP using wafer bonding. To date, UEC has manufactured absorbing substrate LEDs but recently announced a fourth-generation design incorporating indirect wafer bonding to a transparent substrate such as glass or sapphire (see Compound Semiconductor September 2001, p51). "UEC will benefit in the expanding LED market from this patent license and a possible business partnership," concluded Kuo-Hsin Huang. "We think this is a win-win settlement for both parties."

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