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Report hints SemiLEDs-Seoul tie-up still on

Copper-substrate LED chips are still in use in the Z-Power LED P9 Series, says a teardown report by MuAnalysis.

A recent analysis has suggested that Seoul Semiconductor s P9 LED still uses die from SemiLEDs, even after their partnership saw both companies sued by Nichia.

A teardown from Canadian chip characterization laboratory MuAnalysis published March 17 found a GaN chip used in Seoul s Z-Power LED P9 Series possesses SemiLEDs trademark flexible copper substrate.

“Since I do not have a SemiLEDs wafer in my hand, I cannot be absolutely, absolutely sure,” conceded MuAnalysis CEO, Martine Simard-Nomandin, “but it is definitely on copper and it would be flexible.”

Now that plaintiff Nichia has settled long-standing patent cases with both SemiLEDs and Seoul Semiconductor the partnership should be able to continue without concern.

However, when the case was first filed Seoul s position was that most of the die for its P9 came from Cree, which already held a license from Nichia, and not SemiLEDs.

Simard-Normandin said that electron microscopy of the chip showed characteristics indicating that SemiLEDs approach of removing a sapphire substrate before replacing it with copper was used.

MuAnalysis has employed a “delineation etch“ in teardowns of LEDs from six different manufacturers to make their dislocations and quantum wells visible by microscope.

“We can recognize GaN grown on SiC, versus GaN grown on sapphire from the dislocations,” she explained.

On LEDs from Cree, which uses SiC substrates, Simard-Normandin says essentially no dislocations are visible, and the dice in Seoul s device initially appears similar.

“The P9 is very good, there are very few dislocations,” said Simard-Normandin. “It is among the best, but is not as good as Cree.”

“From the dislocations, it looks like it's done on sapphire and the sapphire has now been removed.”

She suspects that, in the P9, the flexibility of SemiLEDs copper substrate is a hindrance as the chip is paired with a stiffening construction to ensure it remains rigid.

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