Sony Computer Entertainment Inc.'s much-anticipated Playstation 3 videogame console hit U.S. stores Friday, just days after initial shipments of the system in Japan sold out in a matter of hours. Though priced starting at $499 for the more basic of the two models, the PS3 is in many ways the signature consumer electronics product of the 2006 holiday season. Some consumers even camped out overnight to get their hands on one.
But the PS3 won't be a runaway hit this holiday season, for one reason: Set back by production problems for the blue-laser diodes used in the consoles' optical disk system, Sony cannot deliver enough of them.
Sony's initial shipments400,000 units in the States, and reportedly somewhat less than the 100,000-unit volume Sony had promised in Japanare less than half what the company had initially planned to deliver and not nearly enough to meet demand.
The shortfall has been blamed on problems in the production of blue-laser diodesmore precisely, blue-violet lasers with a 405-nanometer wavelength. Those problems have persisted through more than a decade of blue-laser development.
"It is really challenging to get a high yield in gallium nitride device production," said Shuji Nakamura, a professor of materials engineering at the University of California, Santa Barbara, who is best known as a pioneering developer of volume-manufacturing technology for GaN-based LEDs and lasers. "No one has succeeded in manufacturing GaN lasers in really large volumes," Nakamura said, so it's not surprising Sony's engineers "have had a hard time."
The biggest problem, according to Nakamura, is the lack of a bulk substrate for gallium nitride crystalline growth. Current blue-laser diode fabrication uses a freestanding GaN substrate that is epitaxially grown on a sapphire substrate, with the sapphire substrate removed once the thick GaN layer is formed. But substrates made using this process include a high number of dislocations, or defects. [Nakamura is the father of GaN blue laser diode]
A lateral epitaxially overgrown method is widely used to grow GaN films with fewer defects, but this method often results in a mixture of high- and low-quality crystalline. As a result, only about half of the diodes on a wafer can be used as lasers. Worse, the substrates are subject to bowing, making it difficult to expose light uniformly on them during photolithography and thus further reducing yield.
"The ultimate solution to achieving high yields is to develop a bulk substrate for GaN," said Nakamura, adding that his team and others are doing research in that area. "Until such a genuine substrate is developed, it should be difficult to raise yields using current pseudosubstrates."
Other semiconductor lasers, such as the red laser diodes used in CD and DVD players and recorders, once faced similar yield problems, which were overcome when production efforts expanded, according to Nakamura. But that was a very different situation, he cautioned, because suitable substrates were already available.
"Executive officers without a technical background may think that the situation is the same and direct engineers to go forward," Nakamura said. "But the situation is different. There is no suitable substrate."
The metal-organic chemical vapor deposition (MOCVD) systems used in blue-laser diode production also pose a problem, Nakamura said. "The companies developing [blue] lasers are using their uniquely tuned systems," he said. "As far as I know, those MOCVD systems are not suitable for batch processing." [MOCVD: is invention of Nakamura while working at Nichia]
Sony Corp.'s Shiroishi fab is in charge of supplying the blue-laser diodes for the Playstation 3. Volume production at that fab is going online now. Sony installed multiple MOCVD systems to expedite production, a spokesman said, but "it was difficult to control these systems to grow uniform, high-quality crystalline films. It took time to improve the yield rate."
Sony Computer Entertainment plans to ship 1 million Playstation 3 units into the Japanese market and more than 1 million into the U.S. market by the end of this year. The company expects to begin delivering PS3s to the European market by the spring. If all goes according to plan, Sony will ship 6 million units by March.
"The fab is concentrating its resources and efforts to produce sufficient diodes in time" for that schedule, said a Sony spokesman, expressing confidence that the volume targets would be reached.
Robert Steele, an analyst with Strategies Unlimited (Mountain View, Calif.), said it's fair to say Sony has exorcised its blue-laser demons, given that the company has shipped nearly 500,000 PS3 units this month. "Once you can get to the point where you are making tens of thousands and hundreds of thousands, you've probably got the problem under control," Steele said. "But that doesn't mean it's easy."
Meanwhile, it appears as though one company with a long history of blue-laser diode work may have thrown in the towel, or at least scaled back R&D on the project. A spokeswoman for Cree Inc. (Durham, N.C.) initially told EE Times that the company was no longer developing blue-laser diodes. In a follow-up e-mail she said the company was still working on the technology but could not "discuss this effort at this point."
Cree, which markets chips for LED solid-state lighting, power and communications, has been conducting blue-laser diode R&D since the early 1990s but has never offered a commercial product. As far back as 1995, Cree was publicizing the prototype development of a superbright blue LED made from GaN and silicon carbide. At one point, Cree had been receiving funding from the Defense Advanced Research Projects Agency for blue-laser diode development. Last year Cree was awarded a $26.9 million Darpa contract along with Raytheon Co. to develop GaN chips, but it is unclear whether Cree is still being funded for work on blue lasers.
Cree's most recent annual report, for the fiscal year ended June 25, stated that the company was working with a partnerknown to be Japan's Rohm Corp.to commercialize the technology. A subsequent regulatory filing for the quarter ended Sept. 24 does not reference the project.
According to Strategies Unlimited's Steele, Cree used to discuss the blue-laser diode R&D project in every quarterly financial conference call but has stopped talking about it over the past few quarters. Cree had never been very forthcoming with details about the project, but neither has it ever explicitly said it has ceased development, Steele said. He speculated that the company has put the project "on the back burner."
"Since[the project is] not going to turn into money anytime soon-and they certainly have products that are generating short-term revenue-I could kind of understand them de-emphasizing it if the progress has been slow," Steele said.
By contrast, several Japanese companies remain aggressive in developing blue-laser diodes. Sharp Corp. has become the third blue-laser producer, having recently started volume production at its Mihara fab, which is dedicated to LED and laser production. Sharp's laser has 20-mW output for read-only applications.
Sharp tapped its previous work on epitaxial growth technology for infrared and red lasers to reduce the number of cracks in the GaN crystalline used for the blue lasers, according to a spokesman.
The combination of the chip design and the epitaxial growth technology enabled a laser with a 10,000-hour lifetime and 168-mW power consumption, the spokesman said. The company has a startup capacity of 150,000 units per month. Sharp is also developing a high-power, pulsed-wave blue laser that will output 130 to 210 mW.
Nichia Corp., currently the sole merchant supplier of blue lasers, has not disclosed its production capacity or ramp-up plans. "We are supplying the laser diodes to limited customers, so we have not been publicizing details of our production plan, but we are preparing a big expansion in production," said a Nichia spokesman.
Both next-generation DVD formatsHD-DVD and Blu-ray Disc, the format chosen for the PS3rely on blue-laser diodes. All HD-DVD and Blu-ray products except Sony's currently employ Nichia's laser diodes.
Sony earlier this year pushed back the U.S. introduction of a Blu-ray Disc player from July to autumn. The player has still not hit the market, and Sony has not readjusted its timetable.
According to the Sony spokesman, the delay is not related to laser diode production but to software development.
Toshiba is the sole HD-DVD hardware supplier at present, is offering players, recorders and PC drives and supplying a drive for Microsoft's Xbox 360 on an OEM basis. Shinichi Ito, senior manger of the digital AV division of Toshiba, said the company has had no laser diode supply problems and is "not worried about the supply at all."
Toshiba is working on developing in-house blue-laser capability, as are Sanyo Electric Co. Ltd. and NEC Corp. None of the three has commenced production.
Its easy to berate Sony, criticize Sony for pushing Blu-ray and singing praise of MS for 360 but without Sony pushing the GaN process technology we would not have Blue laser diode becoming prevalent. Sony is the second company to manufacture after Nichia, even Toshiba which is supporting HD-DVD does not manufacture Blue laser diode.[/b
