Site: NEC Optoelectronics Research Laboratories
34 Miyukigaoka, Tsukuba
Ibaraki 305, Japan

Date Visited: December 12, 1994

Report Author: L. Coldren

ATTENDEES

JTEC:

L. Coldren
M. DeHaemer

HOSTS:

Dr. Ikuo Mito
Senior Manager, Optoelectronic Device Research Lab
Dr. Kiyoshi Asakawa
Senior Research Specialist reporting directly to K. Kobayashi (formerly Senior Manager, OE Basic Research Lab)
Dr. Kenichi Kasahara
Manager, Basic Research, OE Basic Research Lab (former Senior Mgr., OE Basic Research Lab)
Dr. Kenko Taguchi
Sr. Manager, Basic Research, OE Device Research Lab

Dr. K. Kobayashi, General Manager of NEC OE Research Labs, kindly arranged the visit, although he was unable to be present.

BACKGROUND

NEC's current motto of "C&C for human potential" is so ingrained that one can read through several of the company's brochures without finding the abbreviation "C&C" even defined. The integration of computers and communication is the basis for NEC's business activities. Major product areas are listed as (1) communications systems and equipment, (2) computers and industrial electronic systems, and (3) electron devices. Sales percentages are listed as 27%, 50%, and 18%, respectively, in these three areas. Consumer electronics accounts for the balance of about 5%. International activities account for 24% of the total sales. NEC has 8 major plants near Tokyo, 55 subsidiaries in Japan, and 33 others in 16 countries worldwide. R&D facilities include 5 facilities in Japan and the NEC Research Institute in the United States. About 7% of sales go to support R&D expenses.

In fiscal 1994 (ending March 31), NEC had sales of $35 billion but a net income of only $65 million. Over the past several years, profits have declined, as have those of many Japanese companies. In 1994 NEC showed a net loss of about $450 million. The company expects profits to increase slowly over the next few years, again paralleling the general economic recovery in Japan.

NEC is organized into eleven operating groups. In this visit to Tsukuba Optoelectronics Research Labs, the JTEC panel visited elements of the Research & Development Group. The technology transfer between these entities is one key aspect of the panel's study.

The Research & Development Group is responsible for creating C&C core technologies and identifying new areas for high-tech products. It consists of a vast array of different laboratories and centers spread across six locations. Tsukuba houses elements of the Fundamental Research Labs, the Microelectronics Research Labs, and the Optoelectronics Research Labs. Dr. Kohroh Kobayashi is currently General Manager of the OE Research Labs. His office is at the Central Research Labs in Kawasaki. About 80 of the 150 OE Research Labs members work in Tsukuba in either the OE Basic Research or OE Device Research Labs.

DISCUSSION

The JTEC panel's host for the visit was Dr. Ikuo Mito, Senior Manager of the OE Device Research Lab. He outlined the company's general activities, and Drs. Kenichi Kasahara and Kiyoshi Asakawa discussed some of the work of the OE Basic Research Lab. Afterward, the panel members toured the lab and finished with more general discussion of NEC's business interests and technology transfer procedures.

Dr. Mito's introduction included a strong indication that the company was moving toward home and business multimedia applications with a target of 50% of sales by 1999. He reviewed a program focused on interconnection, including experiments on plastic optical fiber (POF) at 650 nm with lasers and 570 nm with LEDs. He also discussed the lab's interest in 980 nm data links using plastic-clad glass fiber (PCF). All work at the time of the JTEC visit was using edge-emitters, but VCSELs were being developed for the 980 nm case. A 100-meter-long 2.5 Gbit/s data link experiment had been completed with graded-index POF at 650 nm. This graded-index POF was generating a lot of excitement. GaAs detectors and Si pins are possible detectors, but the GaAs is preferred, since the bias voltage is too high with silicon. Single lines as well as one-dimensional arrays are being pursued for parallel data links. Very large core fibers also look attractive for low-cost packaging. The main difficulties are reducing the device costs and obtaining low-loss plastic fiber.

For the 980 to 950 nm data links, VCSEL arrays are being researched, although edge-emitters appear to be workable. The interest is mainly because of the high-efficiency, high-temperature performance (high T 0 ), and the ability to use zero-bias drive circuits. Despite difficulties in using Si detectors, the research seems to be focused on using a low-voltage Si pin for this application. Thus, the wavelength may need to become a little shorter than 980 nm. Low cost packaging is a focus. Plastic encapsulation will be used. Applications in computer interconnection between and within boards as well as between boxes with fiber channel are perceived for Video on Demand (VOD). An example was also given of a computer application containing 8 processors with 4 ports each 72 bits wide at 50 Mbit/s.

VCSELs are also being explored in the OE Basic Lab by Dr. Kasahara's group for optical switching and computing applications. His work on the "VSTEP" is well known. This is basically a VCSEL in series with a pnpn diode to provide latching, so that once pulsed on, the device continues to emit until reset. Applications are not well defined for this technology.

The transfer of technology from Tsukuba to the factory at Kansai was discussed at some length. Generally, most technology is transferred without a permanent transfer of people. However, about 10 of the 150 OE Research Labs' researchers are spending time in the development and manufacturing plants, on average. The output of their research generally connects to the efforts at the ULSI Device Development lab (in the Semiconductor Group) or directly to the Optical Group in the Compound Semiconductor Device Division. There are also close interactions with NEC's Transmitter Group.

Over the past ten years, about 80% of the device projects carried to maturity in the OE Device Research Lab have generated products for NEC. The panel's hosts listed as successes InGaAsP/InP-LDs, Dets, and APDs; AlGaInP/GaAs-LDs at visible; and Ge APDs. Listed as failures were AlGaAs LDs and OEICs. Still in question are PICs and InGaAlAs/InP APDs. An integrated DFB-mod is under codevelopment with Kansai engineers.

Funding for research comes from contracts with the production division (30%) and headquarters (70%). Of the total R&D listed by NEC, only about 10% (or 1% of NEC sales) actually goes to the R&D Group -- the rest goes to the product development groups.

The lab tour illustrated several OMVPE machines of home design and gas-source MBE for optical device growth. The JTEC team members also observed the usual processing equipment and learned about the lab's work on AlPSb/GaPSb for DBR mirrors on InP grown by gas-source MBE in the OE Basic Lab. Because of the larger impedance discontinuity, NEC scientists claimed that mirrors with comparable reflectivity to the GaAs/AlAs mirrors could be grown on InP. These may enable practical VCSELs on InP.

Future activities cited include 630 nm lasers (in about one year), continued work with blue-green lasers; and semiconductor optical amplifiers. For future progress, NEC researchers cite the need for control circuits for tunable lasers; low-cost packaging; improved patterned growth; and a better tunable laser-modulator. (The researchers have plans for arrays of integrated DBR-mods joined into a common waveguide.)

SUMMARY

The 80 researchers at the NEC-Tsukuba location comprise a little more than half of the NEC Optoelectronics Research Labs, currently directed by Dr. K. Kobayashi. Others reside at the Central Research Labs in Kanagawa. In addition to the basic work on short- and long-wavelength VCSELs in the basic lab, the focus of the OE Device Lab (under Dr. Mito) seemed to be on simple data links for on-premises multimedia applications. For its optical interconnection thrust, NEC-Tsukuba seems to have a strong focus on plastic fiber (perhaps graded index) using 650 nm sources, and on plastic-clad glass fiber using 980 nm sources. Edge-emitters were viewed as satisfactory for all of these applications, although if cost reductions might be possible with VCSELs, they would be pursued vigorously. Low-cost packaging using plastic encapsulation was a complementary thrust. Video-on-demand was listed as an additional application for VCSELs for either intra- or inter-computer interconnections

REFERENCES

Company Brochures

NEC Corporation. 1994. This is NEC. (Available from NEC, 7-1, Shiba 5-chome, Minato-ku, Tokyo, Japan).
_____. 1994. NEC Research and Development. (Available from NEC Research and Development Group, Kawasaki, Kanagawa 216, Japan).

Publications

S. Shimomura et al. 1994. Electron. Lett. 30 (4) 314.
K. Mori et al. 1994. Electron. Lett. 30 (12) 1008.
H. Hotta et al. 1993. Presented at Int. Symp. GaAs and Related Compounds Proc., Freiburg.
T. Sasaki et al. 1993. J. Crystal Growth 132, 435.
S. Ishikawa et al. 1993. J. Quantum Electron. 29 (6) 1936.
K. Endo et al. 1994. Appl. Phys. Lett. 64 (2) 146.


Published: February 1996; WTEC Hyper-Librarian