INTRODUCTION

The Furukawa Electric Co. Ltd. was founded in 1884 and reorganized in 1920. Its present sales amount to ¥56.6 billion (approximately $400 million), and it has 10,000 employees. Its major business activities include many industrial and consumer products, such as electric and magnetic, superconducting and optical fiber cables, automotive parts and accessories, metal alloys, electronic and optical materials, components and system products. Its R&D activities can be divided into 5 categories:

1. information systems centering on optical technology


2. electronics exploration progressing rapidly into even wider ranges of applications


3. new materials and functions


4. energy studies to support the foundations of industrial development


5. advanced automotive electric equipment and parts

The Yokohama R&D Laboratories is one of Furukawa's 7 research laboratories and has been at its present location since 1987. The lab has about 300 employees and occupies a total land area of 22,000 m².

STATUS OF ACTIVITIES

Furukawa Electric is a subsidiary of the Furukawa group, which also includes the Fuji Electric and Fujitsu. Fuji Electric is a major supplier of silicon power device modules, and Fujitsu is a major computer and integrated circuit company. Furukawa's products include many industrial and consumer products, like superconducting cables, memory alloys, optical devices and modulators. Four engineers, including Dr. Yoshida, discussed the technical details of the program and answered most of the TTEC panel's inquiries. Furukawa is interested in both GaN and SiC.

Furukawa has been conducting epitaxial growth of GaN on sapphire substrates since 1986 using gas source MBE. One reason for using MBE as the growth method is that Furukawa had already been using GaAs MBE for many years. Furukawa's interests in GaN include optical laser diodes as well as high frequency, high voltage power devices. Additionally, it would like to serve as a GaN epi supplier to other companies (within its group). It has a load-lock MBE system that utilizes DMHydrazine and NH₃ as precursors. Dr. Yoshida and Dr. Suzuki commented that the growth of GaN on silicon is difficult because the film is under tension and often cracks. Their growth experiments have been mostly done on 2-inch substrates. No growth has been observed at temperatures below 800° C with these precursors. A typical FWHM of 50 arcsec has been measured, indicating very high quality epi layers. The FWHM is even sharper when undoped layers are grown with a V/III precursor ratio increased by a factor of 3 and a substrate temperature of 850° C. Photoluminescence (PL) measurements of InGaN films with a 1% indium concentration indicate that the commonly observed yellow band emission in GaN is absent. Mg-doped GaN films exhibit a sharp 430-nm emission, but again an emission in the yellow wavelengths. Typical hole concentrations are in the 1-2x10¹⁷ /cm³ range at room temperature. GaN was etched in ECR plasma with CH₄/Ar/H₂ (15:7:5). Mg-doped films are etched twice as slowly as undoped or Si-doped films. AlGaN films are etched at a 40% slower rate. A selectivity of about 10 has been obtained over SiO₂.

These process technologies have been employed to fabricate a lateral MESFET that is capable of withstanding high temperatures. Pt-gate GaN MESFET with oxide passivation has been tested up to 500° C. After 500° C annealing, a high gate-to-source leakage appears. Tungsten (with a small percentage of silicon) has also been tried as the Schottky gate, but the device fails after 500° C treatment. Schottky gate reliability testing at 400° C for 900 hours results in substantial degradation in gate-to-drain leakage. Ti/Al ohmic contact stressing at 550° C has shown no change in the abrupt interface. Besides MESFET, GaN MISFETs with AlN as a gate insulator have been fabricated and yield BV larger than 100 V. A GaiV rpn bipolar junction transistor has also been operated at 300°C.

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