Fabrication of AlGaN/GaN HFET with a High Breakdown Voltage on 4-inch Si (111) Substrate by MOVPE
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0955-I16-06
Fabrication of AlGaN/GaN HFET with a High Breakdown Voltage on 4-inch Si (111) Substrate by MOVPE Yuki Niiyama, Sadahiro Kato, Yoshihiro Sato, Masayuki Iwami, Jiang Li, Hironari Takehara, Hiroshi Kambayashi, Nariaki Ikeda, and Seikoh Yoshida Yokohama R&D Laboratories, The Furukawa Electric, Co., Ltd., 2-4-3, Okano, Nishi-ku, Yokohama, 220-0073, Japan
ABSTRACT We investigated an AlGaN/GaN heterostructure field effect transistor (HFET) on Si substrates using a multi-wafer metalorganic vapor phase epitaxy (MOVPE) system. It was confirmed that a GaN film with smooth surface and without any crack was obtained. To increase a resistance of a GaN buffer layer, the carbon (C) -doping was carried out by controlling the V/III ratio and the growth pressure. The breakdown voltage of the buffer layer was dramatically improved by introducing the C. As a result, the breakdown voltage was about 900 V when the C concentration was ~8x1018 cm-3. After while, an AlGaN/GaN heterojunction FET (HFET) on a C-doped GaN buffer layer was fabricated. We achieved the breakdown voltage of over 1000 V and the maximum drain current of over 150 mA/mm, respectively. It was found that the C doped buffer layer is very effective for improving the breakdown voltage of AlGaN/GaN HFETs.
INTRODUCTION GaN based electronic devices are very promising for high power, high frequency and high temperature devices due to having the excellent figure of merits [1,2]. For achieving the high efficiency switching devices such as inverters or converters, field effect transistors (FETs) with a low on-state resistance, high breakdown voltage and high switching speed are required. The AlGaN/GaN heterojunction field effect transistor (HFET) is a good candidate of the power and high-speed devices. In addition, the power devices are strongly required to be low cost. To reduce the cost of devices, a Si substrate is very useful for the GaN growth because it is definitely low price. However, the crystal growth of GaN on Si substrate is very difficult due to the difference in lattice constant and thermal expansion coefficient. Up to now, AlGaN/GaN heterojunction field effect transistors (HFETs) on Si substrates have been reported [3-8]. However, these device characteristics should be moreover improved. We previously fabricated an AlGaN/GaN HFET on a 2-inch Si substrate and demonstrated high breakdown voltages of more than 400 V at the off-state [9]. However, it is necessary to develop the growth technology using large diameter substrates in a multi-wafer reactor for mass production, since GaN epitaxial wafers with a large diameter enable us to realize large size devices and they can be soon applied to conventional manufacture lines for Si devices. In this paper, we demonstrate that the GaN heterostructure was grown on a 4-inch Si (111) substrate by metal-organic vapor phase epitaxy (MOVPE) and that the breakdown voltage of an AlGaN/GaN HFET was over 1000 V.
EXPERIMENT We have used five 4-inch wafers (5x4”) MOVPE system for AlGaN/GaN epitaxial growth. Trimethylgall
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