Electrical Properties of GaN/Si Grown by MOCVD
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L3.23.1
Electrical Properties of GaN/Si Grown by MOCVD Seikoh Yoshida, Jiang Li, Takahiro Wada, and Hironari Takehara Yokohama R&D Laboratories, The Furukawa Electric Co., Ltd 2-4-3, Okano, Nishi-ku, Yokohama, 220-0073, Japan ABSTRACT GaN growth on Si substrate is very attractive for realizing low cost electronic devices. We grew a thin GaN film on p-type Si (111) substrate using AlGaN high temperature buffer without using a conventional low temperature buffer. A homogeneous buffer layer was obtained at 1093 K and a homogenous 500 nm thick GaN layer was also obtained without any crack. Using a transmission electron microscopy (TEM), we observed that the cross-section of GaN and AlGaN buffer was very smooth and also the surface of GaN was flat although the threading dislocations were observed. Furthermore, we directly fabricated a metal semiconductor field effect transistor (MESFET) using a 500 nm-thick GaN/Si without any high resistive GaN layer. A Schottky electrode was Pt/Au and an ohmic electrode was Al/Ti/Au. A Schottky breakdown voltage was over 100 V. Also, we confirmed a high temperature operation of the MESFET using a thin GaN film on Si substrate at 573 K. INTRODUCTION III-V nitrides are very promising for high-power, high-frequency, and high-temperature devices [1-8]. GaN and related materials are generally grown using sapphire or SiC substrates. For low-cost device fabrication, a Si substrate is very useful. Si substrates for GaN growth have several advantages compared with other substrates: they can be obtained at low cost, and high-quality Si wafers with a large diameter can be easily obtained. A high-quality very thin GaN film on a Si substrate is required for electronic devices of low-cost mass production. The growth of GaN on Si is very difficult due to the difference of the lattice constant and the thermal-expansion coefficient, resulting in the occurrence of cracks in GaN. Recently, good-quality GaN on a Si substrate has been reported [9-13]. An AlGaN/GaN heterojunction field effect transistor (HFET) on a Si substrate has been reported. However, there is no report concerning electronic devices such as FETs or Schottky barrier diodes (SBDs) using a thin film GaN below 1000 nm in thickness including high resistive GaN layers on Si substrate. Our purpose is to fabricate electronic devices using very thin GaN and related materials on a Si substrate in order to fabricate low-cost devices. In this paper, we report that by using an AlGaN buffer, a crack free GaN was obtained on a Si (111) substrate, and that a metal field effect transistor (MESFET) with a breakdown voltage over 100V for a high temperature operation at 573 K was obtained using a 500 nm-thick GaN film on a Si (111) substrate.
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EXPERIMENTAL We first tried to grow GaN without cracking on a 2-inches p-type Si (111) substrate using metal-organic chemical vapor deposition (MOCVD) in order to fabricate a MESFET using a thin GaN film on the Si substrate. Trimethylgallium (TMG), trimethylaluminium (TMA), and ammonia (NH3) were used for s
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