High Power AlGaN/GaN Schottky Barrier Diode with 1000 V Operation
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0892-FF05-02.1
High power AlGaN/GaN Schottky Barrier Diode with 1000 V operation Seikoh Yoshida, Nariaki Ikeda, Jiang Li, Takahiro Wada, Hiroshi Kambayashi, and Hironari Takehara 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 Schottky barrier diode (SBD) with a field plate structure for a high breakdown voltage. The AlGaN/GaN heterostructure was grown by MOCVD. The AlGaN buffer was grown on the Si (111) substrate and Al0.25Ga0.75N (25 nm)/ GaN (1000 nm) was grown on the buffer layer. The AlGaN/GaN heterostructure without any crack was obtained. After that, a Schottky barrier diode was fabricated using an AlGaN/GaN heterostructure. In order to obtain a high breakdown voltage, a gate field plate structure was used. SiO2 was formed on the AlGaN layer using a plasma chemical vapor deposition. The Schottky electrode of Ni/Au was partially deposited on the SiO2 film towards the ohmic region. The length of field plate structure was also changed to investigate the effect. Ti/Al-silicide was used for an ohmic electrode of SBD. The contact resistance of ohmic electrodes was 8E-6 ohmcm2. The current-voltage characteristics of an AlGaN/GaN SBD were measured. The reverse breakdown voltage of the diode was also over 1000 V and the reverse leakage current was below 1.5E-6 A/mm. INTRODUCTION III-V nitride based electronic devices are excellent for high power, high frequency and high temperature devices [1-11]. For realizing the high efficiency switching devices such as inverters or converters, not only FETs with a low on-state resistance, but also, a Schottky barrier diode with a high breakdown voltage and a high switching speed are also necessary. The GaN based Schottky barrier diode (SBD) is expected to have a high switching speed. However, for realizing a high efficiency inverter, not only FETs with a low on-state resistance, but also, a freewheel diode with a very low on-voltage and a very small recovery time is required to immediately cut off the freewheeling current. The GaN is also effective for a fast recovery diode or
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freewheeling diode, since they have a very high switching speed, and a very low recovery charge. We recently proposed a field effect Schottky barrier diode (FESBD) with dual Schottky metal structures for realizing a low on-voltage and demonstrated the FESBD with an on-voltage of 0.1 V and a breakdown voltage of 400 V [12-15]. In this paper, we investigated the SBD having a further high breakdown voltage and report on an AlGaN/GaN SBD with a high breakdown voltage of over 1000V and its high temperature operation at 573 K. EXPERIMENTAL PROCEDURE An AlGaN/GaN heterostructure was grown using a metal-organic chemical vapor deposition (MOCVD). A Si (111) substrate with a two-inch size was used to realize a low cost device. Trimethylgallium (TMG), trimethylaluminium (TMA), and ammonia (NH3) were used for source gases of the GaN growth. An AlGaN based buffer layer was grown on the Si substrate. An Al
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