High Temperature Operation of A New Normally-Off AlGaN/GaN HFET on Si Substrate
- PDF / 874,989 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 8 Downloads / 153 Views
Y7.3.1
High Temperature Operation of A New Normally-Off AlGaN/GaN HFET on Si Substrate 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 We report on the novel normally-off AlGaN/p-type GaN heterojunction field effect transistors (HFETs). We grew the AlGaN/p-GaN heterostructure on p-type Si (111) substrate using a metalorganic chemical vapor deposition (MOCVD). A homogeneous buffer layer was first formed on a Si (111) substrate at 1123 K. After that, AlGaN (30 nm)/high resistive p-type GaN (500 nm) heterostructure was also grown at 1303 K without cracking. We fabricated an HFET using AlGaN/p-type GaN on Si substrate. The ohmic electrode material was Al/Ti/Au and the gate electrode was Pt/Au. The distance between the source and the drain was 0.01 mm. The gate length and width were 2000 nm and 0.15 mm, respectively. As a result, the HFET was operated at the condition of the positive gate bias. The pinch-off voltage was 0 V. A normally-off operation was thus confirmed for the first time. The breakdown voltage of FET was over 250 V. We also confirmed that the normally-off HFET was operated at 573 K for over 150 h. INTRODUCTION GaN and related materials are very attractive for high-power, high-frequency, and high-temperature devices [1-5]. The GaN is conventionally grown using sapphire or SiC substrates. For low-cost device fabrication, a Si substrate is very useful due to the low cost, and high-quality Si wafers with a large diameter can be easily obtained. 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 [6,7]. An AlGaN/GaN heterojunction field effect transistor (HFET) on a Si substrate has been reported. Also, we reported that a GaN based metal semiconductor field effect transistor (MESFET) and an HFET using a Si substrate [8-10]. However, until now, GaN based FETs, which have been reported, are almost normally-on type FETs. A normally-on type FET is not so convenient for switching device such as an inverter or a converter, since the switching circuit is complicated. For switching devices such as an inverter or converter, a normally-off type FET with a low on-state resistance is required. There are very few reports for a normally-off FET using GaN and related materials [11]. In this paper, we report on three types of normally-off type FETs using AlGaN/p-GaN on Si (111) substrate.
Y7.3.2
EXPERIMENTAL A p-type Si (111) substrate with a two-inches size was used for the growth. An AlGaN/GaN heterostructure was grown using a metal-organic chemical vapor deposition (MOCVD). Trimethylgallium (TMG), trimethylaluminium (TMA), Cp2Mg (p-type dopant) and ammonia (NH3) were used for source gases. The C-doping is performed by controlling a reactor pressure and V/III ratio. A thin AlGaN buffer was used for GaN growth.
Data Loading...
