Tetsuzo Ueda

Bio: Tetsuzo Ueda is an academic researcher from Panasonic. The author has contributed to research in topics: Layer (electronics) & Transistor. The author has an hindex of 42, co-authored 308 publications receiving 7445 citations. Previous affiliations of Tetsuzo Ueda include New Energy and Industrial Technology Development Organization & Stanford University.

GaN-on-Si Power Technology: Devices and Applications

Abstract: In this paper, we present a comprehensive reviewand discussion of the state-of-the-art device technology and application development of GaN-on-Si power electronics. Several device technologies for realizing normally off operation that is highly desirable for power switching applications are presented. In addition, the examples of circuit applications that can greatly benefit from the superior performance of GaN power devices are demonstrated. Comparisonwith other competingpower device technology, such as Si superjunction-MOSFET and SiC MOSFET, is also presented and analyzed. Critical issues for commercialization of GaN-on-Si power devices are discussed with regard to cost, reliability, and ease of use.

Gate Injection Transistor (GIT)—A Normally-Off AlGaN/GaN Power Transistor Using Conductivity Modulation

Abstract: We have developed a normally-off GaN-based transistor using conductivity modulation, which we call a gate injection transistor (GIT). This new device principle utilizes hole-injection from the p-AlGaN to the AlGaN/GaN heterojunction, which simultaneously increases the electron density in the channel, resulting in a dramatic increase of the drain current owing to the conductivity modulation. The fabricated GIT exhibits a threshold voltage of 1.0 V with a maximum drain current of 200 mA/mm, in which a forward gate voltage of up to 6 V can be applied. The obtained specific ON-state resistance (RON . A) and the OFF-state breakdown voltage (BV ds) are 2.6 mOmega . cm2 and 800 V, respectively. The developed GIT is advantageous for power switching applications.

GaN on Si Technologies for Power Switching Devices

Abstract: This paper reviews the recent activities for normally-off GaN-based gate injection transistors (GITs) on Si substrates and their application to inverters. Epitaxial growth of the AlGaN/GaN heterostructures with good crystallinity over 200-mm Si substrates with eliminated bowing enables low-cost fabrication of GaN devices with high breakdown voltages. A novel normally-off GaN transistor called as GIT is proposed in which hole injection from the p-type AlGaN gate increases the drain current with low on-state resistance by conductivity modulation. The low on-state resistance in GaN-based devices greatly helps to increase the efficiency of power switching systems. A GaN-based three-phase inverter successfully drives a motor with high efficiency of 99.3% at a high output power of 1500 W. The presented GaN-based devices are expected to greatly help saving energy in the future as an indispensable power switching system.

Nitride semiconductor device

Abstract: A nitride semiconductor device includes: a first semiconductor layer made of first nitride semiconductor; a second semiconductor layer formed on a principal surface of the first semiconductor layer and made of second nitride semiconductor having a bandgap wider than that of the first nitride semiconductor; a control layer selectively formed on, or above, an upper portion of the second semiconductor layer and made of third nitride semiconductor having a p-type conductivity; source and drain electrodes formed on the second semiconductor layer at respective sides of the control layer; a gate electrode formed on the control layer; and a fourth semiconductor layer formed on a surface of the first semiconductor layer opposite to the principal surface, having a potential barrier in a valence band with respect to the first nitride semiconductor and made of fourth nitride semiconductor containing aluminum.

Field effect transistor and method for fabricating the same

Abstract: An AlN buffer layer, an undoped GaN layer, an undoped AlGaN layer, a p-type GaN layer and a heavily doped p-type GaN layer are formed in this order. A gate electrode forms an Ohmic contact with the heavily doped p-type GaN layer. A source electrode and a drain electrode are provided on the undoped AlGaN layer. A pn junction is formed in a gate region by a two dimensional electron gas generated at an interface between the undoped AlGaN layer and the undoped GaN layer and the p-type GaN layer, so that a gate voltage can be increased.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Light-emitting diodes

Abstract: Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Light passing through subwavelength apertures

Abstract: This review provides a perspective on the recent developments in the transmission of light through subwavelength apertures in metal films. The main focus is on the phenomenon of extraordinary optical transmission in periodic hole arrays, discovered over a decade ago. It is shown that surface electromagnetic modes play a key role in the emergence of the resonant transmission. These modes are also shown to be at the root of both the enhanced transmission and beaming of light found in single apertures surrounded by periodic corrugations. This review describes both the theoretical and experimental aspects of the subject. For clarity, the physical mechanisms operating in the different structures considered are analyzed within a common theoretical framework. Several applications based on the transmission properties of subwavelength apertures are also addressed.

Comparison of 6H-SiC, 3C-SiC, and Si for power devices

Abstract: The drift region properties of 6H- and 3C-SiC-based Schottky rectifiers and power MOSFETs that result in breakdown voltages from 50 to 5000 V are defined. Using these values, the output characteristics of the devices are calculated and compared with those of Si devices. It is found that due to very low drift region resistance, 5000-V SiC Schottky rectifiers and power MOSFETs can deliver on-state current density of 100 A/cm/sup 2/ at room temperature with a forward drop of only 3.85 and 2.95 V, respectively. Both devices are expected to have excellent switching characteristics and ruggedness due to the absence of minority-carrier injection. A thermal analysis shows that 5000-V, 6H-, and 3C-SiC MOSFETs and Schottky rectifiers would be approximately 20 and 18 times smaller than corresponding Si devices, and that operation at higher temperatures and at higher breakdown voltages than conventional Si devices is possible. Also, a significant reduction in the die size is expected. >