Two layers of protection films are formed such that a sheet resistance at a portion directly below the protection film is higher than that at a portion directly below the protection film. The protection films are formed, for example, of SiN film, as insulating films. The protection film is formed to be higher, for instance, in hydrogen concentration than the protection film so that the protection film is higher in refractive index the protection film. The protection film is formed to cover a gate electrode and extend to the vicinity of the gate electrode on an electron supplying layer. The protection film is formed on the entire surface to cover the protection film. According to this configuration, the gate leakage is significantly reduced by a relatively simple configuration to realize a highly-reliable compound semiconductor device achieving high voltage operation, high withstand voltage, and high output.

Compound semiconductor device and method of manufacturing the same

We evaluate and compare the performance and potential of GaAs and of wide and extreme bandgap semiconductors (SiC, GaN, Ga2O3, and diamond), relative to silicon, for power electronics applications. We examine their device structures and associated materials/process technologies and selectively review the recent experimental demonstrations of high voltage power devices and IC structures of these semiconductors. We discuss the technical obstacles that still need to be addressed and overcome before large-scale commercialization commences.

Smart Power Devices and ICs Using GaAs and Wide and Extreme Bandgap Semiconductors

In this paper, recent advances of GaN transistors on Si for switching and high-frequency applications are reviewed. Novel epitaxial structures including superlattice interlayers grown by metal organic chemical vapor deposition (MOCVD) relieve the strain and eliminate the cracks in the GaN over large-diameter Si substrates up to 8 in. As a new device structure for high-power switching application, Gate Injection Transistors (GITs) with a p-AlGaN gate over an AlGaN/GaN heterostructure successfully achieve normally-off operations maintaining high drain currents and low on-state resistances. Note that the GITs on Si are free from current collapse up to 600 V, by which the drain current would be markedly reduced after the application of high drain voltages. Highly efficient operations of an inverter and DC–DC converters are presented as promising applications of GITs for power switching. The high efficiencies in an inverter, a resonant LLC converter, and a point-of-load (POL) converter demonstrate the superior potential of the GaN transistors on Si. As for high-frequency transistors, AlGaN/GaN heterojuction field-effect transistors (HFETs) on Si designed specifically for microwave and millimeter-wave frequencies demonstrate a sufficiently high output power at these frequencies. Output powers of 203 W at 2.5 GHz and 10.7 W at 26.5 GHz are achieved by the fabricated GaN transistors. These devices for switching and high-frequency applications are very promising as future energy-efficient electronics because of their inherent low fabrication cost and superior device performance.

https://iopscience.iop.org/article/10.7567/JJAP.53.100214/pdf

GaN transistors on Si for switching and high-frequency applications

The objectives of this paper are to propose a method that can accurately estimate the human heart rate (HR) using an ultrawideband (UWB) radar system, and to determine the performance of the proposed method through measurements. The proposed method uses the feature points of a radar signal to estimate the HR efficiently and accurately. Fourier- and periodicity-based methods are inappropriate for estimation of instantaneous HRs in real time because heartbeat waveforms are highly variable, even within the beat-to-beat interval. We define six radar waveform features that enable correlation processing to be performed quickly and accurately. In addition, we propose a feature topology signal that is generated from a feature sequence without using amplitude information. This feature topology signal is used to find unreliable feature points, and thus, to suppress inaccurate HR estimates. Measurements were taken using UWB radar, while simultaneously performing electrocardiography measurements in an experiment that was conducted on nine participants. The proposed method achieved an average root-mean-square error in the interbeat interval of 7.17 ms for the nine participants. The results demonstrate the effectiveness and accuracy of the proposed method. The significance of this study for biomedical research is that the proposed method will be useful in the realization of a remote vital signs monitoring system that enables accurate estimation of HR variability, which has been used in various clinical settings for the treatment of conditions such as diabetes and arterial hypertension.

/pdf/feature-based-correlation-and-topological-similarity-for-1e4gbwi31g.pdf

Feature-Based Correlation and Topological Similarity for Interbeat Interval Estimation Using Ultrawideband Radar

In this letter, high-output-power-density GaN-based high-electron-mobility transistors grown on a 100-mm silicon substrate is demonstrated for the first time at 40 GHz The use of an optimized double heterostructure based on ultrathin barrier AlN/GaN allows both high current density and low leakage current, resulting in high-frequency performance (fmax close to 200 GHz) Furthermore, the control of the trapping effects on these highly scaled devices enabled to set a first benchmark at 40 GHz with 25 W/mm at VDS = 15 V, mainly limited by RF losses and thermal issues These results show that an AlN/GaN/AlGaN heterostructure grown on silicon substrate is a viable technology for cost-effective high-power millimeter-wave amplifiers fully compatible with standard Si-based devices

First Demonstration of High-Power GaN-on-Silicon Transistors at 40 GHz

Outstanding GaN-based HFETs (HFET: Heterojunction Field-Effect Transistors) [1] power devices are expected to replace all Si power devices in high power applications such as inverter systems due to their excellent performance In order to exploit the full potential of such emerging GaN power devices, the gate driver that controls the device by a pulse width modulation (PWM) signal is becoming more important The vital function of the gate driver is to provide an isolated gate signal against the reference source voltage that operates at high voltage In addition to this function, their integration with GaN power HFETs is also desirable to achieve smaller system size, lower cost and user-friendliness Although there are several signal isolation techniques for a gate driver such as to use a photo-coupler and wireless pulse transformer [2], these techniques have disadvantages such as large system size and difficulty in integration Other bootstrap or charge pump techniques [3] in high voltage gate drivers (HVIC) have been developed to generate a reference voltage, but the driver can only be used in particular applications such as inverters Meanwhile, we have focused our attention on the recent technology of wireless power transmission using an electromagnetic resonant coupler (EMRC) [4] with an open-ring resonator [5], which is very attractive due to its high efficiency in power transmission and its compactness at high frequency

A DC-isolated gate drive IC with drive-by-microwave technology for power switching devices

A 26 GHz short-range radar (SRR) system has been developed based on a 2.5 Gcps direct sequence spread spectrum (DSSS) technique combined with simple homodyne detection. Separate frequency-triplers have been provided with transmitter (TX) and receiver (RX) chips to cut off the carrier-leakage path from local signal. By using this configuration, carrier-leakage in TX signal can be significantly suppressed falling into the satisfactory range of the UWB regulation. The present radar system achieved the maximum detection range of 14 m with the resolution of 6 cm. TX, RX, and PN generator chipset has been developed using InGaP/GaAs HBT process, where fT/fmax of 65 GHz/ 83 GHz were attained.

A 26GHz Short-Range UWB Vehicular-Radar Using 2.5Gcps Spread Spectrum Modulation

This paper describes an ultracompact GaN 3 × 3 matrix power converter with drive-by-microwave (DBM) technology, which comprises a radio frequency (RF)-triggered GaN-gate injection transistor (GIT) bidirectional power switches integration chip with co-integrated RF rectifiers, novel isolated dividing couplers in a printed circuit board to reduce complicated gate lines, and low-consumption GaN/Si DBM gate driver on a chip that controls nine bi-directional power switches. The proposed 4.0-kW GaN 3 × 3 matrix power converter is extremely compact, measuring only 18 × 25 mm due to the use of GaN-GIT power device integration technology and DBM technology that provides isolated gate signals by microwave wireless power transmission and eliminates the need for photo-couplers and isolated power supplies. The GaN/Si DBM driver realizes low power consumption of only 2.0 W as a result of gate power sharing with three RF oscillators. The sequential switching operation by the fabricated GaN 3 × 3 matrix converter was successfully achieved.

A 3-Phase AC–AC Matrix Converter GaN Chipset With Drive-by-Microwave Technology

In this paper, we describe a GaN 3x3 matrix converter chipset, which are composed of a GaN integrated bidirectional switching chip and a GaN integrated gate drive transmitter chip using 5.0GHz Drive-by-Microwave technology. The extremely compact three phase AC-AC matrix converter such as a 25x18mm2 is realized by these GaN/Si integrated chips and novel isolated dividing couplers, which duplicate the gate signal with different references for dual-gate bidirectional switches and reduce gate lines and gate drive components by half. The proposed GaN 3x3 matrix converter is significantly more compact than the conventional one that requires numerous power switches, flywheel diodes, photo-couplers, isolated power supplies and gate drivers.

30.5 A GaN 3×3 matrix converter chipset with Drive-by-Microwave technologies

The isolated direct gate driver with Drive-by-Microwave technologies can directly drive a power switching device by wireless power transmission of RF modulated signal through the electromagnetic resonant coupler and requires no additional isolated voltage source. In order to improve the performance such as a fall time characteristic and a power consumption of the gate driver, a new direct gate driver using a SPDT switch is proposed, which can effectively switch the inter-channels for the positive and negative voltage outputs. The fabricated GaN single-chip direct gate driver realized 2.0Mbps signal isolation and successfully drove a GaN power switching device with a very fast fall time by the negative voltage output for off-state.

Noboru Negoro

Papers

A DC-isolated gate drive IC with drive-by-microwave technology for power switching devices

A 26GHz Short-Range UWB Vehicular-Radar Using 2.5Gcps Spread Spectrum Modulation

A 3-Phase AC–AC Matrix Converter GaN Chipset With Drive-by-Microwave Technology

30.5 A GaN 3×3 matrix converter chipset with Drive-by-Microwave technologies

A one-chip isolated gate driver with an electromagnetic resonant coupler using a SPDT switch