SiC devices are promising for outperforming Si counterparts in high-frequency applications due to its superior material properties. Conventional wirebonded packaging scheme has been one of the most preferred package structures for power modules. However, the technique limits the performance of a SiC power module due to parasitic inductance and heat dissipation issues that are inherent with aluminum wires. In this article, low parasitic inductance and high-efficient cooling interconnection techniques for Si power modules, which are the foundation of packaging methods of SiC ones, are reviewed first. Then, attempts on developing packaging techniques for SiC power modules are thoroughly overviewed. Finally, scientific challenges in the packaging of SiC power module are summarized.

/pdf/review-of-packaging-schemes-for-power-module-1bxfgdpj20.pdf

Review of Packaging Schemes for Power Module

We present a GaN monolithic inverter IC on Si substrate and successful motor-drive by it for the first time. Taking advantages of the bi-directional operation free from the forward voltage off-set [1], the inverter can be operated just by the integrated six GaN-based normally-off gate injection transistors (GITs) without any external fast recovery diodes (FRDs) to flow the fly-wheel current. The IC enables the efficiency as high as 93% at low power operation where so far that of conventional Si-based inverters has remained lower value owing to the forward voltage off-set. The key processing technology is the newly introduced planar isolation using Fe ion implantation which fully isolates the GaN-based lateral devices each other.

GaN Monolithic Inverter IC Using Normally-off Gate Injection Transistors

Terahertz (THz) links will play a major role in high data rate communication over a distance of few meters. In order to achieve this task, antenna designs with high gain and wideband characteristics will spearhead these links. In this contribution, we present different antenna designs that offer characteristics better suited to THz communication over short distances. Firstly, a single-element antenna having a dipole and reflector is designed to operate at 300 GHz, which is considered as a sub-terahertz band. That antenna achieves a wide impedance bandwidth of 38.6% from 294 GHz to 410 GHz with a gain of 5.14 dBi. Secondly, two designs based on the same dipole structure but with added directors are introduced to increase the gain while maintaining almost the same bandwidth. The gains achieved are 8.01 dBi and 9.6 dBi, respectively. Finally, an array of elements is used to achieve the highest possible gain of 13.6 dBi with good efficiency about 89% and with limited director elements for a planar compact structure to state-of-the-art literature. All the results achieved make the proposed designs viable candidates for high-speed and short-distance wireless communication systems.

Sub-THz Antenna for High-Speed Wireless Communication Systems

This study presents monolithically integrated power circuits, fabricated in a high-voltage GaN-on-Si heterojunction technology. Different advanced concepts are presented and compared with solutions found in the literature. High switching transition slew rates are demonstrated by means of a monolithic power circuit with integrated gate driver. A highly linear temperature sensor is integrated in a GaN-high-electron-mobility transistor (HEMT) power device for the 600 V class and on-state resistance of 53 mΩ. An area-efficient HEMT structure with integrated freewheeling diodes is presented. This structure is applied in a monolithic multilevel converter chip, as well as in a 600 V class half-bridge chip. The multilevel chip is integrated by an advanced printed circuit board embedding technology and tested in inverter operation with a mains voltage output of 120 V
 RMS
. The performance of the half-bridge is demonstrated in a synchronous buck converter operation from 400 to 200 V and with a switching frequency of 3 MHz.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2017.0397

Monolithically integrated power circuits in high-voltage GaN-on-Si heterojunction technology

Gallium nitride (GaN) transistors are being employed in an increasing number of applications thanks to their excellent performance and competitive price. Yet, GaN diodes are not commercially available, and little is known about their performance and potential impact on power circuit design. In this article, we demonstrate scaled-up GaN-on-Si Tri-Anode Schottky barrier diodes (SBDs), whose excellent dc and switching performance are compared to commercial Si fast-recovery diodes and SiC SBDs. Moreover, the advantageous lateral GaN-on-Si architecture enables the integration of several devices on the same chip, paving the way for power integrated circuits (ICs). This is demonstrated by realizing a diode-multiplier IC, which includes up to eight monolithically integrated SBDs on the same chip. The IC was integrated on a dc–dc magnetic-less boost converter able to operate at a frequency of 1 MHz. The IC performance and footprint are compared to the same circuit realized with discrete Si and SiC vertical devices, showing the potential of GaN power ICs for efficient and compact power converters.

/pdf/ultra-compact-high-frequency-power-integrated-circuits-based-1thwuw9b5t.pdf

Ultra-compact, High-Frequency Power Integrated Circuits Based on GaN-on-Si Schottky Barrier Diodes

A low-inductive half-bridge and gate driver package with on-package gate and dc-link capacitors is realized by printed circuit board (PCB) embedding of two GaN-on-Si ICs. While monolithic half-bridge and driver integration reduces on-chip parasitics, it does not solve the interconnection challenge to external capacitors. This letter solves this issue through advantageous combination of PCB embedding and monolithic circuit integration. This letter uses GaN-on-Si power circuits with integrated gate drivers, freewheeling diodes, and temperature and current sensors. GaN ICs are fabricated with thick copper on both sides, which makes them applicable to commercial PCB-embedding technologies. Thermal aspects are discussed and electromagnetic simulations used to compare the PCB-embedded package to a bond wire based package. A PCB-embedded dc–dc converter is operated up to 350 V and 450 W with up to 98.7% efficiency. 380 V hard-switching transitions show below 8% over- and undershoot despite over 120 V/ns slew rates. Parallel platelike placement of silicon flip-chip capacitors above the gate driver final stage transistors and separated only by a thin PCB layer increased the gate-loop parasitic inductance by only 40 pH.

/pdf/pcb-embedded-gan-on-si-half-bridge-and-driver-ics-with-on-2rktdq3glx.pdf

PCB-Embedded GaN-on-Si Half-Bridge and Driver ICs With On-Package Gate and DC-Link Capacitors

This work presents a high-voltage GaN-based power HEMT with a highly-linear, monolithically-integrated temperature sensor. The principle is shown and compared to other concepts. The sensor is fabricated by using a interconnect metallization without additional process steps. The performance of the sensor as well as of the power device is characterized. The 600 V power device achieves an on-state resistance of RON = 55 mO at a corresponding drain current ID = 30 A and an advanced dynamic performance with a low gate charge of 20 nC.

Linear temperature sensors in high-voltage GaN-HEMT power devices

In this paper, a broadband Sequential Power Amplifier (SPA) is designed and realized for the use in an active MIMO antenna around 3.5 GHz. For that purpose, specifications for the individual components are derived to yield optimum performance of the complete SPA when amplifying a mobile communication signal. In order to meet the size requirements of an active antenna, amplifier modules that include all necessary transformation and stabilization networks inside the package are developed. The SPA achieves a bandwidth of more than 1 GHz (RBW of 28%) and shows a peak drain efficiency of 47% in 8 dB backoff at 3.5 GHz. To transmit a complex signal such as QAM using the SPA, its two inputs have to be driven according to the system's characteristic curve. For the first time, modified constellation diagrams for each input have been derived to transmit a 16-QAM-modulated test signal with 10 MBaud at 3.2 GHz. For the amplification of this signal, the system shows an increase in drain efficiency of 10 %-points compared to a conventional class-B PA.

A sequential power amplifier at 3.5 GHz for 5G applications

This paper investigates a printed circuit board (PCB)-embedding technology as packaging technology for 600 V class GaN-on-Si power devices and power integrated circuits (ICs). The electrical and thermal characteristics of PCB-embedding are investigated and compared to conventional assemblies based on wire-bonding and soldering.

PCB-Embedding for GaN-on-Si Power Devices and ICs

A lateral GaN-on-Si power IC is presented, which realizes the core functionality for power converters on-chip. Monolithic integration enhances the functionality of a 600 V, 85mW power transistor by an intrinsic freewheeling diode, gate-driver, current shunt and an isolated temperature sensor. An integrated auxiliary transistor and a diode realize a single-input pre-driver, a current-mirror sensor or a voltage clamp for on-resistance measurement. Gate driver losses were measured up to 70 MHz. A 350V hard-switching half-bridge shows 98.8% efficiency at 600W and 65 kHz. Continuous 40MHz resonant-switching at 200V and 6A triangular peak current was achieved, operating the half-bridge at 50% duty-cycle with a 75 nH air-core inductor. The work demonstrates significant functionality enhancement of large-area GaN power transistors by monolithic integration of additional circuitry at low additional cost and chip area.

Dirk Meder

Papers

PCB-Embedded GaN-on-Si Half-Bridge and Driver ICs With On-Package Gate and DC-Link Capacitors

Linear temperature sensors in high-voltage GaN-HEMT power devices

A sequential power amplifier at 3.5 GHz for 5G applications

PCB-Embedding for GaN-on-Si Power Devices and ICs

A 600V GaN-on-Si Power IC with Integrated Gate Driver, Freewheeling Diode, Temperature and Current Sensors and Auxiliary Devices