GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> The evolution of smart power technology and the impact of this technology on electronic systems are reviewed. After providing a definition of smart power technology, the author describes the key technological developments in power semiconductor devices, namely power MOSFETs and IGBTs (insulated-gate bipolar transistors). These developments are the foundation upon which smart power technology rests. Smart power technology requires the marriage of power device technology with CMOS logic and bipolar analog circuits. The technical challenges involved in combining power handling capability with on-chip regulation of overcurrent, overvoltage, and overtemperature conditions are described, together with examples of solutions for telecommunications, motor control, and switch mode power supplies. > <s> BIB001 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> This paper reviews the latest trends in the use of integrated circuits in motor control and the consequences of recent integrated circuit technology developments on the designs of motor control subsystems. Three segments are analyzed in detail: portable equipment, domestic appliances and automotive electronics. In addition, new device packaging concepts for motor driving ICs are described. <s> BIB002 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> 1 BCD Technologies for Smart Power ICs.- 2 Technologies for High Voltage ICs.- 3 Smart Discrete Technologies.- 4 Dielectric Isolation Technologies and Power ICs.- 5 Power Mosfets Driving Circuits and Protection Techniques.- 6 Motion Control.- 7 Switching Regulators.- 8 High Voltage Integrated Circuits for Off-Line Power Applications.- 9 Automotive Electronics.- 10 Audio Amplifiers.- 11 High Complexity Smart Power Devices and Future Developments.- 12 Modeling, Design and Simulation of Power Electronic Devices and Circuits.- 13 Packaging.- 14 Reliability of Smart Power ICs. <s> BIB003 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A high-performance 600 V smart power technology has been developed in which novel lateral double-diffused MOS transistors (LDMOS) are merged with a BiCMOS process flow for the construction of power integrated circuits on bonded silicon-on-insulator (BSOI) substrates. All active and passive device structures have been optimized for fabrication on BSOI layers which are less than 1.5 /spl mu/m-thick, with buried oxide layers in the range of 2.0 to 3.0 /spl mu/m-thick. Complete dielectric isolation processing is straightforward due to the use of a thin SOI active device layer. A dual field plate design of the high-voltage devices results in at least a factor-of-two reduction in specific on-resistance over conventional LDMOS structures for a given breakdown voltage. <s> BIB004 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems. <s> BIB005 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A recessed-gate structure has been studied with a view to realizing normally off operation of high-voltage AlGaN/GaN high-electron mobility transistors (HEMTs) for power electronics applications. The recessed-gate structure is very attractive for realizing normally off high-voltage AlGaN/GaN HEMTs because the gate threshold voltage can be controlled by the etching depth of the recess without significant increase in on-resistance characteristics. With this structure the threshold voltage can be increased with the reduction of two-dimensional electron gas (2DEG) density only under the gate electrode without reduction of 2DEG density in the other channel regions such as the channel between drain and gate. The threshold-voltage increase was experimentally demonstrated. The threshold voltage of fabricated recessed-gate device increased to -0.14 V while the threshold voltage without the recessed-gate structure was about -4 V. The specific on-resistance of the device was maintained as low as 4 m/spl Omega//spl middot/cm/sup 2/ and the breakdown voltage was 435 V. The on-resistance and the breakdown voltage tradeoff characteristics were the same as those of normally on devices. From the viewpoint of device design, the on-resistance for the normally off device was modeled using the relationship between the AlGaN layer thickness under the gate electrode and the 2DEG density. It is found that the MIS gate structure and the recess etching without the offset region between recess edge and gate electrode will further improve the on-resistance. The simulation results show the possibility of the on-resistance below 1 m/spl Omega//spl middot/cm/sup 2/ for normally off AlGaN/GaN HEMTs operating at several hundred volts with threshold voltage up to +1 V. <s> BIB006 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> This paper presents a method with an accurate control of threshold voltages (Vth) of AlGaN/GaN high-electron mobility transistors (HEMTs) using a fluoride-based plasma treatment. Using this method, the Vth of AlGaN/GaN HEMTs can be continuously shifted from -4 V in a conventional depletion-mode (D-mode) AlGaN/GaN HEMT to 0.9 V in an enhancement-mode AlGaN/GaN HEMT. It was found that the plasma-induced damages result in a mobility degradation of two-dimensional electron gas. The damages can be repaired and the mobility can be recovered by a post-gate annealing step at 400 degC. At the same time, the shift in Vth shows a good thermal stability and is not affected by the post-gate annealing. The enhancement-mode HEMTs show a performance (transconductance, cutoff frequencies) comparable to the D-mode HEMTs. Experimental results confirm that the threshold-voltage shift originates from the incorporation of F ions in the AlGaN barrier. In addition, the fluoride-based plasma treatment was also found to be effective in lowering the gate-leakage current, in both forward and reverse bias regions. A physical model of the threshold voltage is proposed to explain the effects of the fluoride-based plasma treatment on AlGaN/GaN HEMTs <s> BIB007 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A lateral field-effect rectifier (L-FER) that can be fabricated with normally-off transistor on the same AlGaN/GaN HEMT with the same fabrication process has been demonstrated. The L-FER exhibits low turn-on voltage, low specific on-resistance and high reverse breakdown. A prototype of switch-mode dc-dc boost converter that features monolithically integrated L-FER and normally-off HEMT is demonstrated for the first time using industry-standard GaNon-Si epitaxial wafers to prove the feasibility of GaN power integrated technology. <s> BIB008 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Wide-bandgap GaN-based semiconductor materials are attracting considerable attention as the preferred material for power electronics applications, owning to their superior properties including high breakdown electric-field, high carrier density, high electron mobility and high saturation velocity. In this paper, the technologies for implementing GaN smart power ICs will be introduced based on the large-size, low-cost and highly scalable GaN-on-Si platform. High-voltage power components (normally-off power transistors and HEMT-compatible rectifiers) and low-voltage periphery devices for digital/analog mixed-signal circuits are successfully integrated with the same fabrication process. In particular, key analog functional blocks such as voltage reference generators and comparators are demonstrated using GaN-based technology for the first time. The optimized voltage reference generator achieved less than 70 ppm/°C drift and can be used as a reference voltage in various biasing and sensing circuits. The temperature-dependent performance of a conventional comparator is characterized and a new temperature-compensated comparator circuit is also demonstrated. The positive limiting level of the temperature-compensated comparator is less than 450 ppm/°C drift compared to 1400 ppm/°C in the conventional comparator <s> BIB009 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> We demonstrate a single-chip switch-mode boost converter that features a monolithically integrated lateral field-effect rectifier (L-FER) and a normally off transistor switch. The circuit was fabricated on a standard AlGaN/GaN HEMT epitaxial wafer grown with GaN-on-Si technology. The fabricated rectifier with a drift length of 15 mum exhibits a breakdown voltage of 470 V, a turn-on voltage of 0.58 V, and a specific on-resistance of 2.04 mOmegaldrcm2. The L-FER exhibits no reverse recovery current associated with the turn-off transient because of its unipolar nature. A prototype of GaN-based boost converter that includes monolithically integrated rectifiers and transistors is demonstrated using conventional GaN-on-Si wafers for the first time to prove the feasibility of the GaN-based power IC technology. <s> BIB010 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> GaN smart power chip technology has been realized on the GaN-on-Si platform, featuring monolithically integrated high-voltage power devices, and low-voltage peripheral devices for mixed-signal functional blocks. In particular, this paper presents the imperative analog functional block - the voltage reference generator for smart power applications with wide-temperature-range stability. These circuits are shown to be capable of proper functions from room temperature (RT) up to 250 °C, featuring a negative reference voltage of -2.21 V at RT, and -2.13 V at 250 °C. The optimized voltage reference generator achieved less than 0.5 mV/°C drift. It can be used to create a reference voltage for various biasing and sensing circuits. <s> BIB011 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> GaN smart power chip technology has been realized using a GaN-on-Si HEMT platform, featuring monolithically integrated high-voltage power devices and low-voltage peripheral devices for mixed-signal functional blocks. In particular, this brief presents the imperative analog functional block-voltage reference generator for smart power applications with wide-temperature-range stability. The circuit is capable of proper functions within a wide temperature range from room temperature up to 250°C , illustrating the unique advantage of the wide-bandgap GaN in high-temperature operation. The voltage reference generator was designed with an AlGaN/GaN HEMT and Schottky diodes, and the devices were operated in the subthreshold regime to obtain low power consumption. The voltage reference generator achieved an average drift of less than 0.5 mV/°C and can be used as a reference voltage in various biasing and sensing circuits. <s> BIB012 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A high-performance bootstrapped comparator operating with a single-polarity power supply is demonstrated for GaN high-temperature electronics applications. The comparator features monolithically integrated enhancement-mode (E-mode) and depletion-mode (D-mode) AlGaN/GaN HEMTs. The tail current source uses an E-mode HEMT, enabling single-polarity power supply. The E-mode input stage could cover a wide voltage comparison range (from 1 to 6 V) while the bootstrapped loads are implemented with D-mode HEMTs. At room temperature, the comparator delivers a voltage gain as high as 79 V/V and a unity-gain bandwidth of 206 MHz. At 250 , a maximum voltage gain of 40 V/V and a unity-gain bandwidth of 84 MHz are obtained. <s> BIB013 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Gallium-nitride power transistor (GaN HEMT) and integrated circuit technologies have matured dramatically over the last few years, and many hundreds of thousands of devices have been manufactured and fielded in applications ranging from pulsed radars and counter-IED jammers to CATV modules and fourth-generation infrastructure base-stations. GaN HEMT devices, exhibiting high power densities coupled with high breakdown voltages, have opened up the possibilities for highly efficient power amplifiers (PAs) exploiting the principles of waveform engineered designs. This paper summarizes the unique advantages of GaN HEMTs compared to other power transistor technologies, with examples of where such features have been exploited. Since RF power densities of GaN HEMTs are many times higher than other technologies, much attention has also been given to thermal management-examples of both commercial “off-the-shelf” packaging as well as custom heat-sinks are described. The very desirable feature of having accurate large-signal models for both discrete transistors and monolithic microwave integrated circuit foundry are emphasized with a number of circuit design examples. GaN HEMT technology has been a major enabler for both very broadband high-PAs and very high-efficiency designs. This paper describes examples of broadband amplifiers, as well as several of the main areas of high-efficiency amplifier design-notably Class-D, Class-E, Class-F, and Class-J approaches, Doherty PAs, envelope-tracking techniques, and Chireix outphasing. <s> BIB014 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> In this paper, we present a novel GaN-based normally-off transistor with an integrated Si Schottky barrier diode (SBD) for low voltage DC-DC converters. The integrated SBD is formed by the Si substrate for the epitaxial growth of AlGaN/GaN hetero-structure, which is connected to the normally-off GaN Gate Injection Transistor (GIT) over it with via-holes. The diode can flow the reverse current in the conversion operation with lower forward voltage than that of the lateral GaN transistor enabling lower operating loss. A DC-DC converter from 12V down to 1.3V using the integrated devices with the reduced gate length down to 0.5μm exhibits a high peak efficiency of 89% at 2MHz demonstrating the promising potential of GaN devices for the application. <s> BIB015 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Commercial RF MMIC fabrication process technologies were investigated for fabrication of integrated switching power converters. Pulsed IV characterization of GaN FETs revealed ON resistance dependence on off state bias, and current collapse at high temperatures. The degradation in ON resistance and current collapse can severely impact the efficiency of switching circuits fabricated in these processes. <s> BIB016 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> We demonstrate high-voltage depletion-mode and enhancement-mode (E-mode) AlGaN/GaN high-electron-mobility transistors (HEMTs) on a GaN-on-silicon-on-insulator (SOI) platform. The GaN-on-SOI wafer features GaN epilayers grown by metal-organic chemical vapor deposition on a p-type (111) Si SOI substrate with a p-type (100) Si handle wafer. Micro-Raman spectroscopy significantly reveals reduced stress in the GaN epilayers, which is a result expected from the compliant SOI substrate. E-mode HEMTs fabricated by fluorine plasma implantation technique deliver high on/off current ratio (108-109), large breakdown voltage (1471 V with floating substrate), and low on-resistance (3.92 mΩ·cm2). <s> BIB017 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A novel ultra-low phase noise and high power integrated oscillator is presented in this letter. The proposed oscillator, based on GaN-on-SiC high electron mobility transistor (HEMT) with 0.25 μm gate length and 800 μm gate width, delivers 21 dBm output power when biased at VGS=-3 V and VDD = 28 V. Phase noise was measured to be -112 dBc/Hz at 100 kHz offset and -135 dBc/Hz at 1 MHz offset from 7.9 GHz carrier, respectively. To the best of our knowledge, it achieves the lowest phase noise compared to other GaN HEMT based integrated oscillators. It is also comparable in performance to the state-of-the-art ultra-low phase noise oscillators designed in InGaP technology, while delivering more than 10 times higher output power. In addition, this oscillator also exhibits a minimum second harmonic suppression of 28.65 dBc and more than 60 dBc third harmonic suppression. The chip size is 1.1×0.6 mm2. The results show that the proposed oscillator has the potential to be used for both low phase noise and high power microwave source applications. <s> BIB018 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> In this paper, we report state-of-the-art high frequency performance of a W-band voltage-controlled oscillator (VCO) MMIC realized in a 0.1 μm AlGaN/GaN HEMT technology. The oscillation frequency of the VCO can be tuned between 85.6 and 92.7 GHz, which is a relative tuning bandwidth of 8%. The achieved maximum output power is as high as 10.6 dBm. The phase noise of the VCO varies from -80.2 to -90.2 dBc/Hz at 1 MHz offset from the carrier over the tuning voltage range. <s> BIB019 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> 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. <s> BIB020 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> In this paper, we present a novel compact DC-DC converter IC in which normally-off GaN-GITs (Gate Injection Transistors) and gate drivers are integrated into one chip. The DC-DC converter IC can achieve higher efficiency and smaller chip size by reducing parasitic inductances between switching power devices and gate drivers. The gate driver, having a DCFL (Direct Coupled FET Logic) with a buffer amplifier which is consisted of a GaN-HFET (Hetero-junction FET) and GaN-GITs can operate with higher speed and lower power consumption. The fabricated DC-DC converter IC exhibits a peak efficiency as high as 86.6% at 2MHz for the 12V-1.8V conversion. <s> BIB021 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> With global drivers such as better energy consumption, energy efficiency and reduction of greenhouse gases, CO2 emission reduction has become key in every layer of the value chain. Power Electronics has definitely a role to play in these thrilling challenges. From converters down to compound semiconductors, innovation is leading to breakthrough technologies. Wide BandGap, Power Module Packaging, growth of Electric Vehicle market will game changed the overall power electronic industry and supply chain. In this presentation we will review power electronics trends, from technologies to markets. <s> BIB022 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> AlGaN/GaN power HEMT combined with partial AlGaN barrier recess and multiple CHF 3 based fluorine plasma treatments onto ALD deposited Al 2 O 3 gate dielectrics is able to bring a high gate threshold voltage (V TH ) for the enhancement mode operations without much degradation on the maximum drain saturation current (I DMAX ). This work reports integration of both the enhancement and depletion (E-D) modes AlGaN/GaN MIS-HEMTs to construct a monolithic inverter. Experimental data show that the proposed power inverter provides large noise margin allowances of 4.9V and 3.2V, large output swing of 9.66V and satisfactory propagation switching delay time of 35ns. The configuration is found to be suitable for GaN power integrated circuits. <s> BIB023 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> We report the first gallium nitride (GaN)-based pulse width modulation (PWM) integrated circuit (IC) featuring monolithically integrated enhancement- and depletion-mode high electron mobility transistors and lateral field-effect rectifiers on the GaN smart power technology platform. The PWM IC is able to generate 1-MHz PWM signal with its duty cycle modulated effectively by a reference voltage ( $V_{c})$ over a wide range with good linearity. It features a 5 V supply voltage and is composed of a sawtooth generator and a comparator, both of which can be operated at 1 MHz and exhibit proper functionality over a wide temperature range (from 25 °C to 250 °C). This circuit demonstration further proves the feasibility of an all-GaN solution that features monolithically integrated peripheral gate control circuits and power switches for GaN power converters. An all-GaN solution would lead to a compact system with improved efficiency and enhanced reliability. <s> BIB024 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> We provide an overview of key challenges and technical breakthroughs that led to development of highly scaled GaN HEMT's having ft > 400 GHz and fmax > 550 GHz and the corresponding IC process. These highly scaled GaN devices have 5 times higher breakdown voltage than transistors with similar high frequency RF power gain in other semiconductor systems (Si, SiGe, InP, GaAs). We also report performance of the first generation of MMIC power amplifiers (PAs) that utilize these highly scaled devices. The power added efficiency (PAE) of 59% measured at a frequency of 32 GHz, bias of 3 V and output power of 24.3 dBm of the first generation Ka-band MMIC PAs that were built using these highly scaled GaN devices, represent a significant improvement in PAE over values reported for other semiconductor technologies at this frequency band as well as for Ka-band MMICs built in lower frequency GaN nodes. Presented data suggest that highly scaled GaN transistors are excellent candidates for MMIC PAs for next generation 28 GHz, 39 GHz, and higher frequency 5G mobile bands, because they would greatly extend battery lifetime in mobile handsets, due to their superior PAE compared to competing semiconductor technologies. <s> BIB025 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> This paper presents the design and measurement of a proof-of-concept fully monolithically integrated DC-DC converter operating at 4.6 GHz. The converter is designed in Qorvo's 0.15 µm GaN on SiC process and has a total area of 2.5mm × 3.8 mm. The distributed class-E2 converter does not use any external inductors or other lumped elements. The maximum efficiency achieved by the converter is 48% at 0.6W output power. The converter can also operate in self-synchronous mode without rectifier gate drive, albeit with a drop in performance. <s> BIB026 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Due to its remarkably high Johnson figure of merit, gallium nitride (GaN) has become the material of choice for applications requiring high output power at high frequencies. In this paper, we have reviewed high-speed switching work to date and we demonstrate a 28 V, 865-MHz switching speed step-down converter that can be applied to envelope tracking (ET). We report a GaN monolithic microwave integrated circuit technology utilized to fabricate a gate driver IC at a switching speed >1 GHz with 100 V breakdown GaN power switch. The on-chip integration of the power switch and gate driver allows in-circuit characterization of the power switch switching speed. Using the integrated gate driver and switch, we report a slew rate of the power switch of 152 V/ns at 50 V, which enables a down converter IC capable of ET with over 50-MHz tracking bandwidth. This paper shows the first demonstration of a GaN low-side gate driver capable of >1-GHz switching, monolithic integration with a 0.15- $\mu \text{m}$ T-gate suitable for up to Ka-band operation, and a >100 V breakdown voltage power switch on the same chip. <s> BIB027 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Integration is a key step in utilizing advances in GaN technologies and enabling efficient switched-mode power conversion at very high frequencies (VHF). This paper addresses design and implementation of monolithic GaN half-bridge power stages with integrated gate drivers optimized for pulsewidth-modulated (PWM) dc–dc converters operating at 100 MHz switching frequency. Three gate-driver circuit topologies are considered for integration with half-bridge power stages in a 0.15- $\mu$ m depletion-mode GaN-on-SiC process: an active pull-up driver, a bootstrapped driver, and a novel modified active pull-up driver. An analytical loss model is developed and used to optimize the monolithic GaN chips, which are then used to construct 20 V, 5 W, 100 MHz synchronous buck converter prototypes. With the bootstrapped and the modified pull-up gate-driver circuits, power stage efficiencies above 91% and total efficiencies close to 88% are demonstrated. The modified active pull-up driver, which offers 80% reduction in the driver area, is found to be the best-performing approach in the depletion-mode GaN process. These results demonstrate feasibility of high-efficiency VHF PWM dc–dc converters based on high levels of integration in GaN processes. <s> BIB028 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic $R_{\mathrm {{ds}},\mathrm {{on}}}$ , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale. <s> BIB029 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> 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. <s> BIB030 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> Several new technologies for GaN high frequency devices and GaN power devices are reviewed. Newly developed GaN devices have a superior performance over conventional Si ones in view of lowering the energy loss and reducing the system size. Normally-off GaN HFETs, GaN monolithic IC, GaN isolated gate driver ICs, and GaN 3×3 matrix converter IC are demonstrated. We believe these technologies will open “Green” power electronics in the future. <s> BIB031 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> This paper reports the design, development and performance of a 28 GHz 480 elements digital Active Antenna System (AAS) prototype for 5G long-range applications. AAS accommodates 32 channels of 0.15 um GaN HEMT power amplifier chains. The antenna array prototype consists of full digitally controlled 32 streams of 15 elements sub-arrays. They can deliver a total conductive power of 41 dBm and Average Effective Isotropically Radiated Power (EIRP) of 68 dBm for the macro-cell coverage at 28 GHz. The prototype also features newly proposed high density heat spreading structure dissipating around 450 W in an 11 liter compact enclosure. The paper proposes and demonstrates one of direction of the high power GaN HEMT application to the millimeter-wave 5G long-range base stations. <s> BIB032 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> In order to examine the feasibility of full wide-bandgap GaN-based converters in aerospace power conversion applications, this paper proposes a monolithic DC–DC buck converter design with integrated high-side gate driver, over-current protection, and pulse-width-modulation feedback control circuits based on full AlGaN/GaN MIS-HEMT configuration. After model calibration of the DC and transient behaviors with fabricated normally-ON and normally-OFF AlGaN/GaN MIS-HEMT devices, the DC–DC buck converter is simulated. The circuit converts the input 100 V down to an adjustable range at 1 MHz switching frequency. The over-current protection function can properly protect the converter at a preset over-current threshold. The converter can respond to the load current and line input voltage fluctuations due to the integrated feedback control. These results illustrate the performance of proposed all-GaN DC–DC power converter design. <s> BIB033 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> 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. <s> BIB034 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> GaN-based digital integrated circuits (ICs) are realized on a 6-inch GaN-on-Si power high-electron-mobility transistor (HEMT) platform by monolithic integration of enhancement/depletion-mode HEMTs using a 0.5- $\mu \text{m}$ gate technology. A direct-coupled FET logic inverter and a 101-stage ring oscillator are fabricated and characterized. The inverter exhibits a large input voltage swing, wide noise margin, and high temperature stability, while the ring oscillator features a small propagation delay of 0.1 ns/stage under a supply voltage of 4 V. These digital ICs can operate properly up to at least 200 °C and show great potential for GaN smart power IC applications. <s> BIB035 </s> GaN Power Integration for High Frequency and High Efficiency Power Applications: A Review <s> I. INTRODUCTION <s> A fully-integrated data transmission system based on gallium nitride (GaN) high-electron-mobility transistor (HEMT) devices is proposed. This system targets high-temperature (HT) applications, especially those involving pressure and temperature sensors for aerospace in which the environmental temperature exceeds 350 °C. The presented system includes a front-end amplifying the sensed signal (gain of 50 V/V), followed by a novel analog-to-digital converter driving a modulator exploiting the load-shift keying technique. An oscillation frequency of 1.5 MHz is used to ensure a robust wireless transmission through metallic-based barriers. To retrieve the data, a new demodulator architecture based on digital circuits is proposed. A 1 V amplitude difference can be detected between a high-amplitude (data-on) and a low-amplitude (data-off) of the received modulated signal. Two high-voltage supply levels (+14 V and −14 V) are required to operate the circuits. The layout of the proposed system was completed in a chip occupying 10.8 mm2. The HT characterization and modeling of integrated GaN devices and passive components are performed to ensure the reliability of simulation results. The performance of the various proposed building blocks, as well as the whole system, have been validated by simulation over the projected wide operating temperature range (25–350 °C). <s> BIB036
In the view of minimizing power consumption and heat dissipation during signal or energy conversions, high frequency and high efficiency are most attractive among the premier interests on the power IC designers' checklist BIB022 , BIB002 . The volume of magnetic energy storage components and the system conversion loss can be largely reduced under higher operation frequency BIB003 . Moreover, transistors, diodes and passive components can be monolithically integrated to eliminate the parasitic inductance brought by bonding wires to further push the frequency and efficiency, which leads to the wide introduction of power integrated circuits BIB001 , BIB004 . Other than the development of power IC design techniques, the continuous performance evolution of power integrated devices has accelerated the adoption of novel materials BIB030 , BIB011 . Compared with Si, GaN material possesses over ∼3.1 times of energy bandgap, ∼2.7 times of electron saturation velocity and ∼11.6 times of critical electric field, which The associate editor coordinating the review of this manuscript and approving it for publication was Ivona Mitrovic . makes GaN suitable for RF and power conversion applications BIB005 . Especially the GaN High Electron Mobility Transistors (HEMTs) exhibit a 2-Dimentional Electron Gas (2DEG) channel and well fit the lateral integration  , BIB009 , which is a promising road to fully exploit the merits of GaN material. The Monolithic Microwave Integrated Circuit (MMIC) was proposed in the GaAs-age with the first MMIC in 1975  and now is still the mainstream process for GaNbased RF and microwave applications BIB016 , BIB031 . Based on single-chip air-bridge integration of HEMTs, thin film or epitaxy resistors, and metal-insulator-metal capacitors, MMIC process has supported the high frequency microwave electronics from MHz to GHz ranges BIB014 , BIB025 . The critical dimensions of GaN MMIC process has been reduced from several microns to sub-micron scale of 0.5 µm BIB036 , 0.25 µm BIB018 , 0.15 µm BIB032 , 0.1 µm BIB019 , 0.04 µm and 0.02 µm BIB025 . Commercial GaN HEMT MMIC platforms include BAE Systems, Fujitsu, Fraunhofer, HRL, MACOM, Northrop Grumman Aerospace Systems and Electronic Systems, NXP, Oki, Qorvo, Raytheon, Wolfspeed and so on, together with many other foundries listing GaN on their VOLUME 8, 2020 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see http://creativecommons.org/licenses/by/4.0/ roadmaps. The highly scaled GaN HEMTs have formed excellent MMIC power amplifiers for 5G mobile bands with superior power added efficiency (PAE) performance. Besides the RF and microwave applications, MMIC process can also play an important role in power conversion applications BIB026 -  . Ultra-high-frequency (UHF) DC-DC converter for on-chip power supply in Envelope Tracking (ET) application is presented at 865 MHz BIB027 . A buck converter switching at 100 MHz can obtain 90 % efficiency at 9 W output BIB028 . Other works on resonant DC-DC converters are demonstrated at approximately 1 GHz  . However, due to the relative low length of drift region in highly scaled GaN HEMTs in MMIC platforms, the state-of-the-art breakdown voltage is mostly below 150 V. Also the threshold voltage of HEMTs is negative, which is not fault-safe and requires specially designed gate driver. These conditions restrain GaN MMIC processes from realizing high voltage and high power DC-DC converters BIB033 . GaN power HEMTs or Metal-Insulator-Semiconductor (MIS) HEMTs with normally-OFF operation are introduced by means of gate recess BIB006 , fluorine-ion implantation BIB007 , p-type cap layer  or cascode structure BIB034 . The GaN normally-OFF power devices has ushered a new age of high-frequency and high-efficiency power conversion. Major power semiconductor companies have launched their GaN product lines, such as Cree, Infineon, Panasonic, ON-semi, Texas Instruments and TSMC, while other start-up companies are growing to key players including Efficient Power Conversion (EPC), GaN System, Navitas, Transphorm, VisIC and Wolfspeed. With the increasing availability of commercial discrete devices, the constructed power converter with GaN normally-OFF transistors have surpassed the Si-based counterparts in both output efficiency and operation frequency. It has realized over 95 % efficiency at over 1 MHz and output power over 1 kW BIB020 , BIB029 . In order to minimize the converter volume for high frequency and high efficiency power conversion, normally-OFF power integration platforms are proposed BIB030 ,  , BIB009 , BIB035 - BIB017 . Integration schemes in power converters start from normally-OFF HEMTs with diodes for boost converters using fluorine-ion implantation technique in 2008 BIB010 , BIB008 and p-type cap-layer Gate-Injection-Transistor technique in 2012 BIB015 . Later integrated half-bridges, full-bridges are realized with pre-gate driver to reduce the inductance of gate drive loop and a 12 V-1.8 V converter exhibits peak efficiency of 86.6 % at 2 MHz BIB021 . In the meantime, functional circuits such as inverter BIB023 , comparator BIB013 , voltage reference generator BIB012 and pulse-width-modulation circuit BIB024 are fabricated and have successfully demonstrated the analog functions of GaN integrated circuits. The tide of high-speed GaN revolution keeps rising in industries. The consumer electronics can benefit in power density, charging speed and cost reduction with highfrequency and high-efficiency GaN power integrated converters. Firstly Navitas and Dialog have launched their System on Chip (SoC) GaN power ICs NV6115 and DA8801, respectively. In the meantime, EPC, Infineon, Tagore Technology and Texas Instruments choose the System in Package (SiP) road. The close proximity of devices and components can greatly reduce parasitic inductance to boost the switching speed. Based on low-voltage transistors, functional subcircuits including gate driver, control and feedback circuits can be integrated as well. In this paper, the GaN power integration for high frequency and high efficiency power applications is systematically reviewed. In the view of power ICs, the structure and property of GaN power devices are firstly discussed in section II, including the reasons why lateral integration is a choice. In section III the GaN MMIC processes are briefly presented in terms of critical dimensions and IC performance. The GaN smart power IC platforms are discussed in section IV with the development of device technology. Section V includes novel integration platforms and technologies to shed some light on future direction of the GaN integration road. Finally, Section VI summaries this review.