Gallium Nitride Technology Research Articles

GaN Technology for Power Electronic Applications: A Review

Power semiconductor devices based on silicon (Si) are quickly approaching their limits, set by fundamental material properties. In order to address these limitations, new materials for use in devices must be investigated. Wide bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN) have suitable properties for power electronic applications; however, fabrication of practical devices from these materials may be challenging. SiC technology has matured to point of commercialized devices, whereas GaN requires further research to realize full material potential. This review covers fundamental material properties of GaN as they relate to Si and SiC. This is followed by a discussion of the contemporary issues involved with bulk GaN substrates and their fabrication and a brief overview of how devices are fabricated, both on native GaN substrate material and non-native substrate material. An overview of current device structures, which are being analyzed for use in power switching applications, is then provided; both vertical and lateral device structures are considered. Finally, a brief discussion of prototypes currently employing GaN devices is given.

Wave approach for noise modeling of gallium nitride high electron‐mobility transistors

AbstractThe wave approach has appeared as a very efficient tool for modeling as well as for measurements of noise parameters of microwave transistors. Having in mind the attractiveness of transistors in gallium nitride technology in modern communication systems, where it is very important to keep the noise on a low level and, thus, to have accurate transistor noise models, in this paper, the wave approach is applied for the noise modeling of high electron‐mobility transistor in gallium nitride technology. The noise wave representation of the transistor intrinsic circuit noise is used, where the noise wave parameters are modeled by exploiting the artificial neural networks. The modeling results, compared with the measured data and with those obtained by the conventional noise equivalent circuit model, provide a verification of the developed model accuracy. Copyright © 2015 John Wiley & Sons, Ltd.

Future Power Electronics with GaN and Diamond

Current trends in power conversion demands systems with more efficiency, higher temperatures of operation and higher power density. Switches, an integral part of every power converter, directly impact the efficacy of the converter, and indirectly its cost. Widebandgap semiconductors like Silicon Carbide (SiC) and Gallium Nitride (GaN) have shown promising performance owing to their superior material quality (compared to Silicon (Si)) that make them the leading materials for next generation power electronics. While SiC and GaN are making impressive progress wider bandgap semiconductors like Aluminum Nitride and Diamond are attracting research interest. This presentation will focus on a developing technology, the vertical GaN technology and its current challenges, and elucidate some recent developments on an emergent one - diamond. Lateral GaN based HEMTs [1] have been designed into power converters successfully that allowed us to study the outcomes at all levels, all the way up to the system. The two important factors that benefited power converters due to the inclusion of a GaN-switch are 1) higher frequency of operation 2) higher temperature of operation, compared to what Si can offer as it reaches its material’s limit. High frequency operation leads to the reduction in electrical form-factor due to reduced size of passive components (capacitors and inductors). Higher temperature of operation allows reduction of cooling accessories hence reducing the mechanical form factor. Higher power (>20KW, although the limits are yet to be determined) applications require vertical device design to maximize the power density. Vertical topology allows higher On-state currents and off-state voltages over a smaller chip area, where the lateral design become unattractive in both cost and performance due to large chip area. Our recent understanding of vertical GaN devices along with the cost of producing bulk GaN substrates portrays a sustainable solution exists for the high power market. Early results from CAVETs [1] have established the fact that bulk GaN devices offer breakdown electric field almost 3 times higher compared to lateral HEMTs. CAVETs have also demonstrated dispersion less output current without the need of complex field plate structures (an integral part of the lateral HEMT design). Our recent research has identified vertical device designs that warranties single chip normally off devices, which will further improve switching performance by eliminating bond wire and PCB trace related inductances. GaN substrates with defect densities lower that 104cm-2 and allowing electron mobility >1100cm2V-1s-1 [2] and recent reports on successful activation of [Mg]-implantated GaN [3] create a very encouraging picture for bulk GaN based power devices. Energy bandgap above 3.4eV is very attractive to continue the roadmap of power electronics towards higher power application (3kV and up), with an increasing power density. With a bandgap of 5.5eV, a critical electric field over 10 MV/cm, and thermal conductivity superior to Si, SiC and GaN, diamond offers the most appropriate combination to serve very high voltage power electronics. One of our recent research achievement demonstrated excellent contacts to n-type diamond, which has been challenging due to very low work function of diamond. Phosphorous doped diamond achieved by Koeck et al. [4] on homoepitaxial diamond substrates led to excellent ohmic contacts to n-type diamond. Applying the novel contact technology on a homoepitaxialy grown p (bottom)-i-n(top) structure, diode operation was achieved with reverse blocking over 150V held over a 1μm thick i-layer. The forward current density was >500A/cm2 around 4V. These early results obtained in diamond clearly show an extremely promising path beyond GaN and SiC. Reference: [1] S.Chowdhury and U.K Mishra, IEEE Transaction on Electron Devices, 60 3060(2013) [2] P Kruszewski et al. The International Workshop on Nitride Semiconductor (2014) [3] T. J. Anderson et al, Electronics Letts. , 50, 197(2014) [4] F.A.M. Koeck et al, Diamond Relat. Mater. 18, 789(2009) Figure 1

(Invited) Low Loss Power Conversion with Gallium Nitride Based Devices

Saving energy by reducing losses in power conversion effectively adds to the energy resources. Recent progress made in Gallium nitride (GaN) technology has opened up new possibilities where the converter losses and size can be reduced significantly, reducing the converter footprint and potentially its cost. GaN offers power electronic devices in two flavors, Lateral and Vertical. Lateral GaN technology in the form of HEMTs is now fairly matured and has been adopted by several industries to design into medium (1kW-20kW) power conversion applications. The benefits as evidenced by reduction in size of passive components and heat sinks are exciting and cost effective. Vertical GaN technology, currently under development, has the potential to serve the higher power (>20kW) conversion applications. The availability of high quality freestanding bulk GaN material initiated by the lighting market has enabled vertical power device to make substantial progress creating new prospects for GaN in power electronics.

Wide-Bandgap-Based Power Devices: Reshaping the power electronics landscape

For the last few years, the virtues of power devices based on gallium nitride (GaN) and silicon carbide (SiC) technologies have been well promoted. Now, with the availability of qualified devices from multiple suppliers and falling prices due to the rise in production and the use of larger substrates, more designers are adopting widebandgap (WBG)-based power devices in their new designs to get to the next level of performance, while others are looking to replace the maturing silicon (Si) with more robust emerging technologies.

GaN HEMT noise modeling based on 50‐Ω noise factor

ABSTRACTThe extraction of a high‐frequency ivalent circuit model plays a fundamental role for the development of any emerging transistor technology. Indeed, an equivalent circuit can provide a valuable support for microwave engineers to ensure a fast and reliable optimization of both device fabrication and circuit design. As far as gallium nitride (GaN) HEMTs are concerned, research efforts have been mostly focused on determining equivalent circuits able to reproduce their large‐signal behavior. Nevertheless, an increasing amount of interest is also being devoted to noise equivalent circuits, due to the interesting GaN technology noise performance. Within this context, the purpose of the present paper is to extract and fully validate an accurate noise model for GaN HEMTs based on a simple, fast, and reliable extraction procedure. The noise model is obtained by assigning an equivalent noise temperature to each resistor of the small‐signal equivalent circuit. The accuracy of the extracted noise model is confirmed by the good agreement between measured and simulated high‐frequency noise parameters. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:937–942, 2015

Elastic Reactance [Microwave Bytes

I suppose it could be regarded as appropriate, given nearly a three-year hiatus, to survey the microwave scene with my ever-more jaundiced eye. I do so, however, with brevity and the consumption of some humble pie as some (not all) of my former targets are alive, well, and going strong. One such, I have to admit, is gallium nitride (GaN) technology, which appears to be triumphing against the odds of cost and becoming the default option for gigahertz power amplifier (PA) designers. So be it; GaN certainly makes radio-frequency PAs (RFPAs) easier to design, although this respite will no doubt be short lived as the specifications adapt to keep us in the forefront of difficulty and on the edge of impossibility. Such is life, but I believe it is still a silicon world, as dramatically shown by the domination of silicon and complementary metal-oxide-semiconductor technology in the millimetric zone. If we can make complete transceivers, not to mention multi watt PAs, with decent efficiency at 100 GHz, a passing observer might question the need for the exotic compound semiconductors that still dominate the world above 1 GHz. Time will tell.

Multispectrum Signal Transmitters: Advances in Broadband High-Efficiency Power Amplifiers for Carrier Aggregated Signals

The growing demand for broadband mobile access drives the deployment of sophisticated and increasingly spectrum-efficient modulation techniques and access technologies resulting in communication signals with highly varying envelopes and increasing peakto-average power ratios (PAPRs). These communication signals call for advanced transmitter architectures and design techniques. This is particularly the case for the constituent radio frequency (RF) power amplifiers (PAs), which are required to amplify communication signals efficiently while maintaining signal quality and minimizing out-of-band emissions in adjacent channels. The Doherty [1] technique has been successfully applied to develop highly efficient solid-state PAs for wireless communication applications. Benefiting from recent advancements in laterally diffused metal oxide semiconductors (LDMOSs), and taking advantage of the advent of gallium nitride (GaN) technology, Doherty PA (DPA) demonstrators with average drain efficiencies approaching 50% were reported in [2]-[4]. Unfortunately, the underlying narrow bandwidth of these demonstrators currently restricts their use to infrastructure supporting third-generation (3G) wireless networks. Communication signals required by the 3G Partnership Project (3GPP) specifications for long-term evolution (LTE) will have to utilize carrier aggregation to meet the need for transmission bandwidth. Carrier aggregation refers to the use of more than one spectrum portion to deploy multiple component carriers to yield aggregated channels of wider transmission bandwidth (up to 100 MHz). Figure 1 illustrates the three carrier aggregation scenarios that are envisaged: 1) intraband contiguous carrier aggregation (contiguous component carriers aggregated in the same operating band), 2) intraband noncontiguous carrier aggregation (noncontiguous carriers aggregated in the same operating band), and 3) interband carrier aggregation (carrier aggregation of component carriers in different operating bands that may be contiguous or noncontiguous within each band).

Evolution of Monolithic Technology for Wireless Communications: GaN MMIC Power Amplifiers For Microwave Radios

This paper presents the progress of monolithic technology for microwaveapplication, focusing on gallium nitride technology advances in the realization of integratedpower amplifiers. Three design examples, developed for microwave backhaul radios, areshown. The first design is a 7 GHz Doherty developed with a research foundry, while thesecond and the third are a 7 GHz Doherty and a 7–15 GHz dual-band combined poweramplifiers, both based on a commercial foundry process. The employed architectures, themain design steps and the pros and cons of using gallium nitride technology are highlighted.The measured performance demonstrates the potentialities of the employed technology, andthe progress in the accuracy, reliability and performance of the process.

Challenges for energy efficient wide band gap semiconductor power devices

Wide band gap semiconductors, and in particular silicon carbide (4H-SiC) and gallium nitride (GaN), are very promising materials for the next generation of power electronics, to guarantee an improved energy efficiency of devices and modules. As a matter of fact, in the last decade intensive academic and industrial research efforts have resulted in the demonstration of both 4H-SiC MOSFETs and GaN HEMTs exhibiting VB2/Ron performances well beyond the silicon limits. In this paper, some of the present scientific challenges for SiC and GaN power devices technology are reviewed. In particular, the topics selected in this work will be the SiO2/SiC interface passivation processes to improve the channel mobility in 4H-SiC MOSFETs, the current trends for gate dielectrics in GaN technology and the viable routes to obtain normally-off HEMTs.

El nitruro de galio y sus aleaciones: ¡y se hizo la luz… azul!

El estudio de los dispositivos semiconductores emisores de luz azul ha sido un tema de trascendental importancia tanto desde el punto de vista científico como tecnológico. En el presente artículo se presta especial atención al desarrollo científico y tecnológico de los diodos emisores de luz y los diodos láser basados en la tecnología del nitruro de galio. Las principales propiedades del nitruro de galio y dos de sus aleaciones, el nitruro de indio-galio y el nitruro de aluminio-galio, se presentan cualitativamente. Una breve introducción a las nuevas fuentes de luz basadas en los dispositivos semiconductores emisores de luz sirve de base argumental para hacer una breve reseña histórica de la investigación, el desarrollo y la innovación llevadas a cabo por Isamu Akasaki, Hiroshi Amano y Shuji Nakamura que dieron como resultado el diseño, construcción y posterior comercialización de los diodos emisores de luz azul y láser de luz azul. Finalmente, se hace una valoración de la trascendencia social, económica y medioambiental del los dispositivos emisores de luz con base en la tecnología del nitruro de galio.

Envelope tracking of a radio frequency amplifier for Long Term Evolution using a three-level class-G modulator

Abstract. In this contribution, efficiency enhancement of a radio frequency (RF) power amplifier (PA) for Long Term Evolution (LTE) base stations using envelope tracking is investigated. The dynamically adapted drain bias voltage is provided by a three-level class-G modulator. The potential of this bias modulator is demonstrated with a class AB PA built in gallium nitride (GaN) technology with an operation frequency of 2.75 GHz, a maximum output power of 41 dBm and a peak power-added efficiency (PAE) of 60%. When driven by an LTE signal with a bandwidth of 20 MHz, overall system efficiency can be increased from 17% with a constant supply voltage up to 29% with envelope tracking. This is accompanied by a reduction of linearity. Adjacent channel leakage ratio (ACLR) decreases by 10 dB in the first and by 18 dB in the second adjacent channel, respectively. Error vector magnitude (EVM) increases from 9% up to 29%.

History of GaN: High-Power RF Gallium Nitride (GaN) from Infancy to Manufacturable Process and Beyond

In the early 1990s, gallium nitride (GaN) was deemed an excellent, next generation, semiconductor material for high power/high frequency transistors based on the material parameters of bandgap, electron mobility, and saturated electron velocity. The lack of bulk GaN source material led to the need for GaN growth on mismatched substrates such as Si, SiC and sapphire, but fundamental material development controlled the pace of maturation of GaN technology for both electronic and optoelectronic applications. The development of GaN for RF electronics was significantly aided by the intense development that occurred in the race to first production of blue and, eventually, white light-emitting diodes (LEDs). Ultimately, advancements in the growth of device-grade aluminum gallium nitride (AlGaN)/GaN heterostructures culminated in the demonstration of record power density RF amplifiers.

Introduction to the Focus Issue on Wide Bandgap Power Semiconductors

Wide bandgap (WBG) semiconductors, especially Silicon Carbide (SiC) and Gallium Nitride (GaN), offer unprecedented opportunities for transformative changes in electric utility and transportation infrastructures. Compared to semiconductor silicon, SiC and GaN offer significantly higher electrical and thermal conductivities, increased avalanche breakdown field strength, and improved ruggedness under extreme environmental operating conditions. These basic material properties translate into more compact and lightweight energy conversion systems with significant energy savings, much improved signal sensing and transmission characteristics, and longer operating lifetimes in the field. Commercial products that are poised to significantly benefit from SiC and GaN semiconductors include solid-state energy converters, power management electronics, power amplifiers, light-emitting diodes (LEDs), solar cells, lasers, and environmental sensors. The current global annual market potential for these products is collectively in excess of $100 billion. The potential annual market size for WBG power semiconductor devices alone now exceeds $30billionwithexponentialgrowthexpectedinthenextdecade.However, state-of-the-art commercial WBG power devices have limited voltage and current ratings, unproven field-reliability, and are prohibitively expensive. Consequently, the current global sales of WBG power devices is about $200 million per year. Realizing the current technology status and the vast commercial potential of WBG power semiconductor devices, an annual ECS Symposium on GaN and SiC Power Technologies was established in 2011. The2013Symposiumispoisedtobeveryexcitingandwillincludeoral presentations of more than 60 high-quality technical papers and two evening panel sessions involving in-depth discussion of topics ranging from materials to end-applications, and their inter-relationships, in order to understand and address the critical issues that are hindering rapid commercialization of WBG power technologies. Thisfocusissueincludesatotalof18full-lengthpeer-reviewedpapers. The focus issue begins with an overview paper that summarizes the current status and emerging trends in WBG power semiconductor devices from application considerations; the imminent need to reduce crystal defects in both bulk substrates and epitaxial layers is the highlight of this paper. There are a total of eight papers on SiC material technology.MorespecificallyonepaperonSiCbulksubstrategrowth, five papers on SiC homoepitaxy, one paper on SiC surface modification, and one paper on SiC material characterization. In addition, two papers on bulk GaN crystal growth and one paper on GaN-on-Si epitaxy are included. One paper deals with SiC and GaN wafer planarization,animportantprocessingtechniquepriortomaterialgrowth ∗ Electrochemical Society Active Member.

GaN Takes the Lead

Gallium nitride (GaN) technology is transforming RF monolithic microwave integrated circuits (MMICs) for power amplifiers (PAs), switches, low noise amplifiers, and more. Vendors are now producing GaN MMICs in volume and achieving outstanding performance. GaNs characteristics enable PA MMICs with 35 times the output power of GaAs alternatives or much smaller die sizes from L-band through Ka-band. High-power switches with low insertion loss up through 18 GHz have been developed. Low-noise amplifiers have been demonstrated with noise figures equivalent to gallium arsenide (GaAs) but with much higher input power survivability. The market for GaN RF MMICs spans commercial and military applications, including base station, cable television infrastructure, communications, radar and electronic warfare (EW), among others.

GaN for space application: almost ready for flight

On the last years, gallium nitride (GaN) technology has made a remarked breakthrough in the world of microwave electronics. Power transistors are now available. How this GaN technology would impact space-borne units is now a priority concern. Although the power capability of GaN technology is the first obvious profit, GaN could also be used for other applications like low noise amplifiers, mixers, and probably more. The high sustainable temperature of GaN transistors is most striking advantage for in-flight use. This is connected to packaging design which is also experiencing a lot of activities and quick progresses. Of course, space application is dependent upon the full demonstration of reliability and this constitutes another field of investigation. Finally, after 8 years of GaN studies, experimental results are presented: they open wide the road a revolution inside space-borne electronics: the rise of GaN.

Assembly of phosphonic acids on GaN and AlGaN

Self-assembled monolayers of octadecylphosphonic acid and 16-phosphonohexadecanoic acid (PHDA) were formed on the semiconductor substrates gallium nitride (GaN) and aluminium gallium nitride (AlGaN). The presence of the molecular layers was verified through x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Structural information was acquired with infrared spectroscopy which verified the bonding orientation of the carboxyl-containing PHDA. The impact of the molecular layers on the channel conductivity and the surface electronic structure of an AlGaN/GaN heterostructure was measured. Our results indicate that pinning of the surface Fermi level prohibits modification of the channel conductivity by the layer. However, a surface dipole of ∼0.8 eV is present and associated with both phosphonic acid layers. These results are of direct relevance to field-effect-based biochemical sensors and metal–semiconductor contact formation for this system and provide a fundamental basis for further applications of GaN and AlGaN technology in the fields of biosensing and microelectronics.

High-power monolithic AlGaN/GaN high electron mobility transistor switches

This work presents the design, fabrication, and test of X-band and 2–18 GHz wideband high-power single pole double throw (SPDT) monolithic microwave integrated circuit (MMIC) switches in microstrip gallium nitride (GaN) technology. Such switches have demonstrated state-of-the-art performances and RF fabrication yields better than 65%. In particular, the X-band switch exhibits 1 dB insertion loss, better than 37 dB isolation, and a power handling capability better than 39 dBm at a 1 dB insertion loss compression point; the wideband switch shows an insertion loss lower than 2.2 dB, better than 25 dB isolation, and an insertion loss compression of 1 dB at an input drive higher than 38.5 dBm in the entire bandwidth.

Blue Laser Diodes

AbstractThe first demonstration of a GaN‐based blue laser diode by Shuji Nakamura [1] was followed by a tremendous research and development effort around the world. Gallium nitride technology enables a range of novel applications with vast consumer markets. Examples are full‐color video displays, solid‐state lighting, and high‐definition DVD players. However, there still remains a strong need for a more detailed understanding of microscopic physical processes in nitride devices. Advanced models and numerical simulation can help to investigate those processes and to improve the device performance. This article reviews practical examples of GaN‐laser simulation, analysis, and optimization [2, 3].