Gallium Nitride Semiconductor Research Articles

Investigation of Current Collapse Mechanism on AlGaN/GaN Power Diodes

In this paper, a methodology is proposed for studying the current collapse effects of Gallium Nitride (GaN) power diodes and the consequences on the dynamic on-resistance (RON). Indeed, the growing interest of GaN based, high frequency power conversion requires an accurate characterization and a deep understanding of the device’s behaviour before any development of power converters. This study can ultimately be used to model observed trap effects and, thus, improve the equivalent electrical model. Using an in-house circuit and a specific experimental setup, a current-collapse phenomenon inherent to gallium nitride semiconductor is studied on planar 650 V—6 A GaN diodes by applying high voltage stresses over a wide range of temperatures. With this method, useful data on activation energy and capture cross section of electrical defects linked to dynamic RON are extracted. Finally, the origins of such defects are discussed and attributed to carbon-related defects.

P‐10.7: Investigation of Fabrication Technologies of GaN‐based Micro‐LED Devices

Micro-light-emitting diode (Micro-LED) is a new type of display device based on the third-generation semiconductor gallium nitride (GaN) material. Micro-LED has been applied to micro-display technology due to its huge development potential. However, the EQE of Micro-LEDs decreases with the decrease of the side wall defects, and the passivation process can reduce the sidewall damage and improve the EQE. In this study, the fabrication technology of Micro-LEDs was summarized and InGaN/GaN multi-quantum wells (MQWs) Micro-LEDs from 10 × 10 μm to 200 × 200 μm were fabricated. The improvement effect of different passivation materials on the electrical characteristics of Micro-LEDs was explored. The results showed that passivation materials could effectively reduce the leakage of the device, reduce the sidewall damage and reduce the ideal factor, among which Si3N4 had the most obvious effect.

What Will Win the Wide-Bandgap Wars?

The answer is a resounding yes. Such a change is actually well underway. Starting around 2001, the compound semiconductor gallium nitride fomented a revolution in lighting that has been, by some measures, the fastest technology shift in human history. In just two decades, the share of the global lighting market held by gallium-nitride-based light-emitting diodes has gone from zero to more than 50 percent, according to a study by the International Energy Agency. The research firm Mordor Intelligence recently predicted that, worldwide, LED lighting will be responsible for cutting the electricity used for lighting by 30 to 40 percent over the next seven years. Globally, lighting accounts for about 20 percent of electricity use and 6 percent of carbon dioxide emissions, according to the United Nations Environment Program.

Gallium Arsenide and Gallium Nitride Semiconductors for Power and Optoelectronics Devices Applications

The advancement in technology in semiconductor materials significantly contributed in improvement of human life by bringing breakthrough in fabrication of optoelectronics and power devices which have wide applications in medicine and communication. The Gallium Arsenide (GaAs) and Gallium Nitride (GaN) are versatile materials for such applications but with relative merits and demerits. GaAs transistors are suitable for both narrowband and wideband applications due to very wide operating frequency range (30 MHz to millimetre-wave frequencies as high as 250 GHz). They are highly sensitive, generate very little internal noise and have power density typically around 1.5 W/mm. But low break down voltage (5x105V/cm), low output power (5-10W) and inability to withstand higher temperatures are the main limitations. On the other hand, GaN possess the improved physical and chemical characteristics, with high output power, high operating temperature (1000°C in vacuum), fast heat dissipation, high breakdown voltage (4x106V/cm), high power density (5-12W/mm), high frequency characteristics and large band gap (3.4eV) which allow significant reduction of devise size. Also high breakdown voltage increases the overall impedance which make it suitable in matching process and enables efficient operation in broad band region. The present paper critically analyses the GaAs and GaN semiconductors in relation to their significant physical and chemical properties, which make them suitable to make efficient power and optoelectronics devices for applications in communication, space and medicine.

Wireless photoelectrochemical mechanical polishing for inert compound semiconductor wafers

Chemical mechanical polishing (CMP) remains the necessary polishing technology in chip manufacturing, but its applications on inert n-type gallium nitride (GaN) and carborundum (SiC) semiconductors are inefficient. Based on the mechanism of bipolar photoelectrochemistry, an efficient wireless photoelectrochemical mechanical polishing (WPECMP) method was proposed. The method applies a wireless electric field to the ultraviolet (UV) light-irradiated semiconductor wafer to separate photogenerated electron-hole pairs during polishing, rather than the traditional wire-connecting wafer to a power source. WPECMP is thus a universal polishing method for freestanding and semiconductor-on-insulator substrate wafers. The material removal rate (MRR) may reach ~μm h−1 level because the unpaired holes oxidize the wafer to accelerate the material removal in the mechanical polishing process. An apparatus was devised to allow the wafer to alternate between oxidation and mechanical polishing, and the method was validated by finishing GaN wafers that are inert in CMP processing. The best MRR achieved 1.2 μm h−1, one order of magnetite higher than that of the CMP technology. The WPECMP method enables wafers to achieve a damage-free surface/subsurface, a surface roughness (Sa) of less than 0.082 nm in 5 × 5 μm2, and a surface flatness of less than 3.2 nm over 45 mm. The study opens a way to develop ultra-precision processing technologies with wireless electric field assistance.

Computational-fitting method for mobility extraction in GaN HEMT.

The third-generation semiconductor gallium nitride (GaN) has drawn wide attention due to its high electron mobility property. However, the classical mobility calculation methods such as Hall effect and transfer length method have limitations in accurately extracting the mobility of GaN High Electron Mobility Transistor (HEMT) due to their inability to consider the resistance in non-gate region or their high fabrication costs. This work proposes an effective yet accurate computational-fitting method for extracting the mobility of GaN HEMT. The method consists of measuring the total resistance between source and drain at different gate voltages over a very small range of overdrive voltage variations, when the sum of the transconductance and capacitance of the device is regarded as constants, and fitting a unique function of the total resistance with respect to the overdrive voltage to determine the carrier mobility and the non-gate resistance. The feasibility and reliability of the method has been also verified.

Theoretical Investigations on Mechanical and Ultrasonic Characteristics of Gallium Nitride Semiconductor under High Pressure

Theoretical Investigations on Mechanical and Ultrasonic Characteristics of Gallium Nitride Semiconductor under High Pressure

Development of a method for calculating effective displacement damage doses in semiconductors and applications to space field.

The displacement damage dose (DDD) is a common index used to predict the life of semiconductor devices employed in space-based environments where they will be exposed to radiation. The DDD is commonly estimated from the non-ionizing energy loss based on the Norgett-Robinson-Torrens (NRT) model, although a new definition for a so-called effective DDD considers the molecular dynamic (MD) simulation with the amorphization in semiconductors. The present work developed a new model for calculating the conventional and effective DDD values for silicon carbide (SiC), indium arsenide (InAs), gallium arsenide (GaAs) and gallium nitride (GaN) semiconductors. This model was obtained by extending the displacement per atom tally implemented in the particle and heavy ion transport code system (PHITS). This new approach suggests that the effective DDD is higher than the conventional DDD for arsenic-based compounds due to the amorphization resulting from direct impacts, while this relationship is reversed for SiC because of recombination defects. In the case of SiC and GaN exposed to protons, the effective DDD/conventional DDD ratio decreases with proton energy. In contrast, for InAs and GaAs, this ratio increases to greater than 1 at proton energies up to 100 MeV and plateaus because the defect production efficiency, which is the ratio of the number of stable displacements at the end of collision cascade simulated by MD simulations to the number of defects calculated by NRT model, does not increase at damage energy values above 20 keV. The practical application of this model was demonstrated by calculating the effective DDD values for semiconductors sandwiched between a thin glass cover and an aluminum plate in a low-Earth orbit. The results indicated that the effective DDD could be dramatically reduced by increasing the glass cover thickness to 200 μm, thus confirming the importance of shielding semiconductor devices used in space. This improved PHITS technique is expected to assist in the design of semiconductors by allowing the effective DDD values for various semiconductors having complex geometries to be predicted in cosmic ray environments.

(Invited) Vertical Gallium Nitride Mosfets for Electric Drivetrains

Wide-bandgap semiconductors have a significant advantage over conventional Si-based electronics by leveraging materials properties to achieve higher breakdown voltage, lower on-resistance, and high-frequency operation. For electric vehicle drivetrains, this translates to higher efficiency and power density, resulting in more miles driven per charge. This move towards wide-bandgap power electronics is necessary to achieve the U.S. Department of Energy (DOE) power electronics density target of 100 kW/L.Vertical gallium nitride-based power devices are expected to exceed Si and even SiC-based systems with the promise of increased performance and power density. Compared to lateral GaN devices, a vertical topology promotes more efficient scaling towards high-power applications, where both high voltage and high current are necessary. This talk describes our team’s effort towards developing vertical GaN MOSFETs. The results of Sandia’s first-generation device demonstrator serve as a milestone in the path of producing devices rated for 1200-V and 100-A operation.The vertical GaN trench MOSFET is unique compared to Si- or SiC-alternatives in that the doped layers comprising the source and body regions are grown by epitaxy rather than formed by ion implantation. Challenges with selective-area doping in GaN add additional complexity to the design of a trench MOSFET. In addition, the lack of a high-quality native oxide in GaN means that the gate dielectric must be deposited rather than thermally grown. The devices produced at Sandia rely on atomic-layer-deposited thin films for the gate dielectric (primarily Al2O3 or SiO2). First-generation results demonstrate devices capable of 400 mA/mm drain current, 108 on/off ratio, and a positive threshold voltage near 8 V. More recently, devices capable of blocking 500 V in the off-state have been demonstrated. Device failure in the off-state results from high fields in the gate dielectric, which can be minimized by reducing the trench etch depth or by increasing the voltage rating of the drift region. However, further shielding of the gate dielectric to achieve substantially higher off-state voltages requires significant changes to the device architecture which are reliant on selective-area doping. In addition, device-killing defects either from the starting substrate, the epitaxy, or defects introduced during processing limit yield for large-area devices and present a substantial obstacle to scale devices for high-current operation. Hence, methods for reducing cell pitch and increasing packing density are highly valued. In this talk, we will discuss the path forward for achieving higher breakdown voltages and high-current operation using GaN-specific strategies to achieve better performing devices, as well as some of the challenges for vertical GaN development. This work provides a foundational platform for developing next-generation power electronics that employ wide bandgap, gallium nitride semiconductors. This work was supported by the Electric Drivetrain Consortium managed by Susan Rogers of DOE’s Vehicle Technologies Office. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Figure 1

Recent progress on the vertical GaN power transistor and its integrated circuit

<p indent="0mm">Silicon (Si) material is the mainstream semiconductor material for a long time because of its relatively excellent high-temperature resistance, radiation resistance, low price, and huge reserves. However, with the rapid development of power electronics technology, the development of technology has reached a bottleneck period, and Moore’s law has gradually failed. The existing silicon-based semiconductor devices are close to the theoretical limit of Si materials and can no longer meet the performance requirements of future power devices. However, the cost of transistors is constantly rising, and the performance improvement is slow, gradually moving towards the post-Moore era. To further improve the performance of the device, it is necessary to seek new technologies or new materials to support the continuous development of power devices, and the core of the progress of power semiconductor devices is the development of semiconductor materials. As the third generation of wide band gap semiconductors, gallium nitride (GaN) has been superior to Si in terms of material properties. GaN has the advantages of a wide band gap, high critical field strength, high electron saturation velocity, high conductivity, high-temperature resistance, and high voltage resistance. Compared with traditional Si-based power devices, it not only has higher breakdown voltage, low on-resistance, high electron mobility and good thermal conductivity, but also has smaller device volume and better heat dissipation performance under the same performance, which greatly reduces power consumption and achieves the effect of energy saving and emission reduction. The cost of early GaN single crystal preparation and epitaxial growth is beyond reach. However, with the mature development of growth technology, not only the cost of GaN single crystal substrate and its epitaxial growth is decreasing, but also the quality is gradually increasing, which lays a solid foundation for the wide application of GaN power devices in the future. This paper lists the main physical parameters of GaN and other semiconductor materials, the preparation of GaN single crystal, and the main methods of its epitaxy growth, and describes the advantages of GaN power devices in the current environment. For the device structure, the problems of the lateral device and the advantages of the vertical device are listed, and why the vertical device can become the mainstream structure of future power devices is explained. On this basis, the structure, working principle, research progress, and existing problems of vertical current aperture GaN transistor (CAVET), trench GaN MOSFET, vertical trench MOSFET based on <italic>in-situ</italic> oxidation GaN interlayer (GaN OG-FET), and vertical GaN fin field effect transistor (GaN FinFET) are introduced in detail. The performance parameters of vertical GaN power transistors mentioned in this paper are summarized in tables according to device types and time sequence, and the general direction of the development of GaN power transistors in the future is proposed. For integrated circuit systems, the special requirements and key technologies of GaN power devices in driver chips are summarized. Finally, for the current market environment, listing the vertical GaN power transistor in the medium and low voltage range is a more popular and promising application scenario.

A Pathway to Fabricate Gallium Nitride Embedded 3D High‐Index‐Contrast Optical Structures

AbstractOptical engineering of gallium nitride (GaN) semiconductor material has enabled novel applications and technologies. 3D optical engineering is challenging and mostly accomplished by surface‐level patterning with subtractive or additive means. In this work a pathway, based on epitaxial conductivity control in conjunction with ion implant and subsequent electrochemical etching, to generate complex embedded nanoporous (NP)‐GaN/GaN or air/GaN 3D optical structures is presented. A range of subsurface structures is demonstrated including in‐plane NP‐GaN stripes and curved patterns, air/GaN microchannels, and localized, embedded distributed Bragg reflectors (DBRs) as micromirrors. To further demonstrate the versatility of the technique, adjacent DBR micromirrors, of different thicknesses, embedded depths, and widths, are created in the same fabrication steps. Computer simulations are used to shed light on the limitations of feature sizes of the presented technique. The approach is a simple, scalable, and versatile approach for fabricating embedded 3D optical structures readily extendable beyond GaN semiconductors.

Investigation of Advanced GaN and SiC Semiconductor Materials: Key Characteristics and Diverse Applications

The development of wide band gap (WBD) semiconductor materials has gained enormous attention to, and among all the materials, gallium nitride (GaN) and silicon carbide (SiC) are at heart because of their high-temperature endurance and enormous potential in high voltage uses. This article summarizes both materials' basics and current status, starting from comparatively illustrating their distinctive merits, such as high breakdown voltage and excellent thermal conductivity. Followed up is a critical overview of various facile preparation strategies, and the advantages and disadvantages of the methods are concluded shortly. Finally, the real-world applications of these two materials are presented and analyzed, and both similar and unique uses for GaN and SiC are illustrated. The bright future of both materials is concluded, and this article clarifies the information needed for both materials throughout the progression.

Room‐Temperature Printing of Ultrathin Quasi‐2D GaN Semiconductor via Liquid Metal Gallium Surface Confined Nitridation Reaction

AbstractOutstanding wide‐bandgap semiconductor material such as gallium nitride (GaN) has been extensively utilized in power electronics, radiofrequency amplifiers, and harsh environment devices. Due to its quantum confinement effect in enabling desired deep‐ultraviolet emission, excitonic impact, and electronic transport features, 2D or ultrathin quasi‐2D GaN semiconductors have been one of the most remarkable candidates for future growth of microelectronic devices. Here, for the first time, the authors report a large area, wide bandgap, and room‐temperature quasi‐2D GaN synthesis and printing strategy through introducing the plasma medicated liquid metal gallium surface‐confined nitridation reaction mechanism. The developed direct fabrication and compositional process is consistent with various electronics manufacturing approaches and thus opens an easy going way for cost‐effective growth of the third‐generation semiconductor. In particular, the fully printed field‐effect transistors relying on the GaN thus made show p‐type switching with an on/off ratio greater than 105, maximum field‐effect hole mobility of 53 cm2 V−1 s−1, and a small sub‐threshold swing. As demonstrated, the present method allows to produce at room temperature the GaN with thickness spanning from 1 nanometer to nanometers. This basic method can be further extended, generalized, and utilized for making various electronic and photoelectronic devices in the coming time.

Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices.

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction of wide band gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), which opened new perspectives for high-κ materials in these emerging technologies. In this context, aluminium and hafnium oxides (i.e., Al2O3, HfO2) and some rare earth oxides (e.g., CeO2, Gd2O3, Sc2O3) are promising high-κ binary oxides that can find application as gate dielectric layers in the next generation of high-power and high-frequency transistors based on SiC and GaN. This review paper gives a general overview of high-permittivity binary oxides thin films for post-Si electronic devices. In particular, focus is placed on high-κ binary oxides grown by atomic layer deposition on WBG semiconductors (silicon carbide and gallium nitride), as either amorphous or crystalline films. The impacts of deposition modes and pre- or postdeposition treatments are both discussed. Moreover, the dielectric behaviour of these films is also presented, and some examples of high-κ binary oxides applied to SiC and GaN transistors are reported. The potential advantages and the current limitations of these technologies are highlighted.

New FOM-Based Performance Evaluation of 600/650 V SiC and GaN Semiconductors for Next-Generation EV Drives

The drive inverter represents a central component of an electric vehicle (EV) drive train, being responsible for the DC/AC power conversion between the battery and the electrical machine. In this context, novel converter topologies adopting modern 600/650V wide bandgap (WBG) semiconductor devices will play a crucial role in improving the performance of next-generation drive inverters. In fact, WBG devices theoretically allow to achieve both higher inverter power density and higher conversion efficiency with respect to conventional silicon (Si) IGBT based solutions. Even though silicon carbide (SiC) devices are already well established in the automotive industry, high-voltage gallium nitride (GaN) devices are rapidly entering the market, promising higher theoretical performance but featuring a lower degree of maturity. As a consequence, it is currently not clear which semiconductor technology is most suited for future EV drive inverters. Therefore, this paper aims to address this gap providing a comparative performance evaluation of state-of-the-art SiC and GaN 600/650V active switches. In particular, a novel figure-of-merit (FOM) representing the minimum theoretical semiconductor losses under hard-switching operation is introduced. Remarkably, this FOM enables a fair and accurate performance comparison among semiconductor devices, allowing to clearly determine the best performing technology for a given set of application-specific conditions. The results of the comparative assessment show that currently available SiC and GaN active switch technologies can outperform each other depending on the semiconductor operating temperature and the converter switching frequency.

Determination of Enriched Quantum Efficiency with InGaN/GaN Multiple Quantum Well Solar Cells

Background: Energy is a major concern in every aspect of our life. Solar energy is a renewable environmentally friendly source of energy. Therefore, solar cells are vastly studied with different technology and different material. Objective: The main objective here is to analyze InGaN material for solar cell applications with less complicated structures of MQW solar cells on revising solar cell with the recombination structure, I-V characteristics, and its efficiency. Methods: The device is simulated using SILVACO ATLAS, where the well and the barrier layers are inserted in the depletion region employing material combination of InGaN / GaN, which increases the solar cell performance parameter. This work focuses on the photogeneration rate, recombination in the active region as well as its current-voltage relation from the simulation. Results: With the increase in the number of QW periods in the active region of the device, the photovoltaic parameters especially conversion efficiency, increases significantly. Under space AM0 solar illumination, the cell efficiency increases up to 8.2 % for 20 MQWs with 20% Indium content for the InGaN/GaN structure. It enhances the External Quantum Efficiency (EQE) upto 36% at nearly 380nm wavelength range near the UV region. Conclusion: The modelled structure is efficiently simulated using TCAD SILVACO ATLAS, and the material Indium Gallium Nitride semiconductor shows an excellent solar cell performance with high solar radiation. It is also observed that with an increase in the number of well periods the solar cell performance increases, which demonstrates the feasibility of Indium Gallium Nitride solar cell with an additional MQW period as a power source.

Electrochemical Affinity Sensors Using Field Effect Transducer Devices for Chemical Analysis

AbstractThe review presents advances and main challenges of the affinity sensors based on field‐ effect transistors published during the last five years. The different nanomaterial‐based field‐effect transistors are classified according to the nature of the nanomaterials, beginning by silicon, the “gold‐standard” semiconductor, the gallium nitride semiconductor, the organic semiconductors, the silicon nanowires, the inorganic nanomaterials, the carbon nanotubes and the graphene. Due to its exceptional electrical properties, the main works are devoted to graphene. The obtained analytical performances for the detection of biomarkers, of DNA sequences and of miRNA are listed. The relation between the operational conditions ‐ nature of the nanomaterials, procedure of preparation, choice of the receptor molecule, method of immobilization – and the analytical performance are discussed. The perspective of industrialization of these affinity sensors based on field‐effect transistors is discussed.

Uniting GaN Electronics and Photonics on A Single Chip

The bandgap energies of the group III-V semiconductor gallium nitride (GaN) and its alloys cover emission wavelengths ranging from the ultraviolet to the visible. Concurrently, GaN has enabled high performance transistors to provide attractive solutions in the high voltage and high frequency regimes. Both GaN optoelectronics and electronics have been successfully developed, and the two technologies are often dependent on each other in many real-life applications. In the simplest case, both the GaN light-emitting diode (LED) and photodiode have to be driven or amplified by transistor-based circuits. However, these circuits are separately made on the Si platform. What if GaN optoelectronics and electronics can be integrated onto the same platform? That would result in significant reduction in material costs, processing costs and packaging costs. At the same time, the performance of the monolithically integrated system will be significantly improved, due to reduced resistances and parasitic capacitances. In view of such prospects, we propose and characterize monolithically integrated GaN metal-oxide-semiconductor field effect transistors (MOSFETs), transmitter, waveguide, and receiver, which are fabricated onto a conventional InGaN/GaN LED wafer without involving re-growth or post-growth doping (diffusion or ion implantation). The capability of integrating optoelectronics (transmitter, waveguide, receiver) with MOSFETs would inevitably open up new horizons for the GaN platform.

AlGaN/GaN magnetic sensors featuring heterojunction 2DEG channel

Magnetic sensors based on the principle of Hall effect are widely used in various applications for detection and control of displacement, speed, angle, and rotation speed. Nowadays, the conventional Hall sensors are made of the narrow bandgap semiconductors. The typical ones are silicon (Si), indium antimonide (InSb), and gallium arsenide (GaAs). With the rapid increase in the need for high-temperature magnetic detections especially in the space exploration and thermonuclear power stations, they cannot meet the requirement of operation at high temperature due to the limitation of their natural characteristics such as low carrier mobility or small bandgap. In this work, the Hall sensors based on the third-generation semiconductor gallium nitride (GaN) were demonstrated by employing both the simulation and device fabrication schemes. The developed AlGaN/GaN heterojunction Hall sensors benefited from the presence of two-dimensional electron gas (2DEG) are small in size, and have an improved magnetic sensitivity and stability at high temperature. They exhibit a large current-related magnetic sensitivity up to 94.6 V A−1 T−1 and a low temperature coefficient less than 745 ppm K−1, which is obviously improved compared with those in the currently commercialised semiconductor Hall sensors. Moreover, the Hall sensors developed in this work can be widely used in various harsh environments with high temperature (>573 K) and intense radiation in future.

Efficiency optimization of totem pole PFC with Gallium Nitride semiconductors

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.