Growth and Characterization of Novel Gan High Electron Mobility Transistor Structures with Enhanced Two-dimensional Electron Gas PDF Download

Author: Jeffrey R. Simpson
Publisher:
ISBN:
Category : Semiconductors
Languages : en
Pages : 330

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Book Description
Novel gallium nitride based high electron mobility transistor structures were grown using metalorganic chemical vapor deposition. Traditional GaN based HEMT structures incorporate a version of an aluminum gallium nitride / gallium nitride single crystalline heterointerface for generation of a conductive two-dimensional electron gas. The grown structures aim to enhance the properties of their two-dimensional electron gases beyond commercially available designs. Novel material alterations to the traditional HEMT structures have established a new materials platform for this technology. Growth and characterization of these novel materials are presented.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The physical properties of GaN, high saturation velocity, high breakdown fields, high electron mobility, wide bandgap energy and high thermal conductivity, make it a promising material for field effect transistor (FETs) devices for high speed, high power, and small channel length applications. Despite the success of GaN electronic devices such as heterojunction field effect transistors (HFETs), fabrication of GaN Metal Oxide Semiconductor (MOS) transistors remains a technical challenge. The primary reason for this is the non-availability of a gate dielectric with a low density of interface states and the simultaneous requirement of ohmic source/drain contacts which are compatible with enhancement mode structures. Unlike existing III-N HFET devices, which have a high free carrier density two dimensional electron gas (2DEG) in the semiconductor substrate, a MOSFET in either accumulation or inversion mode requires low free carrier concentration in the semiconductor channel, and a high density of free carriers in adjacent source and drain areas. This research explores the development, and demonstration of an enhancement mode (normally off) GaN MOSFET with highly doped source/drain ohmic contacts and compatible gate dielectric. Highly doped source/drain ohmic contacts were formed by selected area epitaxial regrowth of Si doped GaN by metalorganic chemical vapor deposition (MOCVD). The MOS gate dielectrics which have been investigated are Ga2O3/Gd2O3 and SiNx. To achieve uniform and highly doped GaN on reactive ion etched (RIE) and patterned GaN surfaces for source drain contacts, a low temperature regrowth (750-850oC) was developed. A model for growth morphology consistent with the low temperature regrowth of GaN on RIE patterned GaN surfaces is given. The detailed structural, optical, and chemical characterization of the low temperature regrown highly doped GaN for source and drain contacts has been provided. The structural characterization of GaN/Ga2O3/Gd2O3 interface.

Author: Eldad Bahat-Treidel
Publisher: Cuvillier Verlag
ISBN: 3736940947
Category : Science
Languages : en
Pages : 220

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Book Description
Gallium nitride (GaN)-based High Electron Mobility Transistors (HEMTs) for high voltage, high power switching and regulating for space applications are studied in this work. Efficient power switching is associated with operation in high OFF-state blocking voltage while keeping the ON-state resistance, the dynamic dispersion and leakage currents as low as possible. The potential of such devices to operate at high voltages is limited by a chain of factors such as subthreshold leakages and the device geometry. Blocking voltage enhancement is a complicated problem that requires parallel methods for solution; epitaxial layers design, device structural and geometry design, and suitable semiconductor manufacturing technique. In this work physical-based device simulation as an engineering tool was developed. An overview on GaN-based HEMTs physical based device simulation using Silvaco-“ATLAS” is given. The simulation is utilized to analyze, give insight to the modes of operation of the device and for design and evaluation of innovative concepts. Physical-based models that describe the properties of the semiconductor material are introduced. A detailed description of the specific AlGaN/GaN HEMT structure definition and geometries are given along with the complex fine meshing requirements. Nitride-semiconductor specific material properties and their physical models are reviewed focusing on the energetic band structure, epitaxial strain tensor calculation in wurtzite materials and build-in polarization models. Special attention for thermal conductivity, carriers’ mobility and Schottky-gate-reverse-bias-tunneling is paid. Empirical parameters matching and adjustment of models parameters to match the experimental device measured results are discussed. An enhancement of breakdown voltage in AlxGa1-xN/GaN HEMT devices by increasing the electron confinement in the transistor channel using a low Al content AlyGa1-yN back-barrier layer structure is systematically studied. It is shown that the reduced sub-threshold drain-leakage current through the buffer layer postpones the punch-through and therefore shifts the breakdown of the device to higher voltages. It is also shown that the punch-through voltage (VPT) scales up with the device dimensions (gate to drain separation). An optimized electron confinement results both, in a scaling of breakdown voltage with device geometry and a significantly reduced sub-threshold drain and gate leakage currents. These beneficial properties are pronounced even further if gate recess technology is applied for device fabrication. For the systematic study a large variations of back-barrier epitaxial structures were grown on sapphire, n-type 4H-SiC and semi-insulating 4H-SiC substrates. The devices with 5 μm gate-drain separation grown on n-SiC owning Al0.05Ga0.95N and Al0.10Ga0.90N back-barrier exhibit 304 V and 0.43 m × cm2 and 342 V and 0.41 m × cm2 respectively. To investigate the impact of AlyGa1-yN back-barrier on the device properties the devices were characterized in DC along with microwave mode and robustness DC-step-stress test. Physical-based device simulations give insight in the respective electronic mechanisms and to the punch-through process that leads to device breakdown. Systematic study of GaN-based HEMT devices with insulating carbon-doped GaN back-barrier for high voltage operation is also presented. Suppression of the OFF-state sub-threshold drain leakage-currents enables breakdown voltage enhancement over 1000 V with low ON-state resistance. The devices with 5 μm gate-drain separation on SI-SiC and 7 μm gate-drain separation on n-SiC exhibit 938 V and 0.39 m × cm2 and 942 V and 0.39 m × cm2 respectively. Power device figure of merit of ~2.3 × 109 V2/-cm2 was calculated for these devices. The impacts of variations of carbon doping concentration, GaN channel thickness and substrates are evaluated. Trade-off considerations in ON-state resistance and of current collapse are addressed. A novel GaN-based HEMTs with innovative planar Multiple-Grating-Field-Plates (MGFPs) for high voltage operation are described. A synergy effect with additional electron channel confinement by using a heterojunction AlGaN back-barrier is demonstrated. Suppression of the OFF-state sub-threshold gate and drain leakage-currents enables breakdown voltage enhancement over 700 V and low ON-state resistance of 0.68 m × cm2. Such devices have a minor trade-off in ON-state resistance, lag factor, maximum oscillation frequency and cut-off frequency. Systematic study of the MGFP design and the effect of Al composition in the back-barrier are described. Physics-based device simulation results give insight into electric field distribution and charge carrier concentration depending on field-plate design. The GaN superior material breakdown strength properties are not always a guarantee for high voltage devices. In addition to superior epitaxial growth design and optimization for high voltage operation the device geometrical layout design and the device manufacturing process design and parameters optimization are important criteria for breakdown voltage enhancement. Smart layout prevent immature breakdown due to lateral proximity of highly biased interconnects. Optimization of inter device isolation designed for high voltage prevents substantial subthreshold leakage. An example for high voltage test device layout design and an example for critical inter-device insulation manufacturing process optimization are presented. While major efforts are being made to improve the forward blocking performance, devices with reverse blocking capability are also desired in a number of applications. A novel GaN-based HEMT with reverse blocking capability for Class-S switch-mode amplifiers is introduced. The high voltage protection is achieved by introducing an integrated recessed Schottky contact as a drain electrode. Results from our Schottky-drain HEMT demonstrate an excellent reverse blocking with minor trade-off in the ON-state resistance for the complete device. The excellent quality of the forward diode characteristics indicates high robustness of the recess process. The reverse blocking capability of the diode is better than –110 V. Physical-based device simulations give insight in the respective electronic mechanisms. Zusammenfassung In dieser Arbeit wurden Galliumnitrid (GaN)-basierte Hochspannungs-HEMTs (High Electron Mobility Transistor) für Hochleistungsschalt- und Regelanwendungen in der Raumfahrt untersucht. Effizientes Leistungsschalten erfordert einen Betrieb bei hohen Sperrspannungen gepaart mit niedrigem Einschaltwiderstand, geringer dynamischer Dispersion und minimalen Leckströmen. Dabei wird das aus dem Halbleitermaterial herrührende Potential für extrem spannungsfeste Transistoren aufgrund mehrerer Faktoren aus dem lateralen und dem vertikalen Bauelementedesign oft nicht erreicht. Physikalisch-basierte Simulationswerkzeuge für die Bauelemente wurden daher entwickelt. Die damit durchgeführte Analyse der unterschiedlichen Transistorbetriebszustände ermöglichte das Entwickeln innovativer Bauelementdesignkonzepte. Das Erhöhen der Bauelementsperrspannung erfordert parallele und ineinandergreifende Lösungsansätze für die Epitaxieschichten, das strukturelle und das geometrische Design und für die Prozessierungstechnologie. Neuartige Bauelementstrukturen mit einer rückseitigen Kanalbarriere (back-barrier) aus AlGaN oder Kohlenstoff-dotierem GaN in Kombination mit neuartigen geometrischen Strukturen wie den Mehrfachgitterfeldplatten (MGFP, Multiple-Grating-Field-Plate) wurden untersucht. Die elektrische Gleichspannungscharakterisierung zeigte dabei eine signifikante Verringerung der Leckströme im gesperrten Zustand. Dies resultierte bei nach wie vor sehr kleinem Einschaltwiderstand in einer Durchbruchspannungserhöhung um das etwa Zehnfache auf über 1000 V. Vorzeitige Spannungsüberschläge aufgrund von Feldstärkenspitzen an Verbindungsmetallisierungen werden durch ein geschickt gestaltetes Bauelementlayout verhindert. Eine Optimierung der Halbleiterisolierung zwischen den aktiven Strukturen führte auch im kV-Bereich zu vernachlässigbaren Leckströme. Während das Hauptaugenmerk der Arbeit auf der Erhöhung der Spannungsfestigkeit im Vorwärtsbetrieb des Transistors lag, ist für einige Anwendung auch ein rückwärtiges Sperren erwünscht. Für Schaltverstärker im S-Klassenbetrieb wurde ein neuartiger GaN-HEMT entwickelt, dessen rückwärtiges Sperrverhalten durch einen tiefgelegten Schottkykontakt als Drainelektrode hervorgerufen wird. Eine derartige Struktur ergab eine rückwärtige Spannungsfestigkeit von über 110 V.

Author: Dong Ji
Publisher:
ISBN: 9780355764284
Category :
Languages : en
Pages :

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Gallium nitride (GaN)-based devices have entered the power electronics market and shown excellent progress in the medium power conversion applications. For power conversions applications > 10 kW, devices with vertical geometry are preferred over lateral geometry, since the former allows more current for a given chip area, thus provides a more economical solution for high-voltage and high-current applications. Moreover, the vertical geometry is attractive for its dispersion-free performance without passivation, a phenomenon that causes high dynamic on-state resistance (R[subscript on]) in lateral geometry high electron mobility transistors (HEMTs). In this study, GaN-based vertical transistors, which include trench current aperture vertical electron transistors (CAVETs) and in-situ oxide, GaN interlayer based trench field-effect transistors (OGFETs), have been studied both theoretically and experimentally. In order to model the devices for DC and switching performances, a device/circuit hybrid simulation platform was developed based on Silvaco ATLAS. The validation of the model was obtained by calibrating it against commercially available HEMT data. Using this hybrid model, one can start with a two-dimensional (2D) drift-diffusion model of the device and build all the way up to its circuit implementation to evaluate its switching performance. The hybrid model offers an inexpensive and accurate way to project and benchmark the performance and can be extended to any GaN-based power transistors.In the experimental portion of this study, a high voltage OGFET was designed and fabricated. An OGFET shows improved characteristics owing to a 10 nm unintentionally doped (UID) GaN interlayer as the channel. A normally-off (V[subscript th] = 4 V) vertical GaN OGFET with 10 nm UID-GaN channel interlayer and 50 nm in-situ Al2O3 was successfully demonstrated and scaled for higher current operation. By using a novel double-field-plated structure for mitigating peak electric field, a higher off-state breakdown voltage over 1.4 kV was achieved with a significantly low specific on-state resistance (R[subscript on,sp]) of 2.2 m[omega] cm2. The metal-organic chemical vapor deposition (MOCVD) regrown 10 nm GaN channel interlayer enabled a channel resistance lower than 10 [omega] mm with an average channel electron mobility of 185 cm2/Vs. The fabricated large area transistor with a total area of 0.4 mm × 0.5 mm offered a breakdown voltage of 900 V and an Ron of 4.1 [omega]. Results indicate the potential of vertical GaN OGFET for greater than 1 kV range of power electronics applications.In addition to the OGFET, the CAVET with a trench gate structure was studied in this work. By taking advantage of the two-dimensional electron gas (2DEG) in the AlGaN/GaN structure, the trench CAVET can secure an even higher channel electron mobility compared to the OGFET. The first functional trench CAVET with a metal-insulator-semiconductor (MIS) gate structure was fabricated in this work with a breakdown voltage of about 225 V. With the improvement in the fabrication process, an 880 V device with an R[subscript on,sp] of 2.7 m[omega] cm2 was demonstrated. One of the notable features of the fabricated trench CAVET is that it requires a standard MOCVD growth condition for HEMT epilayers. The simplification of the growth process is a significant achievement. Finally, a regrowth-free CAVET was demonstrated and patented. The transformative approach was realized using Si ion implantation based doping compensation in the aperture.

Author: Robert F Davis
Publisher: World Scientific
ISBN: 9814482692
Category : Technology & Engineering
Languages : en
Pages : 295

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Book Description
The unique materials properties of GaN-based semiconductors have stimulated a great deal of interest in research and development regarding nitride materials growth and optoelectronic and nitride-based electronic devices. High electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown field, and low thermal impedance of GaN-based films grown over SiC or bulk AlN substrates make nitride-based electronic devices very promising. The chemical inertness of nitrides is another key property.This volume, written by experts on different aspects of nitride technology, addresses the entire spectrum of issues related to nitride materials and devices, and it will be useful for technologists, scientists, engineers, and graduate students who are working on wide bandgap materials and devices. The book can also be used as a supplementary text for graduate courses on wide bandgap semiconductor technology.

Author: Jaime Alberto Zamudio Flores
Publisher: kassel university press GmbH
ISBN: 3862193640
Category : Gallium nitride
Languages : en
Pages : 257

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This work presents a comprehensive modeling strategy for advanced large-size AlGaN/GaN HEMTs. A 22-element equivalent circuit with 12 extrinsic elements, including 6 capacitances, serves as small-signal model and as basis for a large-signal model. ANalysis of such capacitances leads to original equations, employed to form capacitance ratios. BAsic assumptions of existing parameter extractions for 22-element equivalent circuits are perfected: A) Required capacitance ratios are evaluated with device's top-view images. B) Influences of field plates and source air-bridges on these ratios are considered. The large-signal model contains a gate charge's non-quasi-static model and a dispersive-IDS model. THe extrinsic-to-intrinsic voltage transformation needed to calculate non-quasi-static parameters from small-signal parameters is improved with a new description for the measurement's boundary bias points. ALl IDS-model parameters, including time constants of charge-trapping and self-heating, are extracted using pulsed-DC IV and IDS-transient measurements, highlighting the modeling strategy's empirical character.

Author: Michael James Murphy
Publisher:
ISBN:
Category :
Languages : en
Pages : 226

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Author: Erdin Ture
Publisher: Fraunhofer Verlag
ISBN: 9783839613412
Category : Technology & Engineering
Languages : en
Pages : 0

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The rapidly-growing data throughput rates in a wide range of wireless communication applications are pushing the established semiconductor device technologies to their limits. Considerably higher levels of solid-state output power will therefore be needed to meet the demand in the next generation satellite communications as well as the RADAR systems. Owing to their superior material properties such as high breakdown fields and peak electron velocities, GaN-based high electron mobility transistors (HEMTs) have recently prevailed in high-power systems operating in the microwave frequency bands. On the other hand at the millimetre-wave (MMW) and sub-MMW frequencies, highly-scaled GaN HEMTs are prone to experiencing deteriorated high frequency characteristics which severely limit the high-power performance. In an attempt to overcome this, 3-dimensional GaN HEMT devices featuring the Tri-gate topology are developed in this work, exhibiting enhanced performance in terms of both off- and on-state figures of merit. The demonstrated results promote the great potential of Tri-gate GaN HEMTs for both MMW power amplifier and high-speed logic applications.

Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 684

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Author: Alex Lidow
Publisher: John Wiley & Sons
ISBN: 1118844785
Category : Science
Languages : en
Pages : 266

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Gallium nitride (GaN) is an emerging technology that promises to displace silicon MOSFETs in the next generation of power transistors. As silicon approaches its performance limits, GaN devices offer superior conductivity and switching characteristics, allowing designers to greatly reduce system power losses, size, weight, and cost. This timely second edition has been substantially expanded to keep students and practicing power conversion engineers ahead of the learning curve in GaN technology advancements. Acknowledging that GaN transistors are not one-to-one replacements for the current MOSFET technology, this book serves as a practical guide for understanding basic GaN transistor construction, characteristics, and applications. Included are discussions on the fundamental physics of these power semiconductors, layout and other circuit design considerations, as well as specific application examples demonstrating design techniques when employing GaN devices. With higher-frequency switching capabilities, GaN devices offer the chance to increase efficiency in existing applications such as DC–DC conversion, while opening possibilities for new applications including wireless power transfer and envelope tracking. This book is an essential learning tool and reference guide to enable power conversion engineers to design energy-efficient, smaller and more cost-effective products using GaN transistors. Key features: Written by leaders in the power semiconductor field and industry pioneers in GaN power transistor technology and applications. Contains useful discussions on device–circuit interactions, which are highly valuable since the new and high performance GaN power transistors require thoughtfully designed drive/control circuits in order to fully achieve their performance potential. Features practical guidance on formulating specific circuit designs when constructing power conversion systems using GaN transistors – see companion website for further details. A valuable learning resource for professional engineers and systems designers needing to fully understand new devices as well as electrical engineering students.