Technology and Characterization of GaN-based Heterostructure Field Effect Transistors (HFETs) PDF Download
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Author: Michael Fieger
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Languages : en
Pages : 0
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Author: Michael Fieger
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Languages : en
Pages : 0
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Author: Qian Fan
Publisher:
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Category : Semiconductors
Languages : en
Pages :
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This dissertation is focused on the research efforts to develop the growth, processing, and modeling technologies for GaN-based Heterojunction Field Effect Transistors (HFETs). The interest in investigating GaN HFETs is motivated by the advantageous material properties of nitride semiconductor such as large band gap, large breakdown voltage, and high saturation velocity, which make it very promising for the high power and microwave applications. Although enormous progress has been made on GaN transistors in the past decades, the technologies for nitride transistors are still not mature, especially concerning the reliability and stability of the device. In order to improve the device performance, we first optimized the growth and fabrication procedures for the conventional AlGaN barrier HFET, on which high carrier mobility and sheet density were achieved. Second, the AlInN barrier HFET was successfully processed, with which we obtained improved I-V characteristics compared with conventional structure. The lattice-matched AlInN barrier is beneficial in the removal of strain, which leads to better carrier transport characteristics. Furthermore, new device structures have been examined, including recess-gate HFET with n+ GaN cap layer and gate-on-insulator HFET, among which the insertion of gate dielectrics helps to leverage both DC and microwave performances. In order to depict the microwave behavior of the HFET, small signal modeling approaches were used to extract the extrinsic and intrinsic parameters of the device. An 18-element equivalent circuit model for GaN HFET has been proposed, from which various extraction methods have been tested. Combining the advantages from the cold-FET measurements and hot-FET optimizations, a hybrid extraction method has been developed, in which the parasitic capacitances were attained from the cold pinch-off measurements while the rest of the parameters from the optimization routine. Small simulation error can be achieved by this method over various bias conditions, demonstrating its capability for the circuit level design applications for GaN HFET. Device physics modeling, on the other hand, can help us to reveal the underlying physics for the device to operate. With the development of quantum drift-diffusion modeling, the self-consistent solution to the Schrödinger-Poisson equations and carrier transport equations were fulfilled. Lots of useful information such as band diagram, potential profile, and carrier distribution can be retrieved. The calculated results were validated with experiments, especially on the AlInN layer structures after considering the influence from the parasitic Ga-rich layer on top of the spacer. Two dimensional cross-section simulation shows that the peak of electrical field locates at the gate edge towards the drain, and of different kinds of structures the device with gate field-plate was found to efficiently reduce the possibility of breakdown failure.
Author: Bravishma Narayan
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Category : Field-effect transistors
Languages : en
Pages :
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This thesis describes the design, fabrication and characterization of AlGaN/GaN Heterostructure Field E ect Transistors (HFETs) grown by a Metal Organic Chemical Vapor Deposition (MOCVD) on sapphire substrates. The objective of this research is to develop AlGaN/GaN power devices with high breakdown voltage (greater than 1 kV) and low turn-on resistance. Various characteristics such as current drive (Idss), transconductance (gm) and threshold voltage (Vth) have also been measured and the results have been discussed. Two major challenges with the development of high breakdown voltage AlGaN/GaN HFETs in the past have been high material defect density and non-optimized fabrication technologies which gives rise to bu er leakage and surface leakage, respectively. In this thesis, mesa isolation, ohmic and gate metal contacts, and passivation techniques, have been discussed to improve the performance of these power transistors in terms of low contact resistance and low gate leakage. The relationship between breakdown voltage and Rds(ON)A with respect to the gate-drain length (Lgd) is also discussed. First, unit cell devices were designed (two-fingered cells with Wg = 100, 300, 400 m) and characterized, and then they were extended to form large area devices (upto Wg = 40 mm). The design goals were classied into three parts: : - High Breakdown Voltage: This was achieved by designing devices with variations in Lgd,
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Languages : en
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Author: Michael Shur
Publisher: World Scientific
ISBN: 9789812562364
Category : Technology & Engineering
Languages : en
Pages : 310
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The unique materials properties of GaN-based semiconductors havestimulated a great deal of interest in research and developmentregarding nitride materials growth and optoelectronic andnitride-based electronic devices. High electron mobility andsaturation velocity, high sheet carrier concentration atheterojunction interfaces, high breakdown field, and low thermalimpedance of GaN-based films grown over SiC or bulk AlN substratesmake nitride-based electronic devices very promising.
Author: Fatima Husna
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Category :
Languages : en
Pages : 206
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Author: Joseph Record
Publisher:
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Category :
Languages : en
Pages : 96
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This thesis presents the fabrication, characterization, and off-state gate leakage simulation of Al x Ga 1−x N/GaN Heterojunction Field-Effect Transistors (HFETs). GaN HFETs are promising devices for high power, high frequency applications such as microwave amplifiers. This is due to the numerous benefits of the GaN material system including high electron mobility, breakdown field, saturation velocity, and thermal conductivity. This thesis is broken down into two major components. The first and most significant covers the fabrication and characterization of Al x Ga 1−x N/GaN HFETs. Devices were fabricated at McGill University’s Nanotools Microfabrication laboratory using a custom designed process flow. This process flow builds on previous work and presents Ohmic contact results of Ti/Al/Ti/Au and Ti/Al/Ti/Al/Ti/Au metalizations. A complete description of the process flow is provided including technology characterization results, such as mesa height profiling, where applicable. Electrical characterization of fabricated devices is performed. Results show an average contact resistance across temperature of 3.39Ωmm for the Ti/Al/Ti/Au metalization and 3.22Ωmm for the Ti/Al/Ti/Al/Ti/Au metalization. Full contact resistance results are provided over a wide range of temperature. The Ti-Al multi-layer metalization also outperforms the Ti/Al/Ti/Au metalization in terms of drain current density ( 0.12A/mm vs. 0.09A/mm ) and transconductance ( 60mS/mm vs. 40mS/mm ). Off-state gate leakage and current-voltage profiling are also carried out. The second part of this thesis concerns gate leakage current in Al x Ga 1−x N/GaN HFETs. A new off-state gate leakage model is presented to determine the variation in leakage mechanisms with the change in barrier layer aluminum mole fraction. A new metric of turning point is introduced to show where Fowler-Nordheim tunneling becomes the dominant leakage mechanism. Results show that as Al mole fraction is increased, the turning point becomes more negative and total gate leakage increases. Finally, improvements to the fabrication process and simulations are presented.
Author: Michael Shur
Publisher: World Scientific
ISBN: 9812388443
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: Momčilo Pejović
Publisher: BoD – Books on Demand
ISBN: 9535131753
Category : Technology & Engineering
Languages : en
Pages : 194
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In 1959, Atalla and Kahng at Bell Labs produced the first successful field-effect transistor (FET), which had been long anticipated by other researchers by overcoming the "surface states" that blocked electric fields from penetrating into the semiconductor material. Very quickly, they became the fundamental basis of digital electronic circuits. Up to this point, there are more than 20 different types of field-effect transistors that are incorporated in various applications found in everyday's life. Based on this fact, this book was designed to overview some of the concepts regarding FETs that are currently used as well as some concepts that are still being developed.
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Category :
Languages : en
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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.
