The Role of Defects on Schottky and Ohmic Contact Characteristics for GaN and AlGaN/GaN High-electron Mobility Transistors PDF Download
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Author: Dennis Eugene Walker
Publisher:
ISBN:
Category : Cathodoluminescence
Languages : en
Pages : 217
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Book Description
Abstract: The AlGaN/GaN material system is ideally suited for UV detectors, light sources, and high performance, high power transistors. Through an understanding of the physics and device properties associated with defects, engineered solutions can allow the utilization of the full potential of AlGaN/GaN device properties. Auger Electron Spectroscopy (AES) and secondary electron threshold (SET) techniques allow the characterization of band bending and work function at semiconductor surfaces. Using these techniques with ultra-high vacuum (UHV) sample cleaving and metal deposition, Schottky barrier formation to non-polar GaN was investigated revealing cases of both ideal band-bending and Fermi level pinning. Cathodoluminescence spectroscopy (CL) allows the investigation of luminescent defect levels with depth-resolving capability by controlling the incident beam voltage and associated electron beam penetration into the sample. High electron mobility transistors (HEMTs) exhibiting current collapse were investigated using CL and CL mapping and specific defects were found in the GaN channel and buffer regions that may help explain the current collapse phenomena. Coupling a novel gate mask into a typical HEMT fabrication sequence and utilizing three, independent UHV sample cleaning techniques including thermal desorption of contaminants, Ga-reflux, and N2 ion sputtering, and metallization of the gates on AlGaN/GaN HEMTs, correlations in defect levels, surface cleaning technique, and finished device performance were found. In analyzing the CL data for this sample, however, a specific feature located just below the GaN near band edge was observed to accumulate near the Ohmic contacts prompting a further investigation of both the effects of the RIE etch used in producing the UHV-compatible mask as well as four different Ohmic contact structures on both defect levels determined by CL and on final device performance. Finally, a bulk GaN sample was processed with Ohmic contacts to determine the correlation of the AlGaN device layer in the formation of this defect level associated with the Ohmic contacts and the role of the mesa RIE etch on the same defect. Through these investigations, progress in the underlying physics of Schottky barrier formation on GaN and the important role of defects on device performance using AES, SET, and CL have been demonstrated.
Author: Dennis Eugene Walker
Publisher:
ISBN:
Category : Cathodoluminescence
Languages : en
Pages : 217
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Book Description
Abstract: The AlGaN/GaN material system is ideally suited for UV detectors, light sources, and high performance, high power transistors. Through an understanding of the physics and device properties associated with defects, engineered solutions can allow the utilization of the full potential of AlGaN/GaN device properties. Auger Electron Spectroscopy (AES) and secondary electron threshold (SET) techniques allow the characterization of band bending and work function at semiconductor surfaces. Using these techniques with ultra-high vacuum (UHV) sample cleaving and metal deposition, Schottky barrier formation to non-polar GaN was investigated revealing cases of both ideal band-bending and Fermi level pinning. Cathodoluminescence spectroscopy (CL) allows the investigation of luminescent defect levels with depth-resolving capability by controlling the incident beam voltage and associated electron beam penetration into the sample. High electron mobility transistors (HEMTs) exhibiting current collapse were investigated using CL and CL mapping and specific defects were found in the GaN channel and buffer regions that may help explain the current collapse phenomena. Coupling a novel gate mask into a typical HEMT fabrication sequence and utilizing three, independent UHV sample cleaning techniques including thermal desorption of contaminants, Ga-reflux, and N2 ion sputtering, and metallization of the gates on AlGaN/GaN HEMTs, correlations in defect levels, surface cleaning technique, and finished device performance were found. In analyzing the CL data for this sample, however, a specific feature located just below the GaN near band edge was observed to accumulate near the Ohmic contacts prompting a further investigation of both the effects of the RIE etch used in producing the UHV-compatible mask as well as four different Ohmic contact structures on both defect levels determined by CL and on final device performance. Finally, a bulk GaN sample was processed with Ohmic contacts to determine the correlation of the AlGaN device layer in the formation of this defect level associated with the Ohmic contacts and the role of the mesa RIE etch on the same defect. Through these investigations, progress in the underlying physics of Schottky barrier formation on GaN and the important role of defects on device performance using AES, SET, and CL have been demonstrated.
Author: Benedict C. Ofuonye
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
High work function metals--Ni, Pt, Ir, and Au--were comparatively studied as Schottky metallizations to GaN and AlGaN/GaN heterostructures. Ni/Au, Ni/Pt/Au, Ir/Au, Ir/Pt/Au and Pt/Au Schottky diodes were fabricated on GaN and AlGaN/GaN substrates. Schottky barrier heights ranging from 0.8 to 0.9 eV were obtained as-deposited on GaN with ideality factors of about 1.05. The quality of the Schottky diodes was evaluated and their thermal stability also was studied. The interposition of Pt in Ni/Au and Ir/Au systems was found to improve the characteristics of the Schottky diodes. Ir/Pt/Au diodes were found to be more thermally stable than Ni/Pt/Au diodes. Ni/Au Schottky contacts exhibited good leakage response under thermal annealing for long periods. Microstructural studies were carried out on Ni/Pt/Au and Ni/Au Schottky contacts to elucidate the role of the intermediate layer, Pt, in the degradation of the Ni/Pt/Au metallization under long-term thermal anneal. A selective-area silicon ion implantation process for ohmic contact resistance improvement to AlGaN/GaN high electron mobility transistors (HEMTs) was developed. Non-alloyed ohmic contacts with very low contact resistances of 0.2 - 0.24 -mm were achieved with TLM pads fabricated using the Mo/Al/Mo/Au metallization. Simulations were carried out with SRIM to qualify the implantation process. Surface chemistry analysis was undertaken on the implanted AlGaN/GaN and GaN samples to determine the impact of implantation on the surface morphology of the AlGaN layer. The developed ion-implantation process was used to propose fabrication schemes for novel high speed self-aligned and non-self-aligned AlGaN/GaN high electron mobility trasistors (HEMTs) employing Ir/Pt/Au or Ni/Au gate and non-alloyed ohmic contact metallizations.
Author: D. Nirmal
Publisher: CRC Press
ISBN: 0429862539
Category : Science
Languages : en
Pages : 430
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Book Description
This book focusses on III-V high electron mobility transistors (HEMTs) including basic physics, material used, fabrications details, modeling, simulation, and other important aspects. It initiates by describing principle of operation, material systems and material technologies followed by description of the structure, I-V characteristics, modeling of DC and RF parameters of AlGaN/GaN HEMTs. The book also provides information about source/drain engineering, gate engineering and channel engineering techniques used to improve the DC-RF and breakdown performance of HEMTs. Finally, the book also highlights the importance of metal oxide semiconductor high electron mobility transistors (MOS-HEMT). Key Features Combines III-As/P/N HEMTs with reliability and current status in single volume Includes AC/DC modelling and (sub)millimeter wave devices with reliability analysis Covers all theoretical and experimental aspects of HEMTs Discusses AlGaN/GaN transistors Presents DC, RF and breakdown characteristics of HEMTs on various material systems using graphs and plots
Author: Monta Raymond Holzworth (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
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Book Description
AlGaN/GaN high electron mobility transistors are unique for their combination of high temperature, high power, and high frequency applications. Compared to Si, Ge, and compound semiconductors such as GaAS and InP, AlGaN/GaN transistors outclass the current technology due to their superior combination of high breakdown voltage and high frequency performance. These characteristics arise from structural and electrical properties inherent to the AlGaN/GaN heterojunction which have enabled AlGaN/GaN transistors usage in important military and civilian applications such as microwave and millimeter technology, RADAR systems, and as high current and voltage switches in utility grid systems. As the technology continues to improve due to increased materials quality and device advancements, future applications will require AlGaN/GaN transistor usage under even higher voltages and temperatures. Therefore, the effects of these stresses need to be investigated in order improve device performance and reliability.
Author: Hongyu Yu
Publisher: CRC Press
ISBN: 1351767615
Category : Science
Languages : en
Pages : 298
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Book Description
GaN is considered the most promising material candidate in next-generation power device applications, owing to its unique material properties, for example, bandgap, high breakdown field, and high electron mobility. Therefore, GaN power device technologies are listed as the top priority to be developed in many countries, including the United States, the European Union, Japan, and China. This book presents a comprehensive overview of GaN power device technologies, for example, material growth, property analysis, device structure design, fabrication process, reliability, failure analysis, and packaging. It provides useful information to both students and researchers in academic and related industries working on GaN power devices. GaN wafer growth technology is from Enkris Semiconductor, currently one of the leading players in commercial GaN wafers. Chapters 3 and 7, on the GaN transistor fabrication process and GaN vertical power devices, are edited by Dr. Zhihong Liu, who has been working on GaN devices for more than ten years. Chapters 2 and 5, on the characteristics of polarization effects and the original demonstration of AlGaN/GaN heterojunction field-effect transistors, are written by researchers from Southwest Jiaotong University. Chapters 6, 8, and 9, on surface passivation, reliability, and package technologies, are edited by a group of researchers from the Southern University of Science and Technology of China.
Author: Chung-Han Lin
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Our DRCLS, SPS, time-resolved SPS (t-SPS), current-voltage-temperature (I-V-T) shows that fast and thermal neutron preferentially affect device properties. Fast neutron will induce defects in GaN by recoil and displacement damage whereas thermal neutron tends to enhance the interaction between metal/semiconductor interfaces due to heat. Time-resolved surface photovoltage spectroscopy (t-SPS) results reveal a defect evolution of GaN under fast neutron irradiation that indicates low fast neutron dosage will enhance GaN properties a result which is confirmed by DRCLS results. XPS results show that Ti and Ni are more resistant than other metal but will interact with GaN at higher thermal neutron fluence. Our results show that fast and thermal neutrons are both detrimental electronic devices without proper protection.
Author: Yue Hao
Publisher: CRC Press
ISBN: 149874513X
Category : Computers
Languages : en
Pages : 389
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Book Description
This book systematically introduces physical characteristics and implementations of III-nitride wide bandgap semiconductor materials and electronic devices, with an emphasis on high-electron-mobility transistors (HEMTs). The properties of nitride semiconductors make the material very suitable for electronic devices used in microwave power amplification, high-voltage switches, and high-speed digital integrated circuits.
Author: Matteo Meneghini
Publisher: Springer
ISBN: 3319431994
Category : Technology & Engineering
Languages : en
Pages : 383
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Book Description
This book presents the first comprehensive overview of the properties and fabrication methods of GaN-based power transistors, with contributions from the most active research groups in the field. It describes how gallium nitride has emerged as an excellent material for the fabrication of power transistors; thanks to the high energy gap, high breakdown field, and saturation velocity of GaN, these devices can reach breakdown voltages beyond the kV range, and very high switching frequencies, thus being suitable for application in power conversion systems. Based on GaN, switching-mode power converters with efficiency in excess of 99 % have been already demonstrated, thus clearing the way for massive adoption of GaN transistors in the power conversion market. This is expected to have important advantages at both the environmental and economic level, since power conversion losses account for 10 % of global electricity consumption. The first part of the book describes the properties and advantages of gallium nitride compared to conventional semiconductor materials. The second part of the book describes the techniques used for device fabrication, and the methods for GaN-on-Silicon mass production. Specific attention is paid to the three most advanced device structures: lateral transistors, vertical power devices, and nanowire-based HEMTs. Other relevant topics covered by the book are the strategies for normally-off operation, and the problems related to device reliability. The last chapter reviews the switching characteristics of GaN HEMTs based on a systems level approach. This book is a unique reference for people working in the materials, device and power electronics fields; it provides interdisciplinary information on material growth, device fabrication, reliability issues and circuit-level switching investigation.
Author: Yun-Ju Sun
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Book Description
Author: Hari Singh Nalwa
Publisher: Elsevier
ISBN: 0080533248
Category : Technology & Engineering
Languages : en
Pages : 3436
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Book Description
This five-volume handbook focuses on processing techniques, characterization methods, and physical properties of thin films (thin layers of insulating, conducting, or semiconductor material). The editor has composed five separate, thematic volumes on thin films of metals, semimetals, glasses, ceramics, alloys, organics, diamonds, graphites, porous materials, noncrystalline solids, supramolecules, polymers, copolymers, biopolymers, composites, blends, activated carbons, intermetallics, chalcogenides, dyes, pigments, nanostructured materials, biomaterials, inorganic/polymer composites, organoceramics, metallocenes, disordered systems, liquid crystals, quasicrystals, and layered structures.Thin films is a field of the utmost importance in today's materials science, electrical engineering and applied solid state physics; with both research and industrial applications in microelectronics, computer manufacturing, and physical devices.Advanced, high-performance computers, high-definition TV, digital camcorders, sensitive broadband imaging systems, flat-panel displays, robotic systems, and medical electronics and diagnostics are but a few examples of miniaturized device technologies that depend the utilization of thin film materials. The Handbook of Thin Films Materials is a comprehensive reference focusing on processing techniques, characterization methods, and physical properties of these thin film materials.
