Toward III-nitride Based Ferroelectric High Electron Mobility Transistors PDF Download
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Author: Hyunjea Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
With growing needs for data-centric applications such as edge intelligence in recent years, the semiconductor industry has been actively looking for new computing hardware that involves high-speed and energy-efficient data processing solutions. Innovation in memory is critical in resolving the speed mismatch between memory and logic present in von Neumann-based computing architectures. Moving toward near-memory or in-memory computing architectures, which enable efficient data transfer between logic cores and memories, embedded non-volatile memories are arising as a strong candidate for dataintensive applications. In this work, ferroelectric field-effect transistors (FeFETs) are investigated as a memory element for such new computing platforms. The recent discovery of a ferroelectric nitride, ScAlN, shed light on the epitaxial nitride-based FeFET solution. Possessing several advantages for FeFET-based memories, ScAlN has the potential to outperform the widely-investigated Hf0.5Zr0.5O2. The MBE-grown ScAlN exhibits ferroelectric properties that are highly desirable for achieving a sufficient memory window at reasonable operating voltages. The high-quality epitaxial interfaces are expected to help mitigate charge trapping issues reported in Hf0.5Zr0.5O2-based FeFETs. This work aims to manifest the advantages of ScAlN for FeFETs compared with other ferroelectric options and to demonstrate experimental efforts toward the III-nitride FeFETs. An Analytical FeFET model is used to simulate and compare the figures of merit of FeFETs based on various ferroelectrics. ScAlN, grown by reactive co-sputtering and MBE, is fabricated into capacitors and field-effect transistors (FETs), and the electrical properties of the devices are investigated. Despite some challenges in the growth and fabrication of the recent generation, ScAlN shows the potential as a high-k dielectric barrier for FETs and is expected to add a ferroelectric functionality to the III-nitride platform.
Author: Hyunjea Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
With growing needs for data-centric applications such as edge intelligence in recent years, the semiconductor industry has been actively looking for new computing hardware that involves high-speed and energy-efficient data processing solutions. Innovation in memory is critical in resolving the speed mismatch between memory and logic present in von Neumann-based computing architectures. Moving toward near-memory or in-memory computing architectures, which enable efficient data transfer between logic cores and memories, embedded non-volatile memories are arising as a strong candidate for dataintensive applications. In this work, ferroelectric field-effect transistors (FeFETs) are investigated as a memory element for such new computing platforms. The recent discovery of a ferroelectric nitride, ScAlN, shed light on the epitaxial nitride-based FeFET solution. Possessing several advantages for FeFET-based memories, ScAlN has the potential to outperform the widely-investigated Hf0.5Zr0.5O2. The MBE-grown ScAlN exhibits ferroelectric properties that are highly desirable for achieving a sufficient memory window at reasonable operating voltages. The high-quality epitaxial interfaces are expected to help mitigate charge trapping issues reported in Hf0.5Zr0.5O2-based FeFETs. This work aims to manifest the advantages of ScAlN for FeFETs compared with other ferroelectric options and to demonstrate experimental efforts toward the III-nitride FeFETs. An Analytical FeFET model is used to simulate and compare the figures of merit of FeFETs based on various ferroelectrics. ScAlN, grown by reactive co-sputtering and MBE, is fabricated into capacitors and field-effect transistors (FETs), and the electrical properties of the devices are investigated. Despite some challenges in the growth and fabrication of the recent generation, ScAlN shows the potential as a high-k dielectric barrier for FETs and is expected to add a ferroelectric functionality to the III-nitride platform.
Author: Hansheng Ye
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Simon Fichtner
Publisher: BoD – Books on Demand
ISBN: 3750431426
Category : Science
Languages : en
Pages : 180
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Book Description
The usage of piezoelectric and ferroelectric thin films is a promising approach to significantly increase the functionality of microelectromechanical systems (MEMS) as well as of microelectronics in general. Since the device performance thus becomes directly connected to the properties of the functional film, new as well as improved piezoelectric and ferroelectric materials can allow substantial technological innovation. This dissertation focused on enhancing the piezoelectric properties of AlN by forming solid solutions with ScN and includes the first experimental observation of ferroelectricity in AlScN, and thus the first discovery of ferroelectricity in a III-V semiconductor based material in general. Compared to AlN, piezoelectric coefficients that are up to 450% higher were realized in AlScN, with d33f reaching a maximum of 17.2 pm/V and e31f reaching 3.2 C/m2. In this context, the identification and subsequent rectification of a major morphological instability in AlScN that becomes more pronounced with increasing Sc content was reported. Thus, films free of morphological inhomogeneities with close to ideal piezoelectric properties could be deposited up to 0.43% ScN. Control of the intrinsic film stress was demonstrated over a wide range from strongly tensile to strongly compressive for all the investigated Sc contents. The improved piezoelectric coefficients together with the possibility of stress control allowed the fabrication of suspended MEMS structures with electromechanical coupling coefficients improved by more than 320% relative to AlN. Ferroelectrictiy in AlScN was observed starting at ScN contents of 27%. Its emergence was connected to the same gradual evolution from the initial wurtzite structure to the layered hexagonal structure that also causes the enhanced piezoelectric coefficients while increasing the Sc content. Ferroelectric AlScN allowed the first experimental observation of the spontaneous polarization of the wurtzite structure and confirms that this polarization is more than one order of magnitude above most previous theoretical predictions. The large, tunable coercive fields and polarization constants together with the broad linear strain intervals, a paraelectric transition temperature above 600°C as well as the technological compatibility of the III-nitrides lead to a combination of exceptional properties that was previously inaccessible in ferroelectric thin films.
Author: D. Nirmal
Publisher: CRC Press
ISBN: 0429862520
Category : Science
Languages : en
Pages : 446
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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: Lars Heuken
Publisher:
ISBN: 9783844077162
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al.sub.y Ga.sub. 1-y N (y=1 or y 1) layer on the GaN buffer layer. An Al.sub.x Ga.sub. 1-x N (0.ltoreq.x.ltoreq.0.5) barrier layer on to the Al.sub.y Ga.sub. 1-y N layer, opposite the GaN buffer layer, Al.sub.y Ga.sub. 1-y N layer having a higher Al concentration than that of the Al.sub.x Ga.sub. 1-x N barrier layer. A preferred Al.sub.y Ga.sub. 1-y N layer has y=1 or y.about. 1 and a preferred Al.sub.x Ga.sub. 1-x N barrier layer has 0.ltoreq.x.ltoreq.0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al.sub.y Ga.sub. 1-y N layer. Respective source, drain and gate contacts are formed on the Al.sub.x Ga.sub. 1-x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al.sub.y Ga.sub. 1-y N layer and a nucleation layer between the Al.sub.x Ga.sub. 1-x N buffer layer and the substrate.
Author: Fabrizio Roccaforte
Publisher: John Wiley & Sons
ISBN: 3527825258
Category : Technology & Engineering
Languages : en
Pages : 464
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Book Description
The book "Nitride Semiconductor Technology" provides an overview of nitride semiconductors and their uses in optoelectronics and power electronics devices. It explains the physical properties of those materials as well as their growth methods. Their applications in high electron mobility transistors, vertical power devices, LEDs, laser diodes, and vertical-cavity surface-emitting lasers are discussed in detail. The book further examines reliability issues in these materials and puts forward perspectives of integrating them with 2D materials for novel high-frequency and high-power devices. In summary, it covers nitride semiconductor technology from materials to devices and provides the basis for further research.
Author: Vinod Ravindran
Publisher:
ISBN:
Category : Boron
Languages : en
Pages :
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Book Description
GaN-based HEMTs are among the most promising candidates for high-power and high-frequency applications; a niche for millimeter-wave technologies. Nitride materials indeed outperform other mainstream III-V materials (InP or GaAs) because of several properties, including wider bandgaps, high peak and saturation velocities, large breakdown voltages, together with good thermal conductivities. Nonetheless, the state-of-the-art of nitrides is not yet industrially mature to exploit the entire millimeter-wave range. A way to push further performance is to develop innovative designs, notably by exploring novel materials. The purpose of this research was therefore to investigate the use of boron-containing III-nitrides in high electron mobility transistors (HEMTs). The study was first conducted theoretically, through solving the Schrodinger-Poisson equation. Key parameters and relevant equations were derived to implement BGaN materials in our simulations. A GaN/ultrathin-BGaN/GaN heterojunction was showed to provide an electrostatic barrier to electrons and to improve the confinement of the two-dimensional electron gas. GaN back-barrier layers happen to limit leakage in the GaN buffer thanks to two effects: (i) a polarization-induced band discontinuity and (ii) a resistive barrier originating from excellent insulation properties of BGaN. The study was then, experimentally, several growth campaigns were carried out that led to the fabrication of devices. First, we confirmed the key characteristics of BGaN materials by electrical and optical measurements. Second, we demonstrated the evidence of a significant enhancement of performance of standard AlGaN/GaN structures by the introduction of a BGaN layer in the buffer layer. Compared to conventional AlGaN/GaN HEMTs, structures grown with BGaN back-barriers showed a significant improvement of static performances, transport properties, and trapping effects involving a limited current collapse in dynamic regime.
Author: Zhichao Yang
Publisher:
ISBN:
Category : Electrons
Languages : en
Pages : 83
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Book Description
GaN high electron mobility transistors (HEMTs) have the ability to deliver high power density for high frequency applications. Lateral scaling and Ohmic contact regrowth has enabled high cutoff (fT) and maximum oscillation frequency (fmax) demonstrations. However, the frequency and power density of lateral HEMTs face some fundamental physical limits. To achieve amplification at higher frequency, the power gain at high frequency needs to be increased by reducing transit and RC delays, while maintaining low output conductance. In lateral structures, reducing the transit delay, which is done by shrinking lateral dimensions, also leads to an increase in the output conductance, which degrades high frequency power gain. In addition, in the systems with highly scaled 2D electron gases such as AlGaN/GaN HEMTs, the energy dissipation in a thin sheet-like volume leads to significant local heating and temperature rise. In this proposal, we investigate vertical transistors based on hot electron transport - tunneling hot electron transistor (THETA). As compared to lateral transport, electron transport can be defined by heterojunction growth at a scale shorter than 10 nm, and output conductance can be controlled through doping and epitaxial engineering. Furthermore, the power dissipation in a vertical device occurs over a volume rather than in a 2D sheet, the local temperature rise is not as significant as in the lateral case. THETA had been previously demonstrated in GaAs systems, and current gain in excess of 10 had been achieved with wide-bandgap AlSbAs emitter at room temperature. GaN THETA has been reported in recent years but the current gain in these devices has remained relatively low. We demonstrate GaN THETA operating with common-emitter current gain above 10 for the first time by implementing polarization engineered barriers in the emitter-base and base-collector junctions. Additionally, the III-Nitride system offers a significantly different way of engineering high fields in a semiconductor even without geometrical field enhancement and enables highly-energetic hot electron transport to ballistically emit electrons. Therefore, high efficiency and current density hot electron emitters can be achieved in III-Nitride. For future work, we will optimize the design and reduce the junction leakage to improve the injection efficiency of the hot electrons. For fabrication, we will use advanced processing technology such as e-beam lithography to define highly-scaled THETA for high-frequency.
Author: Pil Sung Park
Publisher:
ISBN:
Category :
Languages : en
Pages : 159
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Book Description
Abstract: In this thesis, we have investigated and overcome the major limiting factors of intrinsic and parasitic parameters in III-Nitride high electron mobility transistors for high frequency performance with a combined study of simulations and experimental work. The high frequency RF performance of these transistors is severely degraded when short-channel effects, and parasitic resistances are present. To investigate short-channel effects, first, we have developed a simulation model for Ga-polar and N-polar HEMT structures, and found the main reasons for these degradations are drain-induced barrier-lowering and space-charge-limited current injection. To mitigate this, a strong electrostatic back-barrier structure from N-polar orientation is suggested. Secondly, the effect of quantum displacement in GaN HEMTs were investigated using both simulation and experimental measurements. It was discovered that the quantum displacement in a highly scaled device can give more than 2x change in the gate-source capacitance between two different orientations. Therefore it is imperative that the device design for such highly scaled devices consider quantum displacement effects in order to avoid short-channel effects. Another limiting factor from extrinsic elements is the parasitic resistances, especially from contact resistance. To achieve low-resistance non-alloyed Ohmic contacts, we developed two new process technologies that included an inserted graphene layer between metal and AlGaN, and a graded n+ AlGaN Ohmic layer. Both approaches utilized the current path where no barrier exists. In this work, we set the record low contact resistance of 0.049 Ohm mm for Ga-polar technology using the graded AlGaN scheme. The most crucial factor for improving high frequency performance for III-Nitride HEMTs is the saturation of the effective electron velocity. We have modeled the velocity saturation in GaN channel based on LO phonon emission, and explain the phenomena of rapidly decreasing behavior transconductance. This model was also applied to 2-D device simulation where it was possible to obtain the DC and RF characteristics matching to the experimental results. To overcome the fast reduction in gm and fT, we have introduced a polarization graded channel in AlGaN/GaN HEMT and graded AlGaN HFET to tailor the charge profile, and demonstrated a flat gm profile for the first time in field-effect-transistor structure. The high frequency performance of this engineered channel was measured from a highly scaled graded AlGaN HFET with advanced process technology including contact layer regrowth and e-beam lithography. Although the flat gm improved the linearity of fT and fmax, they do not stay flat due to an increasing capacitance profile in a regular 2 X 50 micrometre device. With further scaling of the device width, we obtained an increasing gm profile which can compensate the increment of capacitance, and finally we demonstrated flat fT and fmax profile which has been unseen in any field-effect-transistors. All these results shown in this thesis can contribute to further improvements in high frequency and high power performance of III-Nitride HEMTs for the future RF application beyond mm-Wave frequency.
