Daxin Han

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Han

First Name

Daxin

ORCID

0000-0002-0301-5211

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Publications1 - 10 of 18

Low-Noise Microwave Performance of 30 nm GaInAs MOS-HEMTs: Comparison to Low-Noise HEMTs
Han, Daxin; Calvo Ruiz, Diego; Bonomo, Giorgio; et al. (2020)
IEEE Electron Device Letters
GaInAs-based Metal Oxide Semiconductor High Electron Mobility Transistors (MOS-HEMTs) can in principle combine the wide bandwidth of HEMTs to the low gate leakage current of MOSFETs in a single deeply-scaled ultrahigh speed low-noise technology. Despite advances in the fabrication of MOS-HEMT devices and MMICs, the transistor microwave noise properties of GaInAs MOS-HEMT devices have not yet been reported. In the present study, the room temperature DC and wideband RF noise properties (8-50 GHz) of GaInAs channel MOS-HEMTs are characterized and contrasted to those of a 50 nm low-noise HEMT with the same channel composition/thickness and similar fT: at a given bias VDS = 0.5 V, the HEMT provides lower minimal noise figures (NFMIN) and higher associated gain. In contrast to HEMTs, the MOS-HEMTs particularly suffer from lower frequency noise contributions attributed to enhanced impact ionization. Remarkably, operation at VDS = 0.4 V to mitigate ionization enables MOS-HEMTs to match the HEMT wideband NFMIN performance despite a significantly poorer low-field channel mobility. The present MOS-HEMTs show the highest reported maximum oscillation frequency fMAX = 637 GHz for a measured gate length LG = 33 nm and a (2 × 15) μm width. Gate annealing is shown to be deleterious to the MOS-HEMT DC and noise properties.
InP-Based High-Speed Metal Oxide Semiconductor Transistors
Han, Daxin (2022)
The Metal oxide semiconductor field effect transistor (MOSFET) is widely implemented in both digital and analog applications, benefiting many aspects of our daily lives. Due to the increase in the transistor subthreshold operation static power consumption, traditional silicon MOSFETs are facing challenges in keeping their scaling pace in digital circuits. III-V narrow gap buried channel MOSFETs with ALD Al2O3 as gate oxide feature a strong impact ionization effect, causing steep subthreshold operation with subthreshold slope (SS) far below the Boltzmann limitation. Such InP-based MOSFETs are for digital circuits operated at higher clock frequency while maintaining a low level of power dissipation. At the same time, the growing demand for analog circuits operating at higher frequency bands is also driving the transition from silicon channel transistors to III V narrow gap buried channel transistors. These III-V MOSFETs have shown transconductance and cutoff frequencies competitive with those of HEMTs using similar channels, but the III-V MOSFETs have not yet been investigated in terms of microwave noise performance up to now. In order to investigate the steep-slope switching capability of the III-V MOSFETs for digital applications, InP-based MOSFETs were developed using a buried narrow gap channel and ALD Al2O3 as a gate oxide. Both n-type MOSFETs with GaInAs channel and p-type MOSFETs with GaAsSb channel were epitaxially grown and fabricated. The GaInAs n-MOSFETs showed an SS well below Boltzmann limitation over a wide range of drain current, and they exhibited a digital switching time of less than 20 picoseconds as well as high analog cutoff frequencies. Moreover, the n-MOSFETs with InAs insets in their GaInAs channels achieved low SS with sub-volt drain bias. These n-MOSFETs, featuring both robust steep slope effect and high-speed analog/digital capabilities, offer a relatively simple technology platform for the realization of mixed-mode analog/digital circuits. In addition, GaAsSb p-MOSFETs were also fabricated and showed an SS below Boltzmann limitation over a wide range of drain current modulation, potentially providing an I-CMOS logic platform in integration with the n-MOSFETs. Moreover, to evaluate the feasibility of implementing III-V MOSFETs in high frequency analog applications, GaInAs buried channel MOSFETs (also referred to as MOS HEMTs) were developed and characterized for their DC and RF properties. These MOSFETs have subchannel δ doping and ALD Al2O3 gate oxide. They exhibited a record high maximum oscillation frequency among III V MOSFETs with a similar channel design. With slightly reduced drain bias to mitigate the impact ionization, the MOSFETs were able to match the wideband noise performance of a standard GaInAs HEMT consisting of the same channel over 8 to 50 GHz.
Effects of Electrochemical Etching on InP HEMT Fabrication
Saranovac, Tamara; Ruiz, Diego C.; Han, Daxin; et al. (2019)
IEEE Transactions on Semiconductor Manufacturing
Nanocellulose Assisted Preparation of Ambient Dried, Large-Scale and Mechanically Robust Carbon Nanotube Foams for Electromagnetic Interference Shielding
Zeng, Zhihui; Wang, Changxian; Wu, Tingting; et al. (2020)
Journal of Materials Chemistry A
Nanofibrillated cellulose is efficiently employed as a green dispersant, cross-linker and structure-directing agent assisting in the preparation of large-area ambient pressure dried carbon nanotube (CNT) foams using a facile, energy-efficient, and scalable freezing–thawing–drying approach. The resultant CNT based foams show unidirectional microhoneycomb pore channels, high mechanical strength, good conductivity, controllable wide-ranging densities, and functional attributes of high-efficiency organic dye absorption and designed hydrophobicity. The significant pore microchannel orientation allows for a facile tuning of the electromagnetic interference (EMI) shielding performances of the CNT foams. This is demonstrated by efficiently controlling the angle of the pore orientation with respect to the electric field direction of the incident electromagnetic waves. Combining the adept controllability of the building blocks and the excellent EMI shielding effectiveness (SE) of more than 70 dB, resulting in a specific SE of up to 6111 dB cm2 g−1, our work shows the great potential of these air-dried nanostructured cellular monoliths in EMI shielding applications.
High-Speed Steep-Slope GaInAs Impact Ionization MOSFETs (I-MOS) With SS = 1.25 mV/dec - Part I: Material and Device Characterization, DC Performance, and Simulation
Han, Daxin; Bonomo, Giorgio; Calvo Ruiz, Diego; et al. (2022)
IEEE Transactions on Electron Devices
Digital electronics power consumption evolved into a major concern: at the current pace, general-purpose computing energy consumption will exceed global energy production before 2045. The principal approach to curbing energy consumption in digital applications calls for ``steep-slope'' devices with an inverse subthreshold slope (SS) parameter well below the ``ln(10)·kT/q'' limit of conventional electronics (60 mV/dec at 300 K). Impact ionization MOSFETs (I-MOS) provide an avenue for steep-slope device realization. High-mobility narrow gap III-V semiconductor channel materials have not yet been investigated for I-MOS applications. We hereby report E-mode narrow bandgap GaInAs-based I-MOS devices with an SS of 1.25 mV/dec maintained over five orders of magnitude in drain current and Ion / Ioff ratios >10⁶ at 300 K (>10⁹ at 15 K) for a gate length of LG = 100 nm. Part I of this work focuses on the materials and device fabrication and analysis, device dc characterization, and modeling. The present GaInAs devices are the first I-MOS transistors to display a robust steep-slope effect at low voltages VDS < 1.9 V at 300 K and <1 V at 15 K. Part II describes the dynamic switching (including clarifications on the role of hysteresis) and RF characteristics of GaInAs I-MOS devices and benchmarks them with respect to other steep-slope technologies.
Ultrafine Cellulose Nanofiber‐Assisted Physical and Chemical Cross‐Linking of MXene Sheets for Electromagnetic Interference Shielding
Wu, Na; Zeng, Zhihui; Kummer, Nico; et al. (2021)
Small Methods
Transition metal carbides and nitrides (MXenes) have shown great potential for constructing thin, high-performance electromagnetic interference (EMI) shields. The challenges with these materials involve the weak interfacial interactions of MXenes, which results in inferior mechanical properties and structure of the MXene films and a conductivity/EMI shielding performance decay related to the poor MXene oxidation stability. Numerous efforts have been devoted to improving the mechanical properties or oxidation stability of the films, which always comes at the expense of EMI shielding performance. Here, ultrafine (≈1.4 nm) cellulose nanofibers are employed to achieve physical and chemical dual cross-linking of MXene (PC-MXene) nanosheets. The procedure involves drying of flexible and highly conductive PC-MXene films at ambient pressure and is energy-efficient and scalable. Compared to the MXene films, the PC-MXene films show significantly improved mechanical strength, hydrophobicity, oxidation stability, and are waterproof, without compromising the excellent EMI shielding effectiveness (SE). Moreover, the freestanding PC-MXene films reach a thickness of merely 0.9 µm and exhibit a high SE of 33.3 dB, which cannot be achieved by pure MXene films. This leads to ultrahigh thickness-specific SE and surface-specific SE values of 37 000 dB mm−1 and 148 000 dB cm2 g−1 respectively, significantly surpassing those of previously reported MXene-based films.
Impact Ionization Control in 50 nm Low-Noise High-Speed InP HEMTs with InAs Channel Insets
Ruiz, Diego C.; Saranovac, Tamara; Han, Daxin; et al. (2019)
2019 IEEE International Electron Devices Meeting (IEDM)
Impact ionization negatively affects transistor noise properties at low and mm-wave frequencies. We show that composite InAs/GaInAs channels with thin InP sub-channels can be engineered to greatly suppress impact ionization and achieve improved noise properties while maintaining excellent HEMTs cutoff frequencies (f(T)/f(MAX) > 410/660 GHz with L-G = 50 nm). This is the first demonstration of high-performance HEMTs combining InAs channel insets with InP sub-channels. HEMTs with a 3 nm InAs inset and an InP sub channel outperform designs relying on 5 nm InAs insets in f(T)/f(MAX) metrics at higher drain biases and currents, as well as in low-noise performance. At 40 GHz, the 3 nm InAs inset HEMT shows NFMIN = 0.65 dB (compared to 0.93 and 1.15 dB for the 5 nm InAs inset HEMTs, with and without InP sub-channel, respectively). We extract the "impact ionization transconductance" g(im) from S-parameter measurements to quantify and map impact ionization levels over the I-DS-V-DS domain for the first time, clearly showing a delayed onset to higher V-DS and I-DS values in the optimized channel design (3 nm InAs inset with an InP sub-channel).
Effects of Electrochemical Etching on InP HEMT Fabrication
Saranovac, Tamara; Calvo Ruiz, Diego; Han, Daxin; et al. (2019)
2019 International Conference on Compound Semiconductor MANufacturing TECHnology. Digest of Papers
InAs Channel Inset Effects on the DC, RF, and Noise Properties of InP pHEMTs
Calvo Ruiz, Diego; Saranovac, Tamara; Han, Daxin; et al. (2019)
IEEE Transactions on Electron Devices
High-Speed Steep-Slope GaInAs Impact Ionization MOSFETs (I-MOS) With SS = 1.25 mV/dec - Part II: Dynamic Switching and RF Performance
Han, Daxin; Bonomo, Giorgio; Calvo Ruiz, Diego; et al. (2022)
IEEE Transactions on Electron Devices
Part I of this work described narrow bandgap GaInAs-based I-MOS devices with a minimum steep slope SSmin = 1.25 mV/dec maintained over 4 orders of magnitude in drain current, ION/IOFF ratios >106 at 300 K (>109 at 15 K), and low operating voltages for a gate length of LG = 100 nm. Part II focuses on the device time-domain switching capabilities and RF performance. Digital switching tests using a hybrid connected inverter reveal excellent capabilities for high clock rate operation. Simple circuit estimates indicate that the present 100 nm GaInAs I-MOS can operate with clock frequencies >10 GHz. The impact-ionization-induced hysteresis in the ID – VGS I-MOS characteristics does not play any role in dynamic switching of a digital inverter: the n -channel pull-down transistor turns on with a steep slope, but turns off classically with a higher threshold voltage which reduces the dynamic power dissipation per switching cycle. Factors impacting GaInAs I-MOS reliability are considered, and a physically motivated approach to enhance the reliability of III–V MOSFETs is proposed. We show that GaInAs-based I-MOS devices offer high analog cutoff frequencies and low-noise characteristics, suggesting applicability for digital and RF applications on a single technological platform. When benchmarked against other steep-slope technologies, GaInAs I-MOS shows the strongest steep slope, competitive ION/IOFF ratios, and lowest operating voltage of any I-MOS transistor to date, without any back-gate/substrate bias.

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Daxin Han

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