| 1. |
- Dzhigaev, Dmitry, et al.
(författare)
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Strain mapping inside an individual processed vertical nanowire transistor using scanning X-ray nanodiffraction
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 12:27, s. 14487-14493
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires in wrapped, gate-all-around transistor geometry are highly favorable for future electronics. The advanced nanodevice processing results in strain due to the deposited dielectric and metal layers surrounding the nanowires, significantly affecting their performance. Therefore, non-destructive nanoscale characterization of complete devices is of utmost importance due to the small feature sizes and three-dimensional buried structure. Direct strain mapping inside heterostructured GaSb-InAs nanowire tunnel field-effect transistor embedded in dielectric HfO2, W metal gate layers, and an organic spacer is performed using fast scanning X-ray nanodiffraction. The effect of 10 nm W gate on a single embedded nanowire with segment diameters down to 40 nm is retrieved. The tensile strain values reach 0.26% in the p-type GaSb segment of the transistor. Supported by the finite element method simulation, we establish a connection between the Ar pressure used during the W layer deposition and the nanowire strain state. Thus, we can benchmark our models for further improvements in device engineering. Our study indicates, how the significant increase in X-ray brightness at 4th generation synchrotron, makes high-throughput measurements on realistic nanoelectronic devices viable.
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| 2. |
- Han, Yi, et al.
(författare)
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Abnormal strain in suspended GeSn microstructures
- 2018
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Ingår i: Materials Research Express. - : IOP Publishing. - 2053-1591. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- A suspended GeSn microstructure is realized by a two-step selective wet etching technique with the aim of fully relaxing the compressive strain, promoting the indirect to direct bandgap transition and improving the optical property of GeSn thin films grown on Ge. The compressive strain was found efficiently relaxed, and even unexpected large tensile strain was displayed on regions of the microstructure by micro-Raman spectroscopy. Residual Ge patches under the suspended GeSn microstructure were found by scanning electron microscopy and proved to be the origin of the tensile strain by finite element method simulations. The tensile strain on the surface is beneficial for direct bandgap conversion and carrier accumulation. Significant enhancement of photoluminescence was obtained in the GeSn microstructures than the original thin film.
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| 3. |
- Krishnaraja, Abinaya, et al.
(författare)
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Low-Power, Self-Aligned Vertical InGaAsSb NW PMOS With S < 100 mV/dec
- 2023
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 44:7, s. 1064-1067
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Tidskriftsartikel (refereegranskat)abstract
- III-V co-integration is less mature compared to Si/Ge CMOS due to their inferior pMOS device performance. This letter adopts a novel quaternary InGaAsSb channel material in a core-shell vertical nanowire structure to overcome the limitations. A gate-last process achieves self-alignment of the drain and gate contacts. The improved electrostatics with short gate length ${L}_{\text {g}}$ = 60 nm results in a good balance between the on-state and the off-state performances. The presented devices demonstrate the lowest inverse subthreshold slope ( ${S}$ ) for a III-V PMOS with ${S}_{\text {sat}}$ = 75 mV/dec with significant ${I}_{\text {on}}/{I}_{\text {off}}$ ratio of $10^{{4}}$ and ${I}_{\text {min}} < $ 1 nA/ $\mu \text{m}$. The substantial improvement in the device performance compared to earlier reports provides an opportunity for III-V complementary field-effect transistor integration.
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| 4. |
- Krishnaraja, Abinaya, et al.
(författare)
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Tuning of Source Material for InAs/InGaAsSb/GaSb Application-Specific Vertical Nanowire Tunnel FETs
- 2020
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 2:9, s. 2882-2887
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Tidskriftsartikel (refereegranskat)abstract
- Tunnel field-effect transistors (TFETs) are promising candidates that have demonstrated potential for and beyond the 3 nm technology node. One major challenge for the TFETs is to optimize the heterojunction for high drive currents while achieving steep switching. Thus far, such optimization has mainly been addressed theoretically. Here, we experimentally investigate the influence of the source segment composition on the performance for vertical nanowire InAs/InGaAsSb/GaSb TFETs. Compositional analysis using transmission electron microscopy is combined with simulations to interpret the results from electrical characterization data. The results show that subthreshold swing (S) and transconductance (gm) decrease with increasing arsenic composition until the strain due to lattice mismatch increases them both. The role of indium concentration at the junction is also examined. This systematic optimization has rendered sub-40 mV/dec operating TFETs with a record transconductance efficiency gm/ID = 100 V-1, and it shows that different source materials are preferred for various applications.
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| 5. |
- Persson, Anton E. O., et al.
(författare)
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Integration of Ferroelectric HfxZr1-xO2 on Vertical III-V Nanowire Gate-All-Around FETs on Silicon
- 2022
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 43:6, s. 854-857
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a successful process scheme for the integration of a CMOS-compatible ferroelectric gate stack on a scaled vertical InAs nanowire gate-all-around MOSFET on silicon. The devices show promising device characteristics with nanosecond write time and large memory window of >1.5 V. In the current implementation, the device performance is mainly limited by access resistance, which is attributed to the thermal sensitivity of InAs. The findings indicate that the ferroelectricity is not intrinsically preventing future improvements of scaled III-V FeFETs.
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| 6. |
- Rangasamy, Gautham, et al.
(författare)
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gm/Id Analysis of vertical nanowire III–V TFETs
- 2023
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Ingår i: Electronics Letters. - 1350-911X. ; 59:18
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data on analog performance of gate-all-around III-V vertical Tunnel Field-Effect Transistors (TFETs) and circuits are presented. The individual device shows a minimal subthreshold swing of 44 mV/dec and transconductance efficiency of 50 V−1 for current range of 9 nA/μm to 100 nA/μm and at a drain voltage of 100 mV. This TFET demonstrates translinearity between transconductance and drain current for over a decade of current, paving way for low power current-mode analog IC design. To explore this design principle, a current conveyor circuit is implemented, which exhibits large-signal voltage gain of 0.89 mV/mV, current gain of 1nA/nA and an operating frequency of 320 kHz. Furthermore, at higher drain bias of 500 mV, the device shows maximum transconductance of 72 μS/μm and maximum drain current of 26 μA/μm. The device, thereby, can be operated as a current mode device at lower bias voltage and as voltage mode device at higher bias voltage.
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| 7. |
- Rangasamy, Gautham, et al.
(författare)
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High Current Density Vertical Nanowire TFETs With I₆₀ > 1 μ A/ μ m
- 2023
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Ingår i: IEEE Access. - 2169-3536. ; 11, s. 95692-95696
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental data for a vertical, 22-nm-diameter InAs/(In)GaAsSb nanowire Tunnel Field-Effect Transistor that exhibits the highest reported I60 of 1.2 μA/μm , paving the way for low power applications. The transistor reaches a minimum subthreshold swing of 43 mV/dec at VDS = 300 mV with a sub-60 mV/dec operation over a wide current range. Combined with a high transconductance of 205 μS/μm , the ON-current for the same device is 18.6 μA/μm at VDS = 300 mV for IOFF of 1 nA/ μm.
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| 8. |
- Rangasamy, Gautham, et al.
(författare)
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Source Design of Vertical III-V Nanowire Tunnel Field-Effect Transistors
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Ingår i: IEEE Journal on Exploratory Solid-State Computational Devices and Circuits. - 2329-9231. ; 10, s. 8-12
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Tidskriftsartikel (refereegranskat)abstract
- We systematically fabricate devices and analyse data for vertical InAs/(In)GaAsSb nanowire Tunnel Field-Effect Transistors, to study the influence of source dopant position and level on their device performance. The results show that delaying the introduction of dopants further in the GaAsSb source segments improved the transistor metrics (subthreshold swing and the ON-current performance), due to the formation of a nid-InAsSb segment. The devices display a minimum subthreshold swing of 26 mV/dec and ON-current of 10.2 μA/μm at V DS of 300 mV. The performance of devices were improved further by optimizing the doping levels which led to record subthermal current of 1.2 μA/μm and transconductance of 205 μS/μm at V DS of 500 mV.
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| 9. |
- Rangasamy, Gautham, et al.
(författare)
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TFET Circuit Configurations Operating below 60 mV/dec
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Ingår i: IEEE Transactions on Nanotechnology. - 1536-125X. ; , s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Tunnel Field-Effect Transistors (TFETs) offer more energy efficient alternative to CMOS for design of low power circuits. In spite of this potential, circuits based on TFETs have not been experimentally demonstrated so far. In this letter, we explore TFET fabrication and basic functionality of n-TFET based circuits in the following configurations: a current mirror, a diode-connected inverter, and a cascode. Individual TFETs in the circuit operate well below 60 mV/dec operation with minimum achieved subthreshold swing (SS) of 30 mV/dec at drain voltage of 400 mV. To analyse the circuit operation, individual devices are connected via FEOL and are biased at 300 mV supply voltage, with an input frequency of 200 kHz. The measured circuit configurations demonstrate the expected functionality.
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| 10. |
- Zhu, Zhongyunshen, et al.
(författare)
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Compressively-strained GaSb nanowires with core-shell heterostructures
- 2020
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 13:9, s. 2517-2524
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Tidskriftsartikel (refereegranskat)abstract
- GaSb-based nanowires in a gate-all-around geometry are good candidates for binary p-type transistors, however they require the introduction of compressive strain to enhance the transport properties. Here, we for the first time demonstrate epitaxial GaSb-GaAsxSb1−x core-shell nanowires with a compressively strained core. Both axial and hydrostatic strain in GaSb core have been measured by X-ray diffraction (XRD) and Raman scattering, respectively. The optimal sample, almost without plastic relaxation, has an axial strain of −0.88% and a hydrostatic strain of −1.46%, leading to a noticeable effect where the light hole band is calculated to be 33.4 meV above the heavy hole band at the Γ-point. This valence band feature offers more light holes to contribute the transport process, and thus may provide enhanced hole mobility by reducing both the interband scattering and the hole effective mass. Our results show that lattice-mismatched epitaxial core-shell heterostructures of high quality can also be realized in the promising yet demanding GaSb-based system. [Figure not available: see fulltext.].
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