Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Materials (Basel) ; 12(16)2019 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395796

RESUMO

We present a low-noise photodetector based on van der Waals stacked black phosphorus (BP)/boron nitride (h-BN)/graphene tunneling junctions. h-BN acts as a tunneling barrier that significantly blocks dark current fluctuations induced by shallow trap centers in BP. The device provides a high photodetection performance at mid-infrared (mid-IR) wavelengths. While it was found that the photoresponsivity is similar to that in a BP photo-transistor, the noise equivalent power and thus the specific detectivity are nearly two orders of magnitude better. These exemplify an attractive platform for practical applications of long wavelength photodetection, as well as provide a new strategy for controlling flicker noise.

2.
Nanoscale Res Lett ; 14(1): 202, 2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31187310

RESUMO

This paper investigates the impacts of post metal annealing (PMA) and post deposition annealing (PDA) on the electrical performance of Ge p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) with ZrO2 dielectric. For the transistors without PDA, on-state current (ION), subthreshold swing (SS), and capacitance equivalent thickness (CET) characteristics are improved with PMA temperature increasing from 350 to 500 °C. Crystallization of ZrO2 dielectric at the higher PMA temperature contributes to the increase of the permittivity of ZrO2 and the decrease of the density of interface states (Dit), resulting in a reduced CET and high effective hole mobility (µeff). It is demonstrated that Ge pMOSFETs with a PDA treatment at 400 °C have a lower CET and a steeper SS but a lower µeff compared to devices without PDA.

3.
Appl Opt ; 58(16): 4400-4405, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31251249

RESUMO

In this study, we investigate the whispering gallery modes (WGMs) of a 14-layer black phosphorous (BP) phototransistor based on a silicon microdisk. The transmission characteristics of the waveguide-coupled microdisk resonator with and without BP are analyzed to determine the resonance wavelength. The effect of BP on the electric field distributions of the WGMs of the Si microdisk resonator is simulated by using the finite-element method. In addition, the enhanced optical absorption of the BP-covered Si microdisk resonator is further analyzed by the coupled mode theory. Contrastingly, the device also functions as a phototransistor with a peak responsivity of 328.1 A/W and high field-effect mobility of nearly 466.6 cm2 V-1 s-1. Our proposed device paves the path for the exploitation of BP optoelectronics devices with the assistance of optical microresonators in the near-infrared range (NIR).

4.
Nanoscale Res Lett ; 14(1): 171, 2019 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-31127388

RESUMO

We demonstrate the negative capacitance (NC) effect of HfZrOx-based field-effect transistors (FETs) in the experiments. Improved IDS, SS, and Gm of NCFET have been achieved in comparison with control metal oxide semiconductor (MOS) FET. In this experiment, the bottom MIS transistors with different passivation time are equivalent to the NC devices with different MOS capacitances. Meanwhile, the electrical properties of NCFET with 40 min passivation are superior to that of NCFET with 60 min passivation owing to the good matching between CFE and CMOS. Although SS of sub-60 mV/decade is not achieved, the non-hysteretic transfer characteristics beneficial to the logic applications are obtained.

5.
Nanoscale Res Lett ; 14(1): 125, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30949867

RESUMO

Germanium (Ge) negative capacitance field-effect transistors (NCFETs) with various Zr compositions in Hf1-xZrxO2 (x = 0.33, 0.48, and 0.67) are fabricated and characterized. For each Zr composition, the NCFET exhibits the sudden drop in some points of subthreshold swing (SS), which is induced by the NC effect. Drive current IDS increases with the increase of annealing temperature, which should be due to the reduced source/drain resistance and improved carrier mobility. The steep SS points are repeatable and stable through multiple DC sweeping measurement proving that they are induced by the NC effect. The values of gate voltage VGS corresponding to steep SS are consistent and clockwise IDS-VGS are maintained through the multiple DC sweeps. At fixed annealing temperature, NC device with Hf0.52Zr0.48O2 achieves the higher IDS but larger hysteresis compared to the other compositions. NCFET with Hf0.67Zr0.33O2 can obtain the excellent performance with hysteresis-free curves and high IDS.

6.
Nanoscale Res Lett ; 14(1): 115, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30937641

RESUMO

We report a novel nanocrystal-embedded-insulator (NEI) ferroelectric field-effect transistor (FeFET) with very thin unified-ferroelectric/dielectric (FE/DE) insulating layer, which is promising for low-voltage logic and non-volatile memory (NVM) applications. The ferroelectric nature of the NEI layers comprising orthorhombic ZrO2 nanocrystals embedded in amorphous Al2O3 is proved by polarization voltage measurements, piezoresponse force microscopy, and electrical measurements. The temperature dependent performance and endurance behavior of a NEI negative capacitance FET (NCFET) are investigated. A FeFET with 3.6 nm thick FE/DE achieves a memory window larger than 1 V, paving a pathway for ultimate scaling of FE thickness to enable three-dimensional FeFETs with very small fin pitch.

7.
Nanoscale Res Lett ; 14(1): 126, 2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30953229

RESUMO

A comparison study on electrical performance of Ge pMOSFETs with a GeOx passivation layer formed by ozone post oxidation (OPO) and plasma post oxidation (PPO) is performed. PPO and OPO were carried out on an Al2O3/n-Ge (001) substrate followed by a 5-nm HfO2 gate dielectric in situ deposited in an ALD chamber. The quality of the dielectric/Ge interface layer was characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The PPO treatment leads to a positive threshold voltage (VTH) shift and a lower ION/IOFF ratio, implying a poor interface quality. Ge pMOSFETs with OPO exhibit a higher ION/IOFF ratio (up to four orders of magnitude), improved subthreshold swing, and enhanced carrier mobility characteristics as compared with PPO devices. A thicker Al2O3 block layer in the OPO process leads to a higher mobility in Ge transistors. By comparing two different oxidation methods, the results show that the OPO is an effective way to increase the interface layer quality which is contributing to the improved effective mobility of Ge pMOSFETs.

8.
Nanoscale Res Lett ; 14(1): 15, 2019 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-30623254

RESUMO

We report the amorphous Si passivation of Ge pMOSFETs fabricated on (001)-, (011)-, and (111)-orientated surfaces for advanced CMOS and thin film transistor applications. Amorphous Si passivation of Ge is carried out by magnetron sputtering at room temperature. With the fixed thickness of Si tSi, (001)-oriented Ge pMOSFETs achieve the higher on-state current ION and effective hole mobility µeff compared to the devices on other orientations. At an inversion charge density Qinv of 3.5 × 1012 cm-2, Ge(001) transistors with 0.9 nm tSi demonstrate a peak µeff of 278 cm2/V × s, which is 2.97 times higher than the Si universal mobility. With the decreasing of tSi, ION of Ge transistors increases due to the reduction of capacitive effective thickness, but subthreshold swing and leakage floor characteristics are degraded attributed to the increasing of midgap Dit.

9.
Opt Express ; 26(21): 27683-27693, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-30469830

RESUMO

In this work, a periodic bowtie structure based on black phosphorus (BP) is theoretically proposed and characterized. It is demonstrated that localized surface plasmons can be excited in the BP nanoantennas at terahertz (THz) frequencies. Numerical investigations, using the numerical method finite-difference time-domain (FDTD), have been utilized to analyze the the dimensions' impact on absorption spectra. Furthermore, the electric field distribution is plotted and discussed to explain the resonance wavelength tuning by different geometrical sizes of the structure. Results reveal that the optimized BP bow-tie structure can be allowed for the realization of two-dimensional nanophotonics at terahertz frequencies.

10.
Nanoscale Res Lett ; 13(1): 237, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30112730

RESUMO

We investigate the metal-insulator-semiconductor contacts on n-Ge utilizing a ZnO interfacial layer (IL) to overcome the Fermi-level pinning (FLP) effect at metal/Ge interface and reduce the barrier height for electrons. A small conduction band offset of 0.22 eV at the interface between ZnO and n-Ge is obtained, and the ZnO IL leads to the significant reduced contact resistance (Rc) in metal/ZnO/n-Ge compared to the control device without ZnO, due to the elimination of FLP. It is observed that the argon (Ar) plasma treatment of ZnO can further improve the Rc characteristics in Al/ZnO/n-Ge device, which is due to that Ar plasma treatment increases the concentration of oxygen vacancy Vo, acting as n-type dopants in ZnO. The ohmic contact is demonstrated in the Al/ZnO/n-Ge with a dopant concentration of 3 × 1016 cm-3 in Ge. On the heavily doped n+-Ge with a phosphor ion (P+) implantation, a specific contact resistivity of 2.86 × 10- 5 Ω cm2 is achieved in Al/ZnO/n+-Ge with Ar plasma treatment.

11.
Opt Express ; 25(20): 24705-24713, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-29041416

RESUMO

In this paper, we design the uniaxially and biaxially strained black phosphorus (BP) photodetectors. Different strains applied in the zigzag or armchair direction can effectively tune the direct band gap of 5-layer of BP. The optical field intensity is modeled to determine the absorption for the BP layer. The strain effect on the band structure of BP is investigated using first-principles method based on density functional theory. The cut-off wavelength of strained 5-layer of BP pin photodetector is extended to middle infrared range with a high responsivity of 66.29 A/W, which means that the strained black phosphorus photodetector provides a new approach for the middle-infrared range optoelectronic devices.

12.
Nanoscale Res Lett ; 12(1): 120, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28228005

RESUMO

Well-behaved Ge quantum well (QW) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) were fabricated on silicon-on-insulator (SOI) substrate. By optimizing the growth conditions, ultrathin fully strained Ge film was directly epitaxially grown on SOI at about 450 °C using ultra-high vacuum chemical vapor deposition. In situ Si2H6 passivation of Ge was utilized to form a high-quality SiO2/Si interfacial layer between the high-κ dielectric and channels. Strained Ge QW pMOSFETs achieve the significantly improved effective hole mobility µ eff as compared with the relaxed Si and Ge control devices. At an inversion charge density of Q inv of 2 × 1012 cm-2, Ge QW pMOSFETs on SOI exhibit a 104% µ eff enhancement over relaxed Ge control transistors. It is also demonstrated that µ eff of Ge pMOSFETs on SOI can be further boosted by applying an external uniaxial compressive strain.

13.
Opt Express ; 25(2): 1278-1287, 2017 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-28158011

RESUMO

In this paper, we propose an ultrathin THz plasmonic metallic strip based on graded grating structure with thermo-optic material, which exhibits a strong engineering of trapping and releasing electromagnetic waves in terahertz regimes. The dispersion properties of the ultrathin spoof slow-wave plasmonic graded grating waveguide are characterized using the finite element method, and the propagation characteristics of the grating structures are thoroughly analyzed by the dispersion curves, electric field magnitude distribution, and electric field vertical distribution. The gradient grating waveguide is demonstrated to be an ideal slow-wave system for trapping and releasing surface plasmon polaritons (SPPs) waves through tuning the refractive index of the thermo-optic material. The reflected location for the SPPs waves on the graded corrugated metal strip at 1.1 THz at different temperatures are compared. It is proved that such ultrathin gradient grating waveguide provides an excellent performance for trapping and releasing surface waves at THz, which permits applications for future optical communications.

14.
Appl Opt ; 55(34): 9668-9674, 2016 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-27958455

RESUMO

We comprehensively investigate the energy band diagrams, carrier distribution, spontaneous emission rate rsp, and the internal quantum efficiency ηIQE in the lattice-matched GeSn/SiGeSn double heterostructure light-emitting diode (LED) wrapped in a Si3N4 liner stressor. The large tensile strain introduced into the device by the expansion of the Si3N4 liner is characterized by numerical simulation. A lower Sn composition required for the indirect to direct bandgap transition and a higher ratio of the electron occupation probability in the Γ conduction valley are achieved in the tensile strained GeSn/SiGeSn LED in comparison with the relaxed device. Analytical calculation shows that the tensile strained LED wrapped in the Si3N4 liner stressor exhibits the improved rsp and ηIQE compared to the relaxed device. rsp and ηIQE also can be enhanced by increasing Sn composition, carrier injection density, and n-type doping concentration in the GeSn active layer.

15.
Appl Opt ; 55(7): 1720-4, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26974635

RESUMO

We investigate the dispersion properties of an ultrathin spoof plasmonic waveguide based on metal strip grooves using the finite element method. The confinement ability of the surface plasmon polariton (SPP) waves are influenced by the dispersion curves, which can be modulated by the structure parameters. The propagation characteristics of a subwavelength planar plasmonic waveguide ring resonator have also been studied. Furthermore, a gain medium is introduced to compensate for the propagation loss of the SPP wave in the device at terahertz frequency. It is demonstrated that the gain medium provides an enhancement for the control of on/off states of the signal with the presence of pumping, which paves a way for gain-assisted switching and lasing applications in the terahertz regime.

16.
Opt Express ; 23(2): 739-46, 2015 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-25835833

RESUMO

In this paper, we design a biaxial tensile strained GeSn photodetector with fin structure wrapped in Si(3)N(4) liner stressor. A large biaxial tensile strain is induced in GeSn fins by the expansion of Si(3)N(4) liner stressor. The distribution of tensile strain in GeSn fins was calculated by a finite element simulation. It is observed that magnitude of the strain increases with the reduction of fin thickness T(fin). Under the biaxial tensile strain, the direct band gap E(G,Γ) of GeSn fin photodetector is significantly reduced by lowering Γ conduction valley in energy and lifting of degeneracy of valence bands. As the 30 nm Si(3)N(4) liner stressor expanses by 1%, a E(G,Γ) reduction of ~0.14 eV is achieved in Ge(0.92)Sn(0.08) fins with a T(fin) of 100 nm. The cut-off wavelengths of strained Ge(0.96)Sn(0.04), Ge(0.92)Sn(0.08) and Ge(0.90)Sn(0.10) fin photodetectors with a T(fin) of 100 nm are extended to 2.4, 3.3, and 4 µm, respectively. GeSn fin photodetector integrated with Si(3)N(4) liner stressor provides an effective technique for extending the absorption edge of GeSn with Sn composition less than 10% to mid-infrared wavelength.

17.
Opt Express ; 23(6): 7924-32, 2015 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-25837129

RESUMO

We theoretically investigate a tensile strained GeSn waveguide integrated with Si3N4 liner stressor for the applications in mid-infrared (MIR) detector and modulator. A substantial tensile strain is induced in a 1 × 1 µm² GeSn waveguide by the expansion of 500 nm Si3N4 liner stressor and the contour plots of strain are simulated by the finite element simulation. Under the tensile strain, the direct bandgap E(G,Γ) of GeSn is significantly reduced by lowering the Γ conduction valley in energy and lifting of degeneracy of valence bands. Absorption coefficients of tensile strained GeSn waveguides with different Sn compositions are calculated. As the Si3N4 liner stressor expands by 1%, the cut-off wavelengths of tensile strained Ge(0.97)Sn(0.03), Ge(0.95)Sn(0.05), and Ge(0.90)Sn(0.10) waveguide photodetectors are extended to 2.32, 2.69, and 4.06 µm, respectively. Tensile strained Ge(0.90)Sn(0.10) waveguide electro-absorption modulator based on Franz-Keldysh (FK) effect is demonstrated in theory. External electric field dependence of cut-off wavelength and propagation loss of tensile strained Ge(0.90)Sn(0.10) waveguide is observed, due to the FK effect.

18.
Appl Opt ; 53(27): 6302-6, 2014 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-25322111

RESUMO

In this paper, we propose a new dual slot based on rib-like structure, which exhibits a flat and near-zero dispersion over a 198 nm wide wavelength range. Chromatic dispersion of dual-slot silicon (Si) waveguide is mainly determined by waveguide dispersion due to the manipulating mode effective area rather than by the material dispersion. Moreover, the nonlinear coefficient and effective mode area of the waveguide are also explored in detail. A nonlinear coefficient of 1460/m/W at 1550 nm is achieved, which is 10 times larger than that of the Si rib waveguide. By changing different waveguide variables, both the dispersion and nonlinear coefficient can be tailored, thus enabling the potential for a highly nonlinear waveguide with uniform dispersion over a wide wavelength range, which could benefit the performance of broadband optical signal systems.

19.
Nanoscale ; 6(20): 11803-9, 2014 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-25163912

RESUMO

Ag-In-Zn-S nanorods with tunable photoluminescence were formed by a convenient synthetic approach, and the nanorods demonstrated a relatively long fluorescence lifetime of 1.248 µs. In addition, Ag-In-Zn-S nanorods of nail shape and rod-particle dimers were successfully produced by adjusting the reaction parameters.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA