Showing papers on "Schottky barrier published in 2008"
TL;DR: This NC device produces one of the largest short-circuit currents of any nanostructured solar cell, without the need for sintering, superlattice order or separate phases for electron and hole transport.
Abstract: We describe here a simple, all-inorganic metal/NC/metal sandwich photovoltaic (PV) cell that produces an exceptionally large short-circuit photocurrent (>21 mA cm -2 ) by way of a Schottky junction at the negative electrode. The PV cell consists of a PbSe NC film, deposited via layer-by-layer (LbL) dip coating that yields an EQE of 55-65% in the visible and up to 25% in the infrared region of the solar spectrum, with a spectrally corrected AM1.5G power conversion efficiency of 2.1%. This NC device produces one of the largest short-circuit currents of any nanostructured solar cell, without the need for sintering, superlattice order or separate phases for electron and hole transport.
941 citations
TL;DR: The photocurrent of the device is associated with a light-induced desorption of oxygen from the nanoparticle surfaces, thus removing electron traps and increasing the free carrier density which in turn reduces the Schottky barrier between contacts and ZnO nanoparticles for electron injection.
Abstract: A “visible-blind” solution-processed UV photodetector is realized on the basis of colloidal ZnO nanoparticles. The devices exhibit low dark currents with a resistance >1 TΩ and high UV photocurrent efficiencies with a responsivity of 61 A/W at an average intensity of 1.06 mW/cm2 illumination at 370 nm. The characteristic times for the rise and fall of the photocurrent are <0.1 s and about 1 s, respectively. The photocurrent of the device is associated with a light-induced desorption of oxygen from the nanoparticle surfaces, thus removing electron traps and increasing the free carrier density which in turn reduces the Schottky barrier between contacts and ZnO nanoparticles for electron injection. The devices are promising for use in large-area UV photodetector applications.
735 citations
TL;DR: The strain sensor developed here has applications in strain and stress measurements in cell biology, biomedical sciences, MEMS devices, structure monitoring, and more.
Abstract: Strain sensors based on individual ZnO piezoelectric fine-wires (PFWs; nanowires, microwires) have been fabricated by a simple, reliable, and cost-effective technique. The electromechanical sensor device consists of a single electrically connected PFW that is placed on the outer surface of a flexible polystyrene (PS) substrate and bonded at its two ends. The entire device is fully packaged by a polydimethylsiloxane (PDMS) thin layer. The PFW has Schottky contacts at its two ends but with distinctly different barrier heights. The I-V characteristic is highly sensitive to strain mainly due to the change in Schottky barrier height (SBH), which scales linear with strain. The change in SBH is suggested owing to the strain induced band structure change and piezoelectric effect. The experimental data can be well-described by the thermionic emission-diffusion model. A gauge factor of as high as 1250 has been demonstrated, which is 25% higher than the best gauge factor demonstrated for carbon nanotubes. The strain sensor developed here has applications in strain and stress measurements in cell biology, biomedical sciences, MEMS devices, structure monitoring, and more.
730 citations
TL;DR: In this article, the diffusion and recombination in an absorber blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) with indium tin oxide (ITO) and aluminium contacts have been analyzed in the dark by means of impedance spectroscopy.
547 citations
TL;DR: In this paper, the authors studied both the electron and hole conduction of nanotube transistors and found that the sensing mechanisms can be unambiguously identified from extensive protein-adsorption experiments on such devices.
Abstract: Carbon nanotube transistors have outstanding potential for electronic detection of biomolecules in solution The physical mechanism underlying sensing however remains controversial, which hampers full exploitation of these promising nanosensors Previously suggested mechanisms are electrostatic gating, changes in gate coupling, carrier mobility changes, and Schottky barrier effects We argue that each mechanism has its characteristic effect on the liquid gate potential dependence of the device conductance By studying both the electron and hole conduction, the sensing mechanisms can be unambiguously identified From extensive protein-adsorption experiments on such devices, we find that electrostatic gating and Schottky barrier effects are the two relevant mechanisms, with electrostatic gating being most reproducible If the contact region is passivated, sensing is shown to be dominated by electrostatic gating, which demonstrates that the sensitive part of a nanotube transistor is not limited to the contact region, as previously suggested Such a layout provides a reliable platform for biosensing with nanotubes
455 citations
TL;DR: In situ local oxidation of patterned epitaxial graphene has been achieved, and a lower limit of the GO mobility was found to be 850 cm2/V s, rivaling silicon.
Abstract: Graphene-oxide (GO) flakes have been deposited to bridge the gap between two epitaxial-graphene electrodes to produce all-graphene devices. Electrical measurements indicate the presence of Schottky barriers at the graphene/graphene-oxide junctions, as a consequence of the band gap in GO. The barrier height is found to be about 0.7 eV, and is reduced after annealing at 180 degrees C, implying that the gap can be tuned by changing the degree of oxidation. A lower limit of the GO mobility was found to be 850 cm2/V s, rivaling silicon. In situ local oxidation of patterned epitaxial graphene has been achieved.
331 citations
TL;DR: A novel approach for fabricating diodes and switches that rely on a strain governed piezoelectric-semiconductor coupling process and a new piezotronic switch device with an "on" and "off" ratio of approximately 120 has been demonstrated.
Abstract: Using a two-end bonded ZnO piezoelectric-fine-wire (PFW) (nanowire, microwire) on a flexible polymer substrate, the strain-induced change in I−V transport characteristic from symmetric to diode-type has been observed. This phenomenon is attributed to the asymmetric change in Schottky-barrier heights at both source and drain electrodes as caused by the strain-induced piezoelectric potential-drop along the PFW, which have been quantified using the thermionic emission−diffusion theory. A new piezotronic switch device with an “on” and “off” ratio of ∼120 has been demonstrated. This work demonstrates a novel approach for fabricating diodes and switches that rely on a strain governed piezoelectric-semiconductor coupling process.
268 citations
TL;DR: In this paper, a gradual change of Schottky barrier heights with increasing insulating film thickness has been found, which supports that the origin of Fermi level pinning at the metal/germanium junction is caused by the metal-induced gap states.
Abstract: At any metal/germanium (Ge) interfaces, Schottky junctions to n-Ge and ohmic ones to p-Ge are formed by the strong Fermi level pinning to the valence band edge of Ge. In this paper, we report that Schottky-ohmic characteristics are reversed by inserting an ultra-thin oxide film into the metal/Ge interface. A gradual change of Schottky barrier heights (SBHs) with increasing insulating film thickness has been found, which supports that the origin of Fermi level pinning at the metal/Ge junction is caused by the metal-induced gap states. Furthermore, the SBH change enables us to operate metal source/drain Ge n-channel metal–oxide–semiconductor field effect transistors (n-MOSFETs) without any impurity doping. We demonstrate the metal source/drain Ge n-MOSFET with a peak mobility of 270 cm2/(Vs).
201 citations
TL;DR: In this paper, a high electron mobility transistor (HEMT)-compatible power lateral field effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN∕GaN HEMT, providing a low-cost solution for GaN power integrated circuits.
Abstract: A high electron mobility transistor (HEMT)-compatible power lateral field-effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN∕GaN HEMT, providing a low-cost solution for GaN power integrated circuits. The power rectifier features a Schottky-gate-controlled two-dimensional electron gas channel between the cathode and anode. By tying up the Schottky gate and anode together, the forward turn-on voltage of the rectifier is determined by the threshold voltage of the channel instead of the Schottky barrier. The L-FER with a drift length of 10μm features a forward turn-on voltage of 0.63V at a current density of 100A∕cm2. This device also exhibits a reverse breakdown voltage (BV) of 390V at a current level of 1mA∕mm and a specific on resistance (RON,sp) of 1.4mΩcm2, yielding a figure of merit (BV2∕RON,sp) of 108MW∕cm2. The excellent device performance, coupled with the lateral device structure and process compatibility with AlGaN∕GaN...
179 citations
TL;DR: In this article, the Schottky barrier height (SBH) of the contact systems of NiSi and PtSi was compared with two different schemes used to incorporate a high concentration of dopants at the silicide/silicon interface.
Abstract: An experimental study is presented to compare two different schemes used to incorporate a high concentration of dopants at the silicide/silicon interface for NiSi and PtSi, i.e., dopant segregation, with the purpose of lowering the Schottky barrier height (SBH) of the contact systems. Specifically, the interfacial dopant is introduced either through silicidation-induced dopant segregation (SIDS) or by silicide as diffusion source (SADS). For the latter, a postimplantation drive-in anneal is needed. For both silicide systems, the dopant segregation gives rise to a predominant effect, leading to an effective SBH that is independent of the original SBHs of PtSi and NiSi, which differs by 0.2 eV. Scheme SIDS is relatively simple in processing, but the silicidation process is dopant-dependent, leading to local variations of silicide formation. Scheme SADS addresses the adverse effect of dopant on silicidation by separating silicidation from dopant incorporation.
167 citations
TL;DR: In this article, a thin Ge3N4 layer is introduced to reduce Fermi level pinning and allow the formation of Ohmic contacts on moderately, n-type doped Ge layers.
Abstract: Severe Fermi level pinning at the interface between n-Ge and a metal leads to the formation of a Schottky barrier, almost independent on the metal work function. Therefore, it seems impossible to form metal Ohmic contacts on moderately, n-type doped Ge layers. For p-type Ge, the Fermi level pinning works opposite: all metal contacts show Ohmic behavior. This fixed behavior can be altered by the introduction of a thin Ge3N4 layer. Ge3N4 seems effective in reducing Fermi level pinning and, therefore, allows the formation of Ohmic contacts on n-type Ge and a rectifying contact on p-type Ge.
Rohm1
TL;DR: In this paper, the Schottky ultraviolet photodiode was constructed with a ZnO (0001) bulk single crystal and a transparent conducting polymer, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), fabricated with a simple spin-coating process at room temperature in air.
Abstract: We report on a high performance visible-blind Schottky ultraviolet photodiode composed of a ZnO (0001) bulk single crystal and a transparent conducting polymer, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), fabricated with a simple spin-coating process at room temperature in air. The quantum efficiency as high as unity in ultraviolet region and a visible rejection ratio of about 103 were achieved in the spectral response of the photodiode under zero-bias condition. The normalized detectivity of the photodiode was evaluated to be 3.6×1014 cm Hz1/2/W at 370 nm.
TL;DR: In this paper, a thin layer of aluminum oxide (Al2O3), formed by oxidation of aluminum (Al), was inserted between the metal/Ge interface to alleviate the strong Fermi-level pinning effect.
Abstract: Due to the strong Fermi-level pinning close to the germanium (Ge) valence band edge, all metal/p-type Ge contacts show Ohmic characteristics, while metal/n-type Ge contacts exhibit rectifying behaviors. In this paper, we report a simple method to alleviate this Fermi-level pinning effect by inserting a thin layer of aluminum oxide (Al2O3), formed by oxidation of aluminum (Al), between the metal/Ge interface. The effective Schottky barrier heights of nickel (Ni)∕n-type Ge, cobalt (Co)∕n-type Ge, and iron (Fe)∕n-type Ge decrease from 0.54, 0.62, and 0.61eV to 0.39, 0.23, and 0.18eV, respectively, with this thin layer of Al2O3. The tunneling oxide significantly suppresses the Fermi-level pinning, and yet does not restrict the current density. This method seems promising to realize low resistance metal contact to n-type Ge, which is essential to realize n-channel Ge complementary metal-oxide-semiconductor field-effect transistor with metal source and drain.
TL;DR: This study provides solid evidence to further prove the mechanism proposed for the piezoelectric NG and piezotronics and tuning its carrier density and the characteristics of the Schottky barrier at the interface between the metal electrode and the NW.
Abstract: By assembling a ZnO nanowire (NW) array based nanogenerator (NG) that is transparent to UV light, we have investigated the performance of the NG by tuning its carrier density and the characteristics of the Schottky barrier at the interface between the metal electrode and the NW. The formation of a Schottky diode at the interface is a must for the effective operation of the NG. UV light not only increases the carrier density in ZnO but also reduces the barrier height. A reduced barrier height greatly weakens the function of the barrier for preserving the piezoelectric potential in the NW for an extended period of time, resulting in little output current. An increased carrier density speeds up the rate at which the piezoelectric charges are screened/neutralized, but a very low carrier density prevents the flow of current through the NWs. Therefore, there is an optimum conductance of the NW for maximizing the output of the NG. Our study provides solid evidence to further prove the mechanism proposed for the ...
TL;DR: In this paper, a vertically well-aligned TiO2−Pt coaxial nanotube array was successfully fabricated by direct current (DC) electrodeposition using anodic aluminum oxide (AAO) templates and the subsequent atmospheric pressure chemical vapor deposition (APCVD) technique.
Abstract: Well-aligned TiO2−Pt coaxial nanotube array schottky structures on Ti substrate (TiO2−Pt/Ti) were successfully fabricated by direct current (DC) electrodeposition using anodic aluminum oxide (AAO) templates and the subsequent atmospheric pressure chemical vapor deposition (APCVD) technique. Environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive X-ray spectra (EDX), and X-ray diffraction patterns (XRD) indicated that the as-prepared samples were a vertically well-aligned TiO2−Pt coaxial nanotube array, and the outer TiO2 nanotube was anatase with the preferential orientation of (101) plane. The asymmetry of the current−voltage (I–V) curve revealed that a schottky barrier had been formed between TiO2 and Pt. The enhanced separation of photogenerated holes and electrons was demonstrated by surface photovoltage (SPV) and photocurrent measurement. For the degradation of phenol under UV light irradiation, the TiO2−Pt coaxial nano...
01 Jan 2008
TL;DR: In this article, a carbon nanotube field effect transistor was designed for field-enhanced spectroscopy using contact barrier engineering (CBE) and Schottky barrier formation at a carbon-to-metal junction.
Abstract: -Study of Nanowire growth mechanisms: VLS & Si-assisted. -One-dimensional SiC nanostructures: Synthesis and its Properties. -Self-organized Nanowire Formation of Si-based Materials. -Optical anisotropy of semiconductor nanowires. -FDTD spectroscopic study of metallic nanostructures: on the pertinent employment of tabulated permittivities. -Electromagnetic nanowire resonances for field-enhanced spectroscopy. -Designing the Carbon Nanotube Field Effect Transistor through Contact Barrier Engineering. -Low dimensional nano-materials for spintronics . -One dimensional phase-change nanomaterials for information storage application. -Ordering of self-assembled quantum wires on InP (001) surfaces. -Schottky barrier formation at a carbon nanotube-metal junction. -X-ray excited optical luminescence characterization of nanowires: sites, surfaces, and symmetries. -Single and multi wall carbon nanotubes: Differences and analogies in their electronic properties. -Controlled formation of nanowire array.
01 Dec 2008
TL;DR: In this article, a dopant segregated Schottky barrier (DSSB) FinFET SONOS device is demonstrated in terms of multi functioning in a high speed NAND-type flash memory and capacitorless 1T-DRAM.
Abstract: A novel dopant segregated Schottky barrier (DSSB) FinFET SONOS device is demonstrated in terms of multi functioning in a high speed NAND-type flash memory and capacitorless 1T-DRAM. In addition, a novel program mechanism that uses energy band engineered hot electrons (EBEHE) energized by sharp energy band bending at the edge of source/drain (S/D) is proposed for a high speed flash memory programming operation. A short program time of 100 ns and a low program voltage of 12 V yield a Vth shift of 3.5 V and a retention time exceeding 10 years. For multi functioning, the operation of a capacitorless 1T-DRAM is also demonstrated with a partially silicided DSSB in the same device.
TL;DR: In this article, the photovoltaic behavior of Schottky barrier devices consisting of a single diindenoperylene (DIP) layer sandwiched between an indium tin oxide and Ag electrode has been investigated.
Abstract: The photovoltaic behavior of Schottky barrier devices consisting of a single diindenoperylene (DIP) layer sandwiched between an indium tin oxide and Ag electrode has been investigated. Correlating the spectral dependence of the photocurrent and the absorption coefficient, we estimated the exciton diffusion length in DIP to ∼100nm along the c′ direction. X-ray structural analysis yielded this length to be in agreement with the average crystallite size, thereby, revealing domain boundaries to be the limiting effect on the exciton transport. The corresponding exciton diffusion constant of 5×10−3cm2∕s resembles that of highly ordered single crystals of polyaromatic hydrocarbons.
TL;DR: In this article, SiSi2∕p-Si detectors with tapered geometry demonstrate dark current of ∼3.0nA at room temperature, responsivity of ∼4.6mA∕W at wavelengths ranging from 1520to1620nm and 3dB bandwidth of ∼2.0GHz.
Abstract: Integrated silicon-on-insulator waveguide-based silicide Schottky-barrier photodetectors were fabricated using low-cost standard Si complementary metal-oxide-semiconductor processing technology. The thin epitaxial NiSi2 layer formed by solid-state Ti-interlayer mediated epitaxy on the top of Si-waveguide absorbs light propagating through the waveguide effectively and exhibits excellent rectifying property on both p-Si and n-Si. NiSi2∕p-Si detectors with tapered geometry demonstrate dark current of ∼3.0nA at room temperature, responsivity of ∼4.6mA∕W at wavelengths ranging from 1520to1620nm, and 3dB bandwidth of ∼2.0GHz. The approaches for further improvement in responsivity are addressed.
TL;DR: It is shown that an insulated electrostatic gate can be used to strongly suppress ubiquitous background charge noise in Schottky-gated GaAs/AlGaAs devices using a 2D self-consistent simulation of the conduction band profile.
Abstract: We show that an insulated electrostatic gate can be used to strongly suppress ubiquitous background charge noise in Schottky-gated GaAs=AlGaAs devices. Via a 2D self-consistent simulation of the conduction band profile we show that this observation can be explained by reduced leakage of electrons from the Schottky gates into the semiconductor through the Schottky barrier, consistent with the effect of ‘‘bias cooling.’’ Upon noise reduction, the noise power spectrum generally changes from Lorentzian to 1/f type. By comparing wafers with different Al content, we exclude that DX centers play a dominant role in the charge noise.
TL;DR: In this article, gate insulation and surface passivation using Zr or Hf was applied to 2m gate-length MOS HEMTs to reduce the gate leakage current by four orders of magnitude and a 2.5 increase of the pulsed drain-current.
Abstract: We present the technology and performance of InAlN/AlN/GaN MOS HEMTs with gate insulation and surface passivation using Zr or Hf . About 10-nm-thick high- dielectrics were deposited by MOCVD before the ohmic contact processing. Plasma pretreatment allowed the reduction of the temperature of the ohmic contact annealing at 600degC. The insulation and passivation of 2-m gate-length MOS HEMTs lead to a gate leakage current reduction by four orders of magnitude and a 2.5 increase of the pulsed drain-current if compared with a Schottky barrier (SB) HEMT. A dc characterization shows 110 mS mm transconductance and 0.9 A mm drain--currents that represent improvements in comparison to the similar SB HEMT and that is explained by a mobility-dependent carrier depletion effect.
TL;DR: In this article, the electrical characterization of PANI/p-Si/Al structure has been investigated by using current-voltage (I-V), capacitance voltages (C-V) and capacitance-frequency (Cf) characteristics.
TL;DR: In this paper, the photoelectric behavior of Pt sandwiched Pb(Zr0.20Ti0.80)TiO3 (PZT) films deposited on Pt∕Ti∕SiO2∕ Si substrates by a sol-gel method was investigated by testing the short-circuit photocurrent under different film thicknesses.
Abstract: Photoelectric behavior of Pt sandwiched Pb(Zr0.20Ti0.80)TiO3 (PZT) films deposited on Pt∕Ti∕SiO2∕Si substrates by a sol-gel method was investigated by testing the short-circuit photocurrent under different film thicknesses. By poling the films step by step with increased magnitude and alternated direction of the dc electric field, interesting photoelectric behavior was found when the PZT films were in virgin or poled up/down state. The photocurrent was also strongly dependent on the film thickness. A simple model was proposed to separate the effects of interface Schottky barriers and bulk ferroelectric polarization of the film on the photocurrent of the Pt/PZT/Pt structure.
TL;DR: In this paper, the authors studied the hydrogen sensing and response characteristics of Pt/GaN and Pt/SiO 2 /GaN (MIS) Schottky diodes under different-concentration hydrogen gases.
Abstract: The hydrogen sensing and response characteristics of Pt/GaN (metal–semiconductor, MS) and Pt/SiO 2 /GaN (metal–insulator–semiconductor, MIS) Schottky diodes under different-concentration hydrogen gases are studied over a wide temperature range in an air atmosphere. Experimentally, the studied MS and MIS devices exhibit hydrogen sensing performance, including forward-bias hydrogen response ( S F ) of 609 (MS) and 14,690 (MIS) (in 9970 ppm H 2 /air), reverse-bias hydrogen response ( S R ) of 5630 (MS) and 44,640 (MIS) (in 9970 ppm H 2 /air), Schottky barrier height variation (Δ ϕ b ) of 195.9 (MS) and 231.6 meV (MIS) (in 9970 ppm H 2 /air), respectively. Based on the equilibrium adsorption analysis, the hydrogen adsorption enthalpy (Δ H °) of the studied MS and MIS devices are −10.21 kJ/mol and −19.5 kJ/mol, respectively. The studied MIS device further shows the excellent performance for high temperature detection and improved activity of hydrogen adsorption reaction. Experimentally, the hydrogen detection adsorption time constants ( τ a ) of the studied MS and MIS devices decrease from 25 to 3 s and from 12 to 2 s, respectively, as the temperature increases from 300 to 700 K. In addition, according to the kinetic adsorption analysis, the activation energy ( E a ) of the studied MS and MIS devices are 4.498 kJ/mol and 2.885 kJ/mol, respectively. This implies that the studied MIS device can also perform more rapid hydrogen detection. Therefore, the studied Pt/SiO 2 /GaN (MIS) Schottky diode exhibits a promise for high performance hydrogen sensor applications.
TL;DR: In this paper, the forward and reverse bias dc characteristics, the long-term stability, and the reverse recovery performance of 4H-SiC junction barrier Schottky (JBS) diodes that are capable of blocking in excess of 10 kV with forward conduction of up to 10 A at a forward voltage of less than 3.5 V (at 25degC).
Abstract: The forward and reverse bias dc characteristics, the long-term stability under forward and reverse bias, and the reverse recovery performance of 4H-SiC junction barrier Schottky (JBS) diodes that are capable of blocking in excess of 10 kV with forward conduction of up to 10 A at a forward voltage of less than 3.5 V (at 25degC) are described. The diodes show a positive temperature coefficient of resistance and a stable Schottky barrier height of up to 200degC. The diodes show stable operation under continuous forward current injection at 20 A/cm2 and under continuous reverse bias of 8 kV at 125degC. When switched from a 10-A forward current to a blocking voltage of 3 kV at a current rate-of-fall of 30 A/mus, the reverse recovery time and the reverse recovery charge are nearly constant at 300 ns and 425 nC, respectively, over the entire temperature range of 25degC-175degC.
TL;DR: In this article, the authors apply the Schottky barrier and heterojunction theory to the problem of indium tin oxide (ITO) and zinc oxide (ZO) interfaces.
TL;DR: In this article, a solar-blind MSM-photodetectors based on the AlGaN/GaN heterostructutes grown by MOCVD technology were fabricated and investigated.
Abstract: Solar-blind MSM-photodetectors based on the AlGaN/GaN heterostructutes grown by MOCVD technology were fabricated and investigated. Directly on the MSM-diode we have measured a Schottky barrier height of 1.1 eV for Ni and 1.4 eV for Mo contacts on AlGaN. Effect of different buffer layers on the detector performances has been demonstrated. Detectors exhibit low dark currents and high sensitivity within the range of 250–290 nm. High-speed response of MSM-detectors is analyzed. Effect of optical excitation level on detector performance is discussed. At low excitation level the detector speed of response is limited by parasitic capacitance of interdigitated diode structure and by the transit time of the photogenerated carriers. At high excitation level the detector speed of response is limited by the field screening caused by the space-charge of the holes. The impulse response of AlGaN/GaN MSM-detector is compared favorably with GaAs MSM-device.
TL;DR: The semi-infinite graphene sheet contacts show the worst performance because of their very low density of states around the Dirac point resulting in low transmission possibility through the Schottky barrier, both at ON and OFF states.
Abstract: The effects of the various contact types and shapes on the performance of Schottky barrier graphene nanoribbon field-effect-transistors (GNRFETs) have been investigated using a real-space quantum transport simulator based on the NEGF approach self-consistently coupled to a three-dimensional Poisson solver for treating the electrostatics. The device channel considered is a double gate semiconducting armchair nanoribbon. The types of contacts considered are (a) a semi-infinite normal metal, (b) a semi-infinite graphene sheet, (c) finite size rectangular shape armchair graphene contacts, (d) finite size wedge shape graphene contacts, and (e) zigzag graphene nanoribbon contacts. Among these different contact types, the semi-infinite graphene sheet contacts show the worst performance because of their very low density of states around the Dirac point resulting in low transmission possibility through the Schottky barrier, both at ON and OFF states. Although all other types of contacts can have significant enhanc...
TL;DR: In this article, the Schottky barrier height was 0.87 eV, with an average ideality factor of 1.6, and threshold gate voltages required for complete pinch off were as small as -2.6 V, and transconductances exceeded 1.4 µS.
Abstract: In this paper, we demonstrate novel MESFETs based on individual GaN nanowires. The Pt/Au Schottky gates exhibited excellent two-terminal Schottky diode rectification behavior. The average effective Schottky barrier height was 0.87 eV, with an average ideality factor of 1.6. In addition, the Schottky gates efficiently modulated the conduction of the nanowires. The threshold gate voltages required for complete pinch off were as small as -2.6 V, and transconductances exceeded 1.4 muS. Subthreshold swings approaching 60 mV/decade and on/off current ratios of up to 5times108 were achieved. These results show that the Schottky gate has the potential to significantly improve the performance of GaN nanowire field-effect devices.