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1.
In this paper, we present the effects of ultrathin Si interfacial layer on the physical and electrical properties of GaAs MOS capacitors fabricated using RF-sputtered HfAlOx gate dielectric. It is found that HfAlOx/Si/n-GaAs stack exhibits excellent electrical properties with low frequency dispersion (∼4.8%), hysteresis voltage (0.27 V) and interface trap density (1.3 × 1012 eV−1 cm−2). The current density of 3.7 × 10−5 A/cm2 is achieved with an equivalent-oxide-thickness of 1.8 nm at VFB + 1 V for Si-passivated HfAlOx films on n-GaAs. X-ray photoelectron spectroscopy (XPS) analysis shows that the suppression of low-k interfacial layer formation is accomplished with the introduction of ultrathin Si interface control layer (ICL). Thus the introduction of thin layer of Si between HfAlOx dielectrics and GaAs substrate is an effective way to improve the interface quality such as low frequency dispersion, hysteresis voltage and leakage current. Additionally, current conduction mechanism has been studied and the dominant conduction mechanisms are found to be Schottky emission at low to medium electric fields and Poole-Frenkel at high fields and high temperatures under substrate injection. In case of gate injection, the main current conduction at low field is found to be the Schottky emission at high temperatures. 相似文献
2.
A study on interface states density distribution and characteristic parameters of the In/SiO2/p-Si (MIS) capacitor has been made. The thickness of the SiO2 film obtained from the measurement of the corrected capacitance in the strong accumulation region for MIS Schottky diodes was 220 Å. The diode parameters from the forward bias I-V characteristics such as ideality factor, series resistance and barrier heights were found to be 1.75, 106-112 Ω and 0.592 eV, respectively. The energy distribution of the interface state density Dit was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density obtained using the I-V characteristics had an exponential growth, with bias towards the top of the valance band, from 9.44×1013 eV−1 cm−2 in 0.329-Ev eV to 1.11×1013 eV−1 cm−2 in 0.527-Ev eV at room temperature. Furthermore, the values of interface state density Dit obtained by the Hill-Coleman method from the C-V characteristics range from 52.9×1013 to 1.11×1013 eV−1 cm−2 at a frequency range of 30kHz-1 MHz. These values of Dit and Rs were responsible for the non-ideal behaviour of I-V and C-V characteristics. 相似文献
3.
M. Caymax M. Houssa G. Pourtois F. Bellenger K. Martens A. Delabie S. Van Elshocht 《Applied Surface Science》2008,254(19):6094-6099
Important progress has been made in the passivation of Ge/gate dielectric interfaces. One important approach is by thermally oxidized GeO2 interface and ALD high-k layers, with an interface state density Dit ∼ 2 × 1011 cm−2 eV−1. Another approach is with an epi-Si/SiO2 interface, resulting in similar Dit. Hysteresis and Vth shift, however, are still not optimal. Extensive material characterization and theoretical insights help us understanding the root cause of these remaining issues and show the way to improved interface control. 相似文献
4.
Metal-oxide-semiconductor (MOS) capacitors incorporating hafnium dioxide (HfO2) dielectrics were fabricated and investigated. In this work, the electrical and interfacial properties were characterized based on capacitance-voltage (C-V) and current-voltage (I-V) measurements. Thereafter the current conduction mechanism, electron effective mass (m*), mean density of interface traps per unit area and energy (), energy distribution of interface traps density and near-interface oxide traps density (NNIOT) were studied in details. The characterization reveals that the dominant conduction mechanism in the region of high temperature and high field is Schottky emission. The mean density of interface traps per unit area and energy is about 6.3 × 1012 cm−2 eV−1 by using high-low frequency capacitance method. The maximum Dit is about 7.76 × 1012 cm−2 eV−1 located at 0.27 eV above the valence band. 相似文献
5.
The present status and key issues of surface passivation technology for III-V surfaces are discussed in view of applications to emerging novel III-V nanoelectronics. First, necessities of passivation and currently available surface passivation technologies for GaAs, InGaAs and AlGaAs are reviewed. Then, the principle of the Si interface control layer (ICL)-based passivation scheme by the authors’ group is introduced and its basic characterization is presented. Ths Si ICL is a molecular beam epitaxy (MBE)-grown ultrathin Si layer inserted between III-V semiconductor and passivation dielectric. Finally, applications of the Si ICL method to passivation of GaAs nanowires and GaAs nanowire transistors and to realization of pinning-free high-k dielectric/GaAs MOS gate stacks are presented. 相似文献
6.
P. Darmawan 《Solid State Communications》2006,138(12):571-573
Amorphous Lu2O3 high-k gate dielectrics were grown directly on n-type (100) Si substrates by the pulsed laser deposition (PLD) technique. High-resolution transmission electron microscope (HRTEM) observation illustrated that the Lu2O3 film has amorphous structure and the interface with Si substrate is free from amorphous SiO2. An equivalent oxide thickness (EOT) of 1.1 nm with a leakage current density of 2.6×10−5 A/cm2 at 1 V accumulation bias was obtained for 4.5 nm thick Lu2O3 thin film deposited at room temperature followed by post-deposition anneal (PDA) at 600 °C in oxygen ambient. The effects of PDA process and light illumination were studied by capacitance-voltage (C-V) and current density-voltage (J-V) measurements. It was proposed that the net fixed charge density and leakage current density could be altered significantly depending on the post-annealing conditions and the capability of traps to trap and release charges. 相似文献
7.
Mehmet Ali Ebeo?lu 《Physica B: Condensed Matter》2008,403(1):61-66
Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density Nss with and without taking into account the series resistance Rs. While the interface state density calculated without taking into account Rs has increased exponentially with bias from 2.2×1012 cm−2 eV−1 in (Ec−0.48) eV to 3.85×1012 cm−2 eV−1 in (Ec−0.32) eV of n-GaAs, the Nss obtained taking into account the series resistance has remained constant with a value of 2.2×1012 cm−2 eV−1 in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer. 相似文献
8.
In this work we present the results of comparative XPS and PYS studies of electronic properties of the space charge layer of the L-CVD SnO2 thin films after air exposure and subsequent UHV annealing at 400 °C, with a special emphasis on the interface Fermi level position.From the centre of gravity of binding energy of the main XPS Sn 3d5/2 line the interface Fermi level position EF − Ev in the band gap has been determined. It was in a good correlation with the value estimated from the offset of valence band region of the XPS spectrum, as well as from the photoemission yield spectroscopy (PYS) measurements. Moreover, from the valence band region of the XPS spectrum and PYS spectrum two different types of filled electronic band gap states of the L-CVD SnO2 thin films have been derived, located at 6 and 3 eV with respect to the Fermi level. 相似文献
9.
Five-layered Si/SixGe1−x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline SixGe1−x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in SixGe1−x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si0.82Ge0.18 (10 nm) are 2.55 × 106 /°C, 2.56 × 1012 cm−3, 1.28 × 107 cm−2, and 15.8 cm−2/(V s), respectively. 相似文献
10.
Sandwich-structure Al2O3/HfO2/Al2O3 gate dielectric films were grown on ultra-thin silicon-on-insulator (SOI) substrates by vacuum electron beam evaporation (EB-PVD) method. AFM and TEM observations showed that the films remained amorphous even after post-annealing treatment at 950 °C with smooth surface and clean silicon interface. EDX- and XPS-analysis results revealed no silicate or silicide at the silicon interface. The equivalent oxide thickness was 3 nm and the dielectric constant was around 7.2, as determined by electrical measurements. A fixed charge density of 3 × 1010 cm−2 and a leakage current of 5 × 10−7A/cm2 at 2 V gate bias were achieved for Au/gate stack /Si/SiO2/Si/Au MIS capacitors. Post-annealing treatment was found to effectively reduce trap density, but increase in annealing temperature did not made any significant difference in the electrical performance. 相似文献
11.
Physical and electrical properties of sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y2O3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 1012 eV−1 cm−2). The results show that the deposition of Y2O3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y2O3/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10−6 A cm−2 at a VFB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y2O3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y2O3/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively. 相似文献
12.
B.L. Yu 《Optics Communications》2006,258(2):256-263
The absorption spectrum of D2O vapor from 0.2 to 2.0 THz (6.7-67 cm−1) which is associated with rotational modes was measured at one atmosphere using terahertz time-domain spectroscopy (THz-TDS). The linewidth and collisional dephasing times were measured for 26 pure rotational transitions in the ground vibrational state (0 0 0). The temperature dependence of the linewidth (Δν) behaves as Δν ∼ T−3/4 and the linewidth decrease with increasing temperature is attributed to the 1/r6 force of interaction between colliding D2O molecules. 相似文献
13.
C. Terzioglu 《Physica B: Condensed Matter》2008,403(18):3320-3325
Gold (Au) diffusion in superconducting Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was investigated over the temperature range 500-800 °C by the energy dispersive X-ray fluorescence (EDXRF) technique. It is found that the Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependences of Au diffusion coefficient in grains and over grain boundaries are described by the relations D1=6.7×10−5exp(−1.19 eV/kBT) and D2=9.7×10−4exp(−1.09 eV/kBT), respectively. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19%. For the Au-diffused samples, dc electrical resistivity and transport critical current density measurements indicated the critical transition temperature increased from 100 to 104 K and the critical current density increased from 40 to 125 A cm−2, in comparison with those of undoped samples. From scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements it is observed that Au doping of the sample also improved the surface morphology and increased the ratio of the high-Tc phase to the low-Tc phase. The possible reasons for the observed improvement in microstructure and superconducting properties of the samples due to Au diffusion are also discussed. 相似文献
14.
K. Goksen 《Journal of Physics and Chemistry of Solids》2008,69(10):2385-2389
Transmission and reflection measurements in the wavelength region 450-1100 nm were carried out on Tl4In3GaS8-layered single crystals. The analysis of the room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 2.32 and 2.52 eV, respectively. The rate of change of the indirect band gap with temperature dEgi/dT=-6.0×10−4 eV/K was determined from transmission measurements in the temperature range of 10-300 K. The absolute zero value of the band gap energy was obtained as Egi(0)=2.44 eV. The dispersion of the refractive index is discussed in terms of the Wemple-DiDomenico single-effective-oscillator model. The refractive index dispersion parameters: oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index were found to be 4.87 eV, 26.77 eV, 8.48×1013 m−2 and 2.55, respectively. 相似文献
15.
V.M. Mikoushkin 《Applied Surface Science》2011,257(11):4941-4944
Nitridation of GaAs (1 0 0) by N2+ ions with energy Ei = 2500 eV has been studied by Auger- and Electron Energy Loss Spectroscopy under experimental conditions, when electrons ejected only by nitrated layer, without contribution of GaAs substrate, were collected. Diagnostics for quantitative chemical analysis of the nitrated layers has been developed using the values of NKVV Auger energies in GaN and GaAsN chemical phases measured in one experiment, with the accuracy being sufficient for separating their contributions into the experimental spectrum. The conducted analysis has shown that nanofilm with the thickness of about 4 nm was fabricated, consisting mainly of dilute alloy GaAs1−xNx with high concentration of nitrogen x ∼ 0.09, although the major part of the implanted nitrogen atoms are contained in GaN inclusions. It was assumed that secondary ion cascades generated by implanted ions play an important role in forming nitrogen-rich alloy. 相似文献
16.
Ferromagnetic Ga1−xMnxAs layers (where x=1.4-3.0%) grown on (1 0 0) GaAs substrates by molecular beam epitaxy were characterized using Raman spectroscopy. As Mn is introduced into GaAs, a marked increase in disorder in the material occurs, as indicated by the growth of the disorder-allowed transverse-optical Raman line. Another important result is that as the Mn concentration in Ga1−xMnxAs increases further beyond ca. 2%, Raman-active coupled-plasmon-longitudinal-optical phonon modes arise, which signals the increasing presence of holes, and thus provides a useful tool for determining their concentration. Using the depletion-layer approach from the Raman spectroscopy data, we determined the carrier concentration for samples with x=2.2% and 3.0% was to be 7.2×1019 and 8.3×1020 cm−3, respectively. 相似文献
17.
Jiagang Wu Dingquan Xiao Jiliang Zhu Jianguo Zhu Junzhe Tan 《Applied Surface Science》2007,253(20):8365-8370
The (Pb0.90La0.10)Ti0.975O3/PbTiO3 (PLT/PT), PbTiO3/(Pb0.90La0.10)Ti0.975O3/PbTiO3 (PT/PLT/PT) multilayered thin films with a PbOx buffer layer were in situ deposited by RF magnetron sputtering at the substrate temperature of 600 °C. With this method, highly (1 0 0)-oriented PLT/PT and PT/PLT/PT multilayered thin films were obtained. The PbOx buffer layer leads to the (1 0 0) orientation of the films. The dielectric, ferroelectric and pyroelectric properties of the PLT multilayered thin films were investigated. It is found that highly (1 0 0)-oriented PT/PLT/PT multilayered thin films possess higher remnant polarization 2Pr (44.1 μC/cm2) and better pyroelectric coefficient at room temperature p (p = 2.425 × 10−8 C/cm2 K) than these of PLT and PLT/PT thin films. These results indicate that the design of the PT/PLT/PT multilayered thin films with a PbOx buffer layer should be an effective way to enhance the dielectric, ferroelectric and pyroelectric properties. The mechanism of the enhanced ferroelectric properties was also discussed. 相似文献
18.
A.V. Zenkevich Yu.Yu. Lebedinskii A.A. Timofeyev I.A. Isayev V.N. Tronin 《Applied Surface Science》2009,255(10):5355-5358
A method for the formation of Au nanocrystal (nc) arrays embedded in an ultrathin SiO2 layer in one vacuum cycle is proposed. The method is based on the co-deposition in vacuum of ∼1 nm thick uniform Si-Au amorphous layer at a specific composition ratio by Pulsed Laser Deposition on the pre-oxidized Si(1 0 0) substrate, followed by its oxidation in the glow discharge oxygen plasma at room temperature, resulting in the precipitation of Au ncs at the bottom interface and/or at the surface of the forming SiO2 layer. The capping SiO2 layer is formed by the glow discharge plasma oxidation of further deposited ultrathin Si layer. Au ncs 2-5 nm in size and with the separation of ∼3-20 nm from each other segregate during the oxidation of Au-Si mixture as evidenced by transmission electron microscopy (TEM). The evolution of Au and Si chemical state upon each step of the SiO2:nc-Au nanocomposite structure formation is monitored in situ by X-ray photoelectron spectroscopy (XPS). The metrology of nanocomposite SiO2:nc-Au structures describing the space distribution of Au ncs as a function of Au/Si ratio is presented. 相似文献
19.
The transport properties of Sr0.98La0.02SnO3−δ in the system Sr1−xLaxSnO3−δ, after which the pyrochlore La2Sn2O7 appears, were investigated over the temperature range 4.2-300 K. The oxide was found to be n-type semiconductor with concomitant reduction of Sn4+ into Sn2+. The magnetic susceptibility was measured down to 4.2 K and is less than 3×10−5 emu cgs mol−1 consistent with itinerant electron behavior. The electron is believed to travel in a narrow band of Sn:5s character with an effective mass ∼4 mo. The highest band gap is 4.32 eV and the optical transition is directly allowed. A further indirect transition occurs at 4.04 eV. The electrical conductivity follows an Arrhenius-type law with a thermal activation of 40 meV and occurs by small polaron hopping between nominal states Sn4+/2+. The linear increase of thermo-power with temperature yields an electron mobility μ300 K (2×10−4 cm2 V−1 s−1) thermally activated. The insulating-metal transition seems to be of Anderson type resulting from random positions of lanthanum sites and oxygen vacancies. At low temperatures, the conduction mechanism changes to a variable range hopping with a linear plot Ln ρ−1 vs. T−4. The photo electrochemical (PEC) measurements confirm the n-type conductivity and give an onset potential of −0.46 VSCE in KOH (1 M). The Mott-Schottky plot C−2-V shows a linear behavior from which the flat band potential Vfb=+0.01 VSCE at pH 7 and the doping density ND=1.04×1021 cm−3 were determined. 相似文献
20.
A. Gueddim 《Applied Surface Science》2007,253(17):7336-7341
Theoretical investigations of the conduction band offset (CBO) and valence band offset (VBO) of the relaxed and pseudo-morphically strained GaAs1−xNx/GaAs1−yNy heterointerfaces at various nitrogen concentrations (x and y) within the range 0-0.05 and along the [0 0 1] direction are performed by means of the model-solid theory combined with the empirical pseudopotential method under the virtual crystal approximation that takes into account the effects of the compositional disorder. It has been found that for y < x, the CBO and VBO have negative and positive signs, respectively, whereas the reverse is seen when y > x. The band gap of the GaAs1−xNx over layer falls completely inside the band gap of the substrate GaAs1−yNy and thus the alignment is of type I (straddling) for y < x. When y > x, the alignment remains of type I but in this case it is the band gap of the substrate GaAs1−yNy which is fully inside the band gap of the GaAs1−xNx over layer. Besides the CBO, the VBO and the relaxed/strained band gap of two particular cases: GaAs1−xNx/GaAs and GaAs1−xNx/GaAs0.98N0.02 heterointerfaces have been determined. 相似文献