Extracted Barrier Height Research Articles

Effect of annealing temperature on electrical and structural properties of transparent indium tin oxide electrode to n-type GaN

The effects of thermal annealing temperature on electrical, structural and surface morphology characteristics of transparent indium tin oxide (ITO) electrode to n-type gallium nitride (GaN) have been investigated. The Schottky barrier height of as-deposited ITO/n-GaN is found to be 0.61 eV ( I– V) 0.64 eV ( C– V). The extracted barrier heights of ITO/n-GaN annealed contacts are 0.67 eV ( I– V) 0.71 eV ( C–V) at 200 °C, 0.70 eV ( I–V) 0.75 eV ( C–V) at 300 °C, and 0.72 eV ( I–V) 0.78 eV ( C–V) at 400 °C, respectively. Annealing at 500 °C for 1 min in the nitrogen ambient, increases the barrier height and the corresponding values are 0.74 eV ( I–V) 0.83 eV ( C–V). The Norde method was also used to extract the barrier height of ITO/n-GaN Schottky contacts. From the above observations, it is clear that the electrical properties of annealed ITO contacts are improved compared to the as-deposited films. Based on the Auger electron spectroscopy and X-ray diffraction results, the formation of gallide phases at the ITO/n-GaN interface could be the reason for the improvement of electrical properties upon annealing at various temperatures. The measured transmittance of ITO films between 380 nm and 450 nm is above 90% for a sample annealed at 500 °C. Atomic force microscopy results showed that the surface morphology of a contact annealed at 500 °C is fairly smooth with a RMS roughness of 2.37 nm.

Schottky Barrier Height Extraction in Ohmic Regime: Contacts on Fully-Processed 200mm GeOI Substrates

The problematics of contacts optimization on Germanium MOSFETs suffers from a gap between fundamental studies and the structures obtained after full processing. The contact properties of metals such as Ti on Ge were so far mostly investigated on weakly n-doped samples under pure Thermionic Emission (TE) regime. In this paper, we detail Schottky Barrier Height (SBH) extractions based on contact resistance (Rco) measurements on highly n- and p-doped Ge, where the predominant tunnel current component results in ohmic behavior. We applied this methodology to our fully-processed GeOI samples with Ti-based contacts, yielding effective barriers of 0.32eV for electrons and 0.15eV for holes. The method provides a good physical understanding of the technological factors impacting their electrical properties, therefore enabling to define paths towards ohmic contact optimization in the context of device integration on GeOI.

Schottky Barrier Height Extraction in Ohmic Regime: Contacts on Fully-Processed 200mm GeOI Substrates

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DNA Sensing by Field-Effect Transistors Based on Networks of Carbon Nanotubes

We report on the sensing mechanism of electrical detection of deoxyribonucleic acid (DNA) hybridization for Au- and Cr-contacted field effect transistors based on single-walled carbon nanotube (SWCNT) networks. Barrier height extraction via low-temperature electrical measurement provides direct evidence for the notion that the energy level alignment between electrode and SWCNTs can be affected by DNA immobilization and hybridization. The study of location-selective capping using photoresist provides comprehensive evidence that the sensing of DNA is dominated by the change in metal-SWCNT junctions rather than the channel conductance.

Schottky contact barrier height extraction by admittance measurement

Different from the conventional current-voltage and capacitance-voltage methods, Schottky contact barrier height extraction by admittance measurement is proposed and discussed in this paper. In this method, the barrier height can be simply extracted from the difference between the measured admittance at zero bias and a reasonably high forward bias. Both simulation results and experimental data demonstrate that the proposed method is effective not only for extraction of Schottky contacts with higher barrier heights (>0.4eV) but also for extraction of those with moderately lower barrier heights (0.2–0.4eV).

Temperature Dependence of the Tunnel-Emission Conduction Current in Metal- ZrO2-Silicon Capacitor Structures

Zirconium oxide is considered as a potential replacement for due to its high dielectric constant. The metal-insulator-semiconductor capacitors were fabricated. The electrical conduction mechanism in zirconium oxide thin films as a function of temperature and electric field was studied. The temperatures measured were and from . With the Al electrode under negative bias, the conduction mechanism in the electric field of and at the temperature is found to be Fowler-Nordheim tunneling emission. The extracted barrier height between Al and is . At the electric field of and temperatures of , the electrical conduction is dominated by tunnel emission of trapped electrons with an extracted trap barrier height of at . The trap barrier height decreases as the temperature increases. This barrier height decreases linearly with temperature with a slope of about . The lowering of the barrier height is explained by bandgap reduced with increasing temperature.

Measurement of low Schottky barrier heights applied to metallic source/drain metal–oxide–semiconductor field effect transistors

This article investigates the extraction of low Schottky barrier heights in the perspective of integration of metal–oxide–semiconductor field effect transistors (MOSFET) with a metallic source/drain. A test structure composed of two back-to-back junctions is proposed to characterize materials with a low Schottky barrier. To complete the proposed measurement setup, particular attention is placed on a Schottky transport model that continuously combines thermionic emission, field emission, and barrier lowering due to image charge. In the case of platinum silicide (PtSi) contact, it is shown that Arrhenius plots can be accurately reproduced over a wide range of temperature and applied bias. A consolidation of the measurement strategy and of the associated transport model is also performed through measurements and simulations on a long channel p-type Schottky barrier silicon-on-insulator MOSFET with PtSi source/drain. A excellent agreement between simulated and experimental current-voltage characteristics is obtained for a zero-field barrier height of 0.14 eV consistent with the value (0.145 eV) that best fits the Arrhenius plot measured on test structures. The corresponding bias-dependent effective barrier height in the 0.11–0.12 eV range is therefore confirmed at the device level.

InAs/GaP/InGaP high-temperature power Schottky rectifier

An InAs/GaP/InGaP rectifier has been fabricated using a semiconductor-semiconductor “Schottky” junction to utilize the thermal stability of the semiconductor-semiconductor interface. The InAs/GaP/InGaP system demonstrates rectifying characteristics with an ideality factor of 2.3 and a current–voltage extracted barrier height of 0.96 eV. It exhibits low reverse bias leakage current and achieves breakdown electric field of 0.6 MV/cm. The InAs/GaP/InGaP system maintains the rectifying characteristics up to 600 °C. Further improvement of the thermal stability is expected to be achieved by reducing the diffusion of Si dopant atoms across the InAs/GaP interface at high temperature.

Electrical characterization and modeling of MOS structures with an ultra-thin oxide

Ultra-thin oxides (1–3 nm) are foreseen to be used as gate dielectric in CMOS technology during the next 10 years. Nevertheless, they require new approaches in modeling and characterization due to the onset of quantum effects (confinement and direct tunneling). In this paper, the modeling of quantum effects is briefly reviewed, underlining recent results. An original method to extract the oxide thickness from C– V measurement without using time-consuming simulation is proposed. Moreover an analytical model for the gate current in the inversion regime is developed based on the concept of impact frequency and within the variational approach for quantum confinement. Finally, a new experimental procedure for effective mass and barrier height extraction in thin oxides is presented.

Conduction Mechanisms in SrTiO3 Thin Films on Silicon

ABSTRACTNew materials with high dielectric constant are currently being explored to replace silicon dioxide as gate dielectric for device scaling below 0.1 μm. With respect to conventional SiO2, these high permittivity dielectrics provide the required equivalent oxide thickness (EOT) without of further reduction of the insulator physical thickness, which is a key issue to limit gate leakage current and to maintain comparable MOSFET operation and reliability. The present paper presents preliminary results on conduction mechanisms in thin epitaxial SrTiO3 films grown by MBE on Si (100). I-V measurements were performed on Al/STO/Si structures at temperatures ranging from 40 K to 290 K. At temperatures lower than 100 K the conduction mechanism of electrons from gate electrode across the oxide barrier neither Schottky emission nor tunneling. For temperatures higher than 100 K Schottky emission occurs and barrier heights were extracted, showing an approximate linearly increase with temperature. In case of Si/STO interface, a Fowler-Nordheim tunneling mechanism was detected at 40 K and at intermediate fields. The extracted barrier heights are: 0.07 eV at Si/STO interface and from 0.26 eV (130 K) to 0.53 eV (290 K) at Al/STO interface.

Conduction Mechanisms in SrTiO3 Thin Films on Silicon

ABSTRACTNew materials with high dielectric constant are currently being explored to replace silicon dioxide as gate dielectric for device scaling below 0.1 μm. With respect to conventional SiO2, these high permittivity dielectrics provide the required equivalent oxide thickness (EOT) without of further reduction of the insulator physical thickness, which is a key issue to limit gate leakage current and to maintain comparable MOSFET operation and reliability. The present paper presents preliminary results on conduction mechanisms in thin epitaxial SrTiO3 films grown by MBE on Si (100). I-V measurements were performed on Al/STO/Si structures at temperatures ranging from 40 K to 290 K. At temperatures lower than 100 K the conduction mechanism of electrons from gate electrode across the oxide barrier neither Schottky emission nor tunneling. For temperatures higher than 100 K Schottky emission occurs and barrier heights were extracted, showing an approximate linearly increase with temperature. In case of Si/STO interface, a Fowler-Nordheim tunneling mechanism was detected at 40 K and at intermediate fields. The extracted barrier heights are: 0.07 eV at Si/STO interface and from 0.26 eV (130 K) to 0.53 eV (290 K) at Al/STO interface.

C– V dependence of inhomogeneous Schottky diodes

We have studied the C– V dependence of inhomogeneous Schottky diodes by numerical simulation using Poisson's equation and the current continuity equations under the assumption of quasi-static approximation. Inhomogeneous barriers were modelled by a Gaussian barrier height distribution with two different space distributions of particular patches with different barrier heights. The results are compared with the simulations of homogeneous diodes. As expected, only a small difference has been found between the reverse bias C– V curves and the extracted barrier height of homogeneous diodes and inhomogeneous diodes simulated with the mean barrier height of the inhomogeneous diode equal to the barrier height of the homogeneous diode. A capacitance peak was observed for both cases in forward bias. The homogeneous and inhomogeneous diodes differ in the peak height.

Schottky barrier heights of Pt and Ir silicides formed on Si/SiGe measured by internal photoemission

Lowered-barrier-height silicide Schottky diodes are desirable for obtaining longer cutoff-wave- length Si-based infrared detectors. Silicide Schottky diodes have been fabricated by the reaction of evaporated Pt and Ir films on p-Si1−xGex alloys with a thin Si capping layer. The onset of metal-SiGe reactions was controlled by the deposited metal thickness. Internal photoemission measurements were made and the barrier heights were obtained from these. Pt-SiGe and Ir-SiGe reacted diodes have barrier heights of ∼0.27 and ∼0.31 eV, respectively, higher than typical values of 0.22 and 0.12 eV for the corresponding silicide/p-Si diodes. Their emission constants are also lower and more voltage dependent than silicide/Si diodes. PtSi/Si/SiGe diodes, on the other hand, have lower barrier heights (∼0.15 eV) than the PtSi/Si barrier height. The barrier height shifts in such silicide/Si/SiGe diodes are interpreted by accounting for tunneling through the unconsumed Si layer. This is done analytically using a simple model based on the Cohen, Vilms, and Archer (unpublished) modification to the Fowler equation, and leads to an extracted barrier height, that is, the Si barrier height reduced by the Si/SiGe band offset.

Kinetic isotope effect in direct ethane dissociation on Pt(111)

Supersonic molecular beam techniques were used to study the dynamics of direct C 2H 6 and C 2D 6 dissociation on Pt(111). The initial dissociation probabilities for both isotopes, S 0(C 2H 6 and S 0(C 2D 6), increased with normal translational energy, E n, over the entire range of E n studied. A significant normal kinetic isotope effect was observed; the ratio S 0(C 2H 6/ S 0(C 2D 6) decreased from 2.7 to 1.6 as E n was increased from 80 to 118 kJ mol . A one-dimensional quantum mechanical tunneling model based on an Eckart potential barrier quantitatively accounts for these observations. After correcting for translational energy dissipation to the lattice, the extracted barrier heights, V 0, and widths, L, are 123 kJ mol , 1.1 Å and 130 kJ mol , 1.1 Å for C 2H 6, and C 2D 6, respectively. The larger barrier height for the direct dissociation of C 2D 6 relative to C 2H 6 can be attributed to differences in zero point energy for C-H(D) stretching motion. Neither. S 0(C 2H 6) nor S 0(C 2D 6) exhibited a dependence on nozzle temperature in these experiments suggesting that excitation of the normal vibrational motions of methyl rocking and deformation, C-C stretching and torsion do not promote direct ethane dissociation on Pt(111) under these experimental conditions.

Kinetic isotope effect in direct ethane dissociation on Pt(111)

Supersonic molecular beam techniques were used to study the dynamics of direct C2H6 and C2D6 dissociation on Pt(111). The initial dissociation probabilities for both isotopes, S0(C2H6 and S0(C2D6), increased with normal translational energy, En, over the entire range of En studied. A significant normal kinetic isotope effect was observed; the ratio S0(C2H6/S0(C2D6) decreased from 2.7 to 1.6 as En was increased from 80 to 118 kJmol. A one-dimensional quantum mechanical tunneling model based on an Eckart potential barrier quantitatively accounts for these observations. After correcting for translational energy dissipation to the lattice, the extracted barrier heights, V0, and widths, L, are 123 kJmol, 1.1 A and 130 kJmol, 1.1 A for C2H6, and C2D6, respectively. The larger barrier height for the direct dissociation of C2D6 relative to C2H6 can be attributed to differences in zero point energy for C-H(D) stretching motion. Neither. S0(C2H6) nor S0(C2D6) exhibited a dependence on nozzle temperature in these experiments suggesting that excitation of the normal vibrational motions of methyl rocking and deformation, C-C stretching and torsion do not promote direct ethane dissociation on Pt(111) under these experimental conditions.

Effect of near-surface damage on C-V measurements of Schottky barrier diodes

During a number of current silicon technological processes used for the realization of Schottky barrier diodes, the silicon surface is bombarded by energetic particles so that deep traps are being detected in the device up to a fraction of a micron from the metal-silicon interface. The effect of such traps on the parameters, usually extracted from capacitance-voltage measurements under the form 1/ C 2 − V is studied. It is shown that the traps modify the extracted doping profile at a low reverse bias and that they have a strong effect on the extracted barrier height which can be larger or lower than the value obtained in the absence of traps, depending upon the trap characteristics. Experimental results obtained on Ti−W / nSi Schottky barrier diodes confirm these considerations.