Papers by Keyword: Schottky Barrier

Abstract: This paper reports on the effect of a sulfurization thermal process of the silicon carbide surface on the properties of Ni/4H-SiC Schottky barrier. In particular, the incorporation of sulfur (S) in the 4H-SiC near-surface region was observed at the process performed at 800 °C, without any significant effect on the surface morphology. On the other hand, Ni/4H-SiC Schottky contacts fabricated on the sulfurized 4H-SiC surface showed a 0.3 eV reduction of the average barrier height with a narrower distribution, with respect to the untreated sample. These results were explained by an increase of the 4H-SiC electron affinity after sulfurization, and a Fermi level pinning effect.

Abstract: In this manuscript Ohmic contact formation at low annealing temperatures is demonstrated using shallow implantation technique. Remarkably, Ni Ohmic contacts with a specific contact resistivity of 1.9x10^-5 Ωcm² have been achieved at as-deposited condition. Smooth interfaces along with reduced Schottky barrier at the metal/SiC interface contributed to improved Ohmic performance at as-deposited and 450°C anneal conditions.

Abstract: Characterization of electrical parameters of Copper Phthalocyanine dye has been done in the present work. In the context of electrical parameters, the Schottky barrier and ideality factor of the organic device has been measured and the effects of fullerene nanoparticles on these parameters have been studied. Analysis of electrical parameters has been done by the current-voltage characteristics of the device. The influence of fullerene nanoparticles lessens the Schottky barrier to 0.71 eV from 0.75 eV. The current flow is assumed to be injection limited as the Schottky barrier is greater than 0.3 eV - 0.4 eV. The Schottky barrier is also estimated by the Norde method. Norde's method shows lessening of barrier height from 0.70 eV to 0.65 eV under the influence of fullerene nanoparticles. The measured ideality factor value reduces from 3.787 to 1.495 in presence of fullerene nanoparticles. The charge injection mechanism at metal-organic contact gets influenced by the interfacial Schottky barrier height. Decrease in both Schottky barrier and ideality factor attribute to the increase in charge flow and it allows a reduction in the device’s transition voltage from 2.5 V to 1.0 V.

Abstract: In this paper we will present the results of repetitive surge stress carried out on six 3.3 kV-5A Ti/Ni 4H-SiC JBS diodes. Repetitive current peaks between 10 A and 24 A have been applied and some diodes were able to endure 100,000 cycles while others failed before. The causes of failure have not been determined but a correlation between peak surge current and physical parameters evolution rate has been proven. Simulations show that contact temperature during surge can reach 300 °C, which is very close to Schottky contact annealing temperatures.

Abstract: The electrical contact properties of silicon carbide (SiC) and carbon nanotubes (CNTs) were measured by conductive atomic force microscopy (C-AFM). A CNT forest was synthesized by SiC surface decomposition. Trenches, which electrically separate the conduction area, were fabricated using a focused ion beam (FIB) without a cover layer, and the resistance of each island was measured by C-AFM. From the dependence of the resistance on the CNT forest island size, the contact resistance between the CNTs and the SiC substrate was measured. By varying the dopant density in the SiC substrate, the Schottky barrier height was evaluated to be ~0.5 eV. This is slightly higher than a previously reported result obtained from a similar setup with a metal covering the CNT forest. We assumed that the damaged region existed in the islands, which is due to the trench formation by the FIB. The commensurate barrier height was obtained with the length of the damaged region assumed to be ~3 μm. Here, we could estimate the resistivity of a CNT/SiC interface without a cover layer. This indicates that a CNT forest on SiC is useful as a brief contact electrode.

Abstract: Literature data on the effective electrical injectors of electron spin for silicon spintronics and stages of the investigation of corresponding magnetic tunnel contacts are reviewed up to 2015 year and a consideration of the current state of the research is given. Different structures for the spin injection, materials and possible applications in silicon spintronics are considered and also possible future research directions are outlined.

Abstract: Surface states have hindered and degraded many semiconductor devices since the Bardeen era. Surface states originate from dangling bonds on the surface. This paper discusses a generic solution to surface states, i.e. valence-mending passivation. For the Si (100) surface, a single atomic layer of valence-mending sulfur, selenium or tellurium can terminate ~99% of the dangling bonds, while group VII fluorine or chlorine can terminate the remaining 1%. Valence-mending passivation of Si (100) has been demonstrated using CVD, MBE and solution passivation. The keys to valence-mending passivation include an atomically-clean Si (100) surface for passivation and precisely one monolayer of valence-mending atoms on the surface. The passivated surface exhibits unprecedented properties. Electronically the Schottky barrier height between various metals and valence-mended Si (100) now follows more closely the Mott-Schottky theory. With metals of extreme workfunctions, new records for low and high Schottky barriers are created on Si (100). The highest barrier so far is 1.14 eV, i.e. a larger-than-bandgap barrier, and the lowest barrier is below 0.08 eV and potentially negative. Chemically silicidation between metal and valence-mended Si (100) is suppressed up to 500 °C, and the thermally-stable record Schottky barriers enable their applications in nanoelectronic, optoelectronic and photovoltaic devices. Another application is transition metal dichalcogenides. Valence-mended Si (100) is an ideal starting surface for growth of dichalcogenides, as it provides only van der Waals bonding to the dichalcogenide.

Abstract: We report on the electrophoretic deposition (EPD) of metal nanoparticles (NPs) prepared in reverse micelles on semiconductor substrates with the aim to fabricate sensitive Schottky-based hydrogen sensors with fast response and high degree of selectivity. We discuss the mechanism of NP monolayer formation and show which parameters are essential for the transition from three-dimensional to two-dimensional growth.

Abstract: The magnetic and electrical properties of (Co/Ge)_nfilms are experimentally studied. It is established that at the Co/Ge interfacean intermediate magnetic layer forms. Twophases of cobalt, one is a face-centered cubic phase and the other ispresumably a Co–Ge alloy with a weakly ferromagnetic order, have been found toexist. A “dead” layer no more than 2 nm in thickness is formed at the interface.This layer affects the magnetic behavior andmagnetoresistive effect in the investigated structures.

Abstract: The electrical properties of the interface between quasi free standing bilayer graphene (QFBLG) and SiC(0001) have been investigated by nanoscale resolution current measurements using conductive atomic force microscopy (CAFM). I-V analyses were carried out on Au-capped QFBLG contacts with different sizes (from 200 down to 0.5 μm) fabricated on SiC samples with different miscut angles (from on-axis to 3.5° off-axis). The extracted QFBLG/SiC Schottky barrier height (SBH) was found to depend on the contact size. SBH values ∼0.9-1 eV were obtained for large contacts, whereas a gradual increase was observed below a critical (micrometer scale) contact size (depending on the SiC miscut angle) up to values approaching ∼1.5 eV. Nanoscale resolution current mapping on bare QFLBG contacts revealed that SiC step edges and facets represent preferential current paths causing the effective SBH lowering for larger contacts. The reduced barrier height in these regions can be explained in terms of a reduced doping of QFBLG from SiC substrate at (11-20) step edges with respect to the p-type doping on the (0001) terraces.