Inhomogeneous Schottky Barrier Research Articles

Electron transport at Au/InP interface with nanoscopic exclusions

We present an investigation of electron transport at the Au/InP metal semiconductor (MS) interface in the presence of nanoscopic barrier inhomogeneities. In particular, we focus on the transport regime wherein the low barrier inhomogeneous regions are pinched off by the depletion potential of the surrounding higher barrier region. To realize this, we have fabricated a composite MS structure comprising of a known density of nanometer sized Ag aerosol particles on InP overlayed by a uniform Au film. Temperature dependent current–voltage (I–V) measurements were performed to characterize the electron transport at the composite MS interface. The experimental observations are explained using a simple model for the MS junction current in which the Ag/InP regions are assumed to be identical and noninteracting. Our results clearly demonstrate that the electron transport at the MS interface is significantly affected by low barrier regions even in the pinch-off regime. In addition, the influence of the particle density and the Ag/InP barrier heights on the diode characteristics is also investigated. It is suggested that Schottky barrier inhomogeneities could be the main source of the usually observed larger-than-unity ideality factors in diodes. Furthermore, our results indicate possibilities of using such composites to explore the physics and applications of nanoinjecting contacts.

Electrical transport in (100)CoSi2/Si contacts

A detailed investigation of the electrical transport in (100) CoSi2/Si contacts is presented. The transport properties of epitaxial CoSi2 films, obtained both by ion-beam synthesis and by solid-state reaction of a Ti/Co bimetallic layer, are compared with the transport properties of conventional polycrystalline CoSi2 layers. The electrical resistivity, the magnetoresistance, and the Hall effect are measured on Hall bars for temperatures ranging from 1.2 to 300 K and magnetic fields up to 5 T. Very high values of the order parameter kFL0 are observed, indicating that the investigated samples are of very high purity and crystalline order. In addition, the electric transport at the CoSi2/Si interface is studied by current-voltage and capacitance-voltage measurements on Schottky diode structures for temperatures ranging from 173 to 333 K. Ideality factors close to unity are observed for the highest temperatures, for the lower temperatures the ideality factors are found to increase with decreasing temperatures. The observed temperature dependence of the ideality factor and the Schottky barrier height can be attributed to Schottky barrier inhomogeneities.

Schottky barrier inhomogeneities in Au-Ni and Au-Cr contacts to InP-ohmic contact applications

The electrical transport properties of carriers (electrons) across the metal-semiconductor interface for Au/Ni/Au and Au/Cr/Au contacts to n-type InP have been compared. It is found that the interfacial properties are complex with many possible phases at the interface. The electrical properties of the contacts can be described in terms of Schottky barrier inhomogeneities at the interface and a parallel conduction model applies. From this model it is found that the observed reduction in the contact resistance is closely connected to a lowering of the effective Schottky barrier towards 0 eV.

Electron transport of inhomogeneous α-FeSi 2/(111)Si Schottky barriers

Continuous buried layers of metallic α-FeSi 2 were fabricated by Ion Beam Synthesis in (111)Si substrates. Laterally patterned α-FeSi 2 Schottky diodes with different areas were fabricated by implantation through an SiO 2 mask. While diode characteristics were only observed on n-type Si, on p-type Si nearly ohmic behaviour was observed. The analysis of I– V curves indicated a strong temperature dependence; in the high temperature range between 360 and 420 K, the contacts showed nearly ideal behaviour with ideality factors n ⩽ 1.1 and an exceptionally high Schottky barrier height of Φ B = 0.96 ± 0.02 eV. At lower temperatures we observed non-ideal behaviour of the electron transport through the α-FeSi 2/(111)Si interfaces, revealed by ideality factors larger than 1 and a bias-dependence of the effective Schottky barrier height Φ eff. All effects can be attributed to Schottky barrier inhomogeneities.

Electron transport of inhomogeneous Schottky barriers

A novel approach is presented which leads to analytic solutions to the potential and the electron transport through inhomogeneous Schottky barriers. The existence of barrier height nonuniformities is shown to provide a simple explanation of the following abnormal experimental results, routinely observed from various Schottky barriers: greater-than-unity ideality factors, the T0 effect, the ‘‘soft’’ reverse characteristics, and the dependence of barrier height on the technique of measurement.