A.; Madan, H. S.; Kirk, A. P.; et al., "Fermi level unpinning of GaSb (100) using plasma enhanced atomic layer deposition of Al2O3," Appl. Phys. Lett. 97, 143502 (2010); http:// dx

Computer simulations of mixed phase Schottky contacts have been performed to gain insight into the effects oflateral dimensions upon device behavior. As expected, lateral dimensions comparable to the Debye length of the semiconductor result in strong modification of the device characteristics that would result from independent, parallel diodes. We suggest that such effects can playa role in most experimentally obtained contacts. Current models of Schottky barrier formation typically invoke kinetics-limited chemical interactions at the metal-semiconductor interface; such effects are unlikely to be laterally uniform over macroscopic dimensions, and may well provide strong sensitivity to seemingly minor variations in preparation techniques used by different groups. We demonstrate that mixed phase contacts, with size effects, can affect ideality factors, and can also cause disagreement between C-Vand 1-V barrier heights.

The literature currently abounds with experimental studies of Schottky barrier heights of various metals upon many semiconductors. Unfortunately, these studies present some puzzling aspects: (1) Commonly, barriers determined by C–V studies are larger than barriers determined by I–V studies, and (2) Results obtained by different workers under apparently identical conditions are not always similar. A possible explanation for such effects is simply that many/most contacts experimentally achieved are in fact multiphase; these different barrier-height regions could result from variations in the metallurgical reactions assumed by many current models of Schottky barrier energetics. The different barrier heights measured by different techniques follow directly from the functional form of the relevant probes (e.g., I–V would more heavily weight a low-barrier region). The lack of reproducibility would follow from kinetic aspects of the relevant metallurgical interactions. A recent publication discusses the functional form for I–V and C–V ’’effective’’ barrier heights from mixed-phase contacts isolated from one another. These results apply directly to mixed-phase contacts only if the linear dimensions of all contact regions are large compared to the Debye length of the substrate (≊0.1 μ for 1015 silicon). In this paper, we examine the effects of contact dimensions upon equilibrium potentials (e.g., band bending) as well as transport studies to infer ’’effective’’ barrier heights for truly mixed-phase contacts of varying dimensions but fixed area ratios.

Low temperature charge transport in vanadium oxide (VOx) thin films processed using pulsed dc sputtering is investigated to understand the correlation between the processing conditions and electrical properties. It is identified that the temperature dependent resistivity ρ(T) of the VOx thin films is dominated by a Efros–Shklovskii variable range hopping mechanism [Efros and Shklovskii, J. Phys. C 8, L49 (1975)]. A detailed analysis in terms of charge hopping parameters in the low temperature regime is used to correlate film properties with the pulsed dc sputtering conditions.

Fermi-level pinning by misfit dislocations at GaAs interfaces has been investigated. n + -GaInAs was used to control the misfit dislocation density by varying of composition and epilayer thickness. Interfaces with zero or low dislocation densities are Ohmic to current flow, and become rectifying with increasing dislocation density. The "Schottky barrier height" increases with dislocation density in accordance with a simple physical model which assumes Fermi-level pinning at the dislocation. PACS numbers: 73.40.-c, 73.30.+y Recent experimental studies on the formation of Schottky barriers at III-V semiconductor surfaces and interfaces have resulted in a proliferation of theoretical models. For example, Schottky barrier formation has been described in terms of Fermi-level pinning by adatorn-induced native defects, 1 * 2 metal-induced gap states, 3 and the electronic and chemical properties of the interface metallurgy. 4 ' 5 Definitive testing of these models is complicated by the experimental difficulty of differentiating between metallurgical and structural (defect) effects at metal/III-V interfaces. In this paper we report the electrical properties of n-type GaAs interfaces having a controlled density of a certain type of structural defect: the misfit dislocation,, We have used w + -GaInAs as the "metal" and control the misfit dislocation density by varying composition and epilayer thickness. These interfaces are free of extraneous metallurgy since they are formed by relaxing strain at lattice-mismatched heterojunctions with slightly different compositions,,The dynamics of misfit dislocation formation is well known 6 and is shown schematically in Fig.