Van der Pauw method

About: Van der Pauw method is a research topic. Over the lifetime, 1682 publications have been published within this topic receiving 25364 citations.

N-Polar InAlN/AlN/GaN MIS-HEMTs

Abstract: N-polar metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) were fabricated from a GaN/AlN/InAlN/GaN heterostructure grown by metalorganic chemical vapor deposition on a vicinal sapphire substrate, using Si3N4 as the gate insulator. Hall measurements in van der Pauw geometry on the heterostructure showed a sheet charge density and a mobility of 2.15 × 1013 cm-2 and 1135 cm2·V-1·s-1, respectively. Resistance measurements revealed anisotropic conductivity with respect to the surface steps induced by the substrate misorientation, and the sheet resistance of the 2-D electron gas was as low as 226 Ω/□ in the parallel direction. MIS-HEMTs with a gate length of 0.7 μm and a source-drain spacing of 2.2 μm had a peak drain current of 1.47 A/mm and an on-resistance of 1.45 Ω·mm. At a drain bias of 8 V, the current- and power-gain cutoff frequencies were 14 and 25 GHz, respectively.

Defects and transport in Gd-doped BaPrO3

Abstract: The electrical conductivity of BaPr1−x GdxO3−δ has been characterized by means of the four-point van der Pauw technique at 200–1100 °C as a function of pO2 and pH2O. The contributions from ionic charge carriers were investigated by the EMF of concentration cells and the H+/D+ isotope effect on the total conductivity. BaPr1−x Gd x O3−δ is predominately a p-type electronic conductor under oxidizing conditions, while ionic conduction is barely measurable. Gd(III) substituted for Pr(IV) is charge compensated mainly by electron holes, with protons and oxygen vacancies contributing significantly but as minority defects only at low temperatures (wet conditions) and at high temperatures, respectively. The conductivity behaviour has been modelled under these assumptions to extract thermodynamic parameters for the defect reactions at play. The practical use of this material is limited by its poor chemical stability.

The effect of Fe content in electrodeposited CoFe/Cu multilayers on structural, magnetic and magnetoresistance characterizations.

Abstract: A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control, but the Fe concentration in the electrolytes was changed from 0.0125 M to 0.2 M. The deposition was carried out in a three-electrode cell at room temperature. The deposition of Cu layers was made at a cathode potential of -0.3 V with respect to saturated calomel electrode (SCE), while the ferromagnetic CoFe layers were deposited at -1.5 V versus SCE. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure. The magnetic characteristics of the films were investigated using a vibrating sample magnetometer and their easy-axis was found to be in film plane. Magnetoresistance measurements were carried out using the Van der Pauw method at room temperature with magnetic fields up to +/- 12 kOe. All multilayers exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained.

Crystal orientation dependence of the electrical transport and lattice structure of zinc selenide films grown by metalorganic chemical vapor deposition

Abstract: ZnSe films have been grown on 〈100〉, 〈110〉, and 〈111〉B GaAs surfaces, using the metalorganic chemical vapor deposition technique. The electrical transport properties and lattice structure characteristics of these films have been studied using a van der Pauw technique and high‐resolution transmission electron microscopy. The electrical and structural properties of these films vary significantly with growth direction. In (100) layers, the observed defects are similar in nature to isolated compensated centers. For other orientations, observed properties are best described in terms of extended defects and grain boundaries.