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.

Van-der-Pauw measurement on devices with four contacts and two orthogonal mirror symmetries

Abstract: Resistive thin film devices with four contacts of arbitrary size are discussed analytically by conformal mapping and equivalent resistor circuit. The device symmetry is assumed to be mirror symmetric to two lines, which are perpendicular. These lines go either through the contacts or midway between the contacts. This limits the degrees of freedom (DoF) to three. It is shown how to derive the sheet resistance and the other two DoF by Van-der-Pauw measurement without knowledge of the specific device geometry. It is also elucidated why conventional Van-der-Pauw method fails for devices with large contacts – an alternative procedure is proposed. The results are applicable to Van-der-Pauw devices, Hall plates, Vertical Hall effect devices, and mechanical stress sensors.

Improved quality GaN films grown by molecular beam epitaxy on sapphire

Abstract: We report on the epitaxial growth and characterization of gallium nitride by molecular beam epitaxy (MBE). The samples were grown on (0002) sapphire using solid metal group III sources and an EPI UniBulb™ rf plasma source to produce atomic neutral nitrogen species. The films were characterized optically using reflectance and photoluminescence, van der Pauw Hall effect measurements, and x-ray rocking curves for the (0002), (1014), and (2204) directions. Nominally undoped films were grown with a (0002) rocking curve (ω) full width at half maximum (FWHM) from 700 to 125 arcsec, electron mobilities of up to 180 cm2/V s, and background carrier concentrations from the mid- 1017–2×1016/cm3. The room temperature photoluminescence FWHM for these films ranged from 38 up to 62 meV, with peak to yellow ratios from 7 to 70. These values represent an improvement in the quality of nominally undoped heteroepitaxially grown GaN by MBE.

High temperature Hall‐effect apparatus

Abstract: A high‐temperature Hall‐effect apparatus is described which allows measurements up to temperatures greater than 1200 K using the van der Pauw method. The apparatus was designed for measurements on refractory materials having high charge carrier concentrations and generally low mobilities. Pressure contacts are applied to the samples. Consequently, special contacting methods, peculiar to a specific sample material, are not required. The apparatus has been semiautomated to facilitate measurements. Results are presented on n‐ and p‐type silicon.

Study of Implantation Defects in CVD Graphene by Optical and Electrical Methods

Abstract: A Chemical Vapor Deposition graphene monolayer grown on 6H–SiC (0001) substrates was used for implantation experiments. The graphene samples were irradiated by He+ and N+ ions. The Raman spectra and electrical transport parameters were measured as a function of increasing implantation fluence. The defect concentration was determined from intensity ratio of the Raman D and G peaks, while the carrier’s concentration was determined from the relations between G and 2D Raman modes energies. It was found that the number of defects generated by one ion is 0.0025 and 0.045 and the mean defect radius about 1.5 and 1.34 nm for He+ and N+, respectively. Hole concentration and mobility were determined from van der Pauw measurements. It was found that mobility decreases nearly by three orders of magnitude with increase of defect concentration. The inverse of mobility versus defect concentration is a linear function, which indicates that the main scattering mechanism is related to defects generated by ion implantation. The slope of inverse mobility versus defect concentration provides the value of defect radius responsible for scattering carriers at about 0.75 nm. This estimated defect radius indicates that the scattering centres most likely consist of reconstructed divacancies or larger vacancy complexes.