Conventional Van Der Pauw Research Articles

Conduction and Electric Field Effect in Ultra-Thin Tungsten Films

Ultra-thin tungsten films were prepared using hotwire assisted atomic layer deposition. The film thickness ranged from 2.5 to 10 nm, as determined by spectroscopic ellipsometry and verified by scanning electron microscopy. The films were implemented in conventional Van der Pauw and circular transmission line method (CTLM) test structures, to explore the effect of film thickness on the sheet and contact resistance, temperature coefficient of resistance (TCR), and external electric field applied. All films exhibited linear current-voltage characteristics. The sheet resistance was shown to considerably vary across the wafer, due to the film thickness non-uniformity. The TCR values changed from positive to negative with decreasing the film thickness. A field-induced modulation of the sheet resistance up to $\sim 4.6\cdot 10^{-4}\,\,\text{V}^{-1}$ was obtained for a 2.5 nm thick film, larger than that generally observed for metals.

Low-temperature LPE growth and characterization of InGaAsN thick layers

Abstract This work demonstrates the possibility for low-temperature Liquid-Phase Epitaxy (LPE) growth of lattice matched to GaAs substrate dilute nitride InGaAsN layers with good crystalline quality and high Hall electron mobility. X-ray microanalysis and X-ray diffraction methods have been used to determine the composition and crystalline quality of the grown InGaAsN layers. Surface roughness is examined by atomic force microscopy. N-related local vibration modes are observed by Raman scattering. The Hall electron mobility and free carrier concentration have been measured in the temperature range 80-300K by conventional Van der Pauw method.

Structural and electrical properties of AlxIn1-xN (0.10≤x≤0.94) films grown on sapphire substrates

AlxIn1–xN films were grown on (0001) sapphire substrates by reactive radiofrequency (RF) magnetron sputtering in an ambient of Ar and N2. The XRD patterns are shown from AlxIn1–xN films grown on AlN/sapphire substrates using a wide range of magnetron power ratio settings. The wurtzite structure films have high crystal quality with full-width at half-maximum (FWHM) in the range of 0.22°–0.52°. The surface morphologies were observed by scanning electron microscopy (SEM). Raman spectra were measured on the AlxIn1–xN surfaces in a backscattering configuration at room temperature with 532 nm laser excitation and show A1(LO) bimodal behavior. Electrical resistivity and electron mobility were measured by the Hall effect method in the conventional Van der Pauw geometry at room temperature. The lowest electrical resistivity is 1 × 10−3 Ω·cm. This work suggests that reactive magnetron sputtering is a promising method for growing AlxIn1–xN films in over a large composition range.

Electrical characterization of InGaAs ultra-shallow junctions

In this study, we investigate the limitations to sheet resistance and Hall effect characterization of ultra-shallow junctions (USJs) in In0.53Ga0.47As. We compare conventional van der Pauw and Hall effect measurements with micro four-point probe (M4PP) and micro Hall effect methods. Due to the high carrier mobility of InGaAs, we extend the micro-Hall effect position error suppression method to also take geometrical magnetoresistance into account. We find that the conventional techniques fail to measure accurately on n++∕p+ USJ due to a significant leakage current, whereas the M4PP and micro Hall effect methods are able to give accurate results. Finally, we observe a significant reduction in the carrier mobility for InGaAs USJ.

Micro-four-point probe Hall effect measurement method

We report a new microscale Hall effect measurement method for characterization of semiconductor thin films without need for conventional Hall effect geometries and metal contact pads. We derive the electrostatic potential resulting from current flow in a conductive filamentary sheet with insulating barriers and with a magnetic field applied normal to the plane of the sheet. Based on this potential, analytical expressions for the measured four-point resistance in presence of a magnetic field are derived for several simple sample geometries. We show how the sheet resistance and Hall effect contributions may be separated using dual configuration measurements. The method differs from conventional van der Pauw measurements since the probe pins are placed in the interior of the sample region, not just on the perimeter. We experimentally verify the method by micro-four-point probe measurements on ultrashallow junctions in silicon and germanium. On a cleaved silicon ultrashallow junction sample we determine carrier mobility, sheet carrier density, and sheet resistance from micro-four-point probe measurements under various experimental conditions, and show with these conditions reproducibility within less than 1.5%.

Four-Terminal Measurement and Simulations for Sheet Resistance in Piezoresistive Sensing Elements

We have seen some wafers rejected with abnormally large within-wafer variation for the input resistance (Rin) of the X-ducer in the pressure sensing element. Input resistance consists of p+,p−, the resistance of aluminum lines, and its contact resistance to p+ and p−. A four-terminal measurement (FTM) is used to characterize piezoresistors for our pressure sensing elements. The purpose in using a FTM is to find which process causes this abnormally large input resistance. Good agreement has been obtained between the finite element analysis (FEA) and experimental measurement results for this FTM technique. The difference between the conventional van der Pauw method and FEA approach is also compared and presented. It is concluded that p+ variation is the major process to cause this abnormally large input resistance. This methodology was used to diagnose the process-related problem without using special test patterns. Therefore, the development cost and cycle time was significantly reduced.

An experimental set-up for in situ Hall measurements under high-energy electronirradiation for wide-bandgap materials

A dc Hall-effect apparatus, based on conventional van der Pauw specimen geometry, hasbeen developed for in situ measurements under van de Graaff electron irradiation(0.7–2.2 MeV). An associated cryostat permits ambient temperatures of 95–300 K.A key element is a flat permanent magnet of field strength 3.55 kG. Initial testmeasurements have been performed on wide-bandgap semiconductor materials, includingan HVPE-grown AlGaN/GaN heterostructure field-effect transistor structure.

Hall effect investigations of 4H–SiC epitaxial layers grown on semi-insulating and conducting substrates

Nitrogen- and aluminum-doped 4H silicon carbide epitaxial layers were grown simultaneously on semi-insulating and conducting substrates. The layers were investigated by conventional van der Pauw Hall effect measurements and for comparison also with secondary ion mass spectrometry and capacitance voltage measurements. It was found, that the carrier concentration in the layers grown on conducting substrates were overestimated by the Hall effect measurement, which leads to an underestimation of the ionization energy of the main dopant, as compared to the layer grown on semi-insulating substrates. The difference can be explained by a two-layer Hall effect model.

Characterization of deep centers in AlGaAs/InGaAs/GaAs pseudomorphic HEMT structures grown by molecular beam epitaxy and hydrogen treatment

In AlGaAs/InGaAs/GaAs PM-HEMT structures, the characterization of deep centers, the degradation in electrical and optical properties and their effects on electrical performance of the PM-HEMTs have been investigated by DLTS, SIMS, PL and conventional van der Pauw techniques. The experimental results confirm that the deep level centers correlate strongly with the oxygen content in the AlGaAs layer, the PL response of PM-HEMTs, and the electrical performance of the PM-HEMTs. Hydrogen plasma treatment was used to passivate/annihilate these centers, and the effects of hydrogenation were examined.

Theory and Realization of a Two-Layer Hall Effect Measurement Concept for Characterization of Epitaxial and Implanted Layers of SiC

AbstractEpitaxial and implanted layers are generally characterized by Hall effect measurements using a pn-junction as electrical insulation of the layer from the substrate. Due to defects, low doping concentrations or thin layers the resistivity of epitaxial or implanted layers is comparable to the resistivity of the pn-junction and the substrate. This results in inefficient electrical insulation between both regions. To be able to determine the properties of epitaxial or implanted layers even in the case of substantial leakage current we developed a two-layer Hall effect measurement concept. This concept is based on the conventional van der Pauw technique applied to the layer and the substrate separately. In addition the current-voltage characteristic of the pn-junction is measured and modeled in the analysis as an ohmic resistor.This two-layer concept is applied to epitaxial grown SiC and the results are compared with conventional van der Pauw technique. In addition both techniques are compared with the results of capacitance-voltage (CV) measurements and secondary ion mass spectroscopy (SIMS).

An Experimental Study of Various Cross Sheet Resistor Test Structures

Newly designed cross sheet resistors are shown to give the same (within 0.5%) measured sheet resistance as conventional van der Pauw structures. Diffused boron and phosphorus layers with sheet resistances near 200 Ω/□ were studied with the sampled areas varying from a square 6.4 μm (0.25 mil) on a side to a circle 762 μm (30.0 mils) in diameter. An increase in measured sheet resistance values was observed due to surface leakage currents, and an equivalent circuit model was developed to explain the results. The effect of joule heating on measured sheet resistance values was observed in both large and small cross structures.