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Number 2475 Application Note Four-Probe Resistivity and Hall Voltage Series Measurements with the Model 4200-SCS Introduction Semiconductor material research and device testing often involve deter- Current mining the resistivity and Hall mobility of a sample. The resistivity of Source semiconductor material is primarily dependent on the bulk doping. In a device, the resistivity can affect the capacitance, the series resistance, and the threshold voltage. Voltmeter The resistivity of the semiconductor is often determined using a four-point probe technique. With a four-probe, or Kelvin, technique, two of the probes are used to source current and the other two probes are used to measure voltage. Using four probes eliminates measurement errors due to the probe resistance, the spreading resistance under each probe, and the contact resistance between each metal probe and the semiconductor material. Because a high impedance voltmeter draws little Figure 1. Four-Point Collinear Probe Resistivity Configuration current, the voltage drops across the probe resistance, spreading resist- ance, and contact resistance are very small. Two common Kelvin techniques for determining the resistivity of Using the Model 4200-SCS to Make Four- a semiconductor material are the four-point collinear probe method Point Collinear Probe Measurements and the van der Pauw method. The Model 4200-SCS Semiconductor The Model 4200-SCS can make four-point collinear probe measurements Characterization System can be used for both. Because of its high input using either three or four SMUs (source-measure units). When using impedance (>1016W) and accurate low current sourcing, the Model 4200- three SMUs, all three SMUs are set to Current Bias (voltmeter unit). SCS with preamps is ideal for high resistance samples. This application However, one SMU will source current and the other two will be used note explains how to make resistivity measurements of semiconductor to measure the voltage difference between the two inner probes. An materials using the Model 4200-SCS. example of how this can be set up with the Model 4200-SCS is shown in Figure 2. One SMU (SMU1) and the GNDU (ground unit) are used to The Four-Point Collinear Probe Method