M91 FastHall measurement controller applications

Fast — ideal for low mobility materials

Hall effect measurement is a key step in characterizing the transport properties of novel electronic materials and devices. It is commonly performed using the traditional DC field method, requiring little more that a stable current source, a voltmeter, a switch and a magnet and is relatively straightforward and reliable for simpler materials with higher mobilities. However, the difficulty increases and accuracy of measurement decreases as material mobilities decrease. This is often the case in promising new semiconductor materials such as photovoltaics, thermoelectrics, and organics.

For the past several years, AC field techniques using advanced lock-in amplifiers and longer measurement windows to extract smaller Hall voltage signals have been used to explore these materials. But extended measurement intervals can also add new forms of error from thermal drift effects. And, of course, results take longer to get, sometimes many hours for very low mobility materials.

The FastHall technique eliminates both of these issues— it accurately measures even extremely low mobility materials in seconds.

Hall voltage

  • Resolution = 1 µV
  • Noise = 0.1 µV (RMS), averaged over 1 power line cycle

Resistance/resistivity (four-contact in-line probe and van der Pauw)

  • Calculated by instrument
  • Resistance range 100 µΩ to 10 MΩ standard; up to 200 GΩ with high-resistance option

Magnetoresistance

  • System provides field control to measure resistance as a function of magnetic field; ΔR/Ro data is plotted and measured values are saved to file

Hall coefficient

  • Calculated by instrument
  • Derived from Hall voltage, magnetic field, and current

Hall mobility

  • Calculated by instrument
  • 10-3 to 106 cm2/V s

Anomalous Hall effect (AHE)

  • System provides field control to measure Hall voltage as a function of magnetic field; Hall voltage data is plotted as function of magnetic field and saved to file

Carrier type/concentration/density

  • Sheet or volume carrier concentration calculated
  • Sheet carrier density ≤1017 cm-2

 

M91 overview

More about the M91