The Hall Effect MeasurementHall eff

The Hall Effect Measurement
Hall effect measurements have been valuable tools for material characterization. The Hall effect
can be observed when the combination of a magnetic field through a sample and a current along
the length of the sample creates an electrical current perpendicular to both the magnetic field and
the current, which in turn creates a transverse voltage that is perpendicular to both the magnetic
field and the current.
A Hall effect measurement system can actually be used to determine quite a few material
parameters, but the primary one is the Hall voltage (VH). Other important parameters such as
carrier mobility, carrier concentration (n), Hall coefficient (RH), resistivity, and the conductivity
type (N or P) are all derived from the Hall voltage measurement. With the addition of some other
instruments, I-V characterization curves can be created with a similar test setup.
They’re often used in characterizing thin films of these materials for solar cells/photovoltaics, as
well as organic semiconductors and nano-materials like graphene. They are equally useful for
characterizing both low resistance materials (metals, transparent oxides, highly doped
semiconductor materials.
The Van der Pauw Method
Taking Measurements
 Measurements require four ohmic contacts on the sample
 The contacts are placed on or as close to sample boundary as possible
 The contacts are infinitely small.
 The error in measurement is given by D/L
D = average diameter of contact
L = distance between contacts
 All four contacts need to be same material
Actual sheet resistance is related to these resistances by the van der Pauw formula:
In van der Pauw resistivity measurements, the current is measured on adjacent nodes and the
voltage is measured on opposing adjacent nodes: