Holmarc's Hall Effect apparatus (Model no: HO-ED-EM-06) is designed with state of the art modules and components. Digital display is used for all value read outs. Electromagnets, gauss meter, power supply, etc. are designed and made as separate modules for students to understand the apparatus and the principles involved easily. Safety is given due consideration in the design of the apparatus
The system consists of two cartridges, each of which is equipped with 'p' and 'n' doped germanium crystal .The cartridges can be plugged easily and safely into the D connector system. The Hall Effect set up provides all operating parameters for the samples and displays the Hall voltage, sample current as well as the sample temperature. The doped Germanium samples are used to measure the Hall-voltage as a function of the sample current, the magnetic flux density and the sample temperature.
The Hall voltage is caused by the deflection of the moving charge carriers in the magnetic field due to the Lorentz force, of which, direction can be predicted by the right hand rule. The sign of the Hall coefficient is determined by the polarity of the charge carriers: a negative sign implies carriers with a negative charge ("normal Hall effect"), and a positive sign indicates carriers with a positive charge ("anomalous Hall effect"). The Hall coefficient depends on the material and the temperature.
Introduce the gauss meter probe between the poles of electromagnet. Change the current from zero up to its maximum value and from maximum to zero. Note the corresponding field strength from gauss meter at different intervals. Plot a graph Magnetic field Vs Current.
Electrons in a semiconductor only become available for conduction when they acquire enough thermal energy to reach a conduction state; this makes the carrier concentration highly dependent on temperature.
Connect the sample control probe to Hall Effect Control and turn on the Hall Effect set up. Vary the sample current from zero up to its maximum value in equal intervals. Note the corresponding Hall voltage readings. Plot the graph, Hall voltage as a function of the sample current.
We get Carrier Density from the equation,
n = [ 1 / ( RH e ) ] c m3
We get Carrier Mobility from the equation,
µ = RH . σ c m2 Volt-1 sec-1
where σ is the conductivity of material
The Hall voltage VH is caused by the deflection of the moving charge carriers in the magnetic field due to the Lorentz force, whose direction may predicted by the right hand rule. The factor 1 / ( ne ) is called Hall coefficient RH.
RH = ( VH / B ) x ( d/IH ) c m3 Coulomb-1
B - Magnetic flux density
IH - Current through the semi conductor
d - Thickness of the conductor
n - Concentration of charge carriers