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Measurement of Hall voltage and resistivity
Measurement of Sheet Resistivity
Measurement of Hall voltage
 V43 V14 
RA
 sheet 


 F (Q ) where Q 
2 ln 2  I12 I 23 
RB
Resistivity
   sheet t
Here, t = thickness of the sample
n sheet
 sheet
1


q
q  sheet 
Slide # 1
Variation of F with Q
F(Q) = 1, if RA = RB
Slide # 2
Summary of the Hall measurement
• For Hall measurements the magnitude of the magnetic field should
be small to avoid magneto-resistance or reduction in conductance
due to the magnetic field
• Measurement of both mobility and sheet charge density is possible
• The volume density of carriers is possible to estimate if the
thickness of the sample is known
• The sign of the charge carriers can be found from the sign of the
Hall voltage
• Advantageous for samples having 2DEG since direct measurement
of sheet charge density can be made unlike CV technique
• Hall measurement includes overall effects of both majority and
minority carriers
Slide # 3
Hall Effect sensor: Chip and Spec
ANALOG DEVICES - AD22151YRZ IC, HALL EFFECT SENSOR, LINEAR,
8-SOIC
Slide # 4
Scattering processes in bulk GaAs
•
•
•
•
•
Ionized impurity scattering
Acoustic phonon scattering
Polar optical scattering
Alloy scattering
Defect related scattering
Note that ionized impurity scattering is
extremely important, and dominates all
other for higher doping concentrations
Matthiessen rule for total mobility calculation:
1


i
1
i
Slide # 5