Slide # 1

Measurement of Hall voltage and resistivity

B

A

R

RQ )(

2ln2 23

14

12

43 QFI

V

I

Vsheet

where

Measurement of Sheet Resistivity Measurement of Hall voltage

tsheet Here, t = thickness of the sample

Resistivity

sheet

sheetsheet qqn

1

Slide #

Variation of F with Q

2

F(Q) = 1, if RA = RB

Slide # 3

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 # 4

Hall Effect sensor: Chip and Spec

ANALOG DEVICES - AD22151YRZ - IC,

HALL EFFECT SENSOR, LINEAR, 8-SOIC

Slide # 5

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

i i

11

Matthiessen rule for total mobility calculation: