cw 25 hall k.pdf

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Instytut Fizyki Dowiadczalnej Wydzia Matematyki, Fizyki i Informatyki

UNIWERSYTET GDASKI

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Instytut Fizyki Dowiadczalnej 1.

Experiment 25 : Hall effect in p-type and n-type doped germanium

I. Background theory.

1. Fundamentals of band theory.

2. Classification of solids using band theory.

3. Intrinsic and doped semiconductors.

4. Electrical and thermal conductivity of semiconductors.

5. The Hall effect and its applications.

6. The Hall constant, conductivity of materials, concentration and mobility of charge carriers.

7. Construction and use of Hall probes.

II. Experimental tasks.

1. Refer to the setup shown in Picture 1 and the operating instructions in the Appendix .Place the measuring module (1) indicated by the laboratory supervisor between the poles ofthe electromagnet (3).

2. Before taking measurements, zero the teslameter using the knob on the right-hand side ofthe front panel (6) after removing the teslameter probe (5) from the electromagnet (3)(Picture 1 ).

Picture 1. Experimental setup for studying the Hall effect:1 measurement module with Hall effect sensor; 2 electromagnet and module power supply; 3 electromagnet;

4 universal multimeter; 5 teslameter probe; 6 teslameter.

3. Insert the magnetic field probe (5) into the measuring module (1) with the Hall effect sensor.

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4. Compensate for the Hall voltage UH using the knob on the right-hand side of the measuringmodule (1) with a current strength I = 0 A and magnetic field strength B=0 T. This step shouldbe repeated before the next series of measurements.

5. Take measurements of the Hall voltage UH as a function of the control current I.Plot graphs of your results UH = f(I) and U = f(I). Include all appropriate measurement uncertainties.

6. Take measurements of the voltage U p across the probe as a function of magnetic field

strength . Plot a graph of the relative change of electrical resistance (R(B)-R0 )/R 0 = f(B), where R0 probe resistivity with no magnetic field.Calculate the conductivity of the sample with the formula = l/(R 0 A), where l =20 mm,

A=10 mm 2.7. Measure the Hall voltage UH as a function of magnetic field strength B.

Plot a graph of UH = f(B).Using linear regression to determine the value of the Hall constant R H, taking the samplethickness to be d = 1 mm.Calculate the concentration n and mobility of the charge carriers.

8. Measure the Hall voltage UH as a function of temperature UH = f(T). Plot a graph of UH = f(T).Indicate measurement uncertainties in your plot. Interpret your results.

III. Apparatus.

1. Three modules with Hall effect sensors.2. Module and electromagnet power supply.3. Electromagnet.4. Universal multimeter.5. Teslameter probe.6. Teslameter.

IV. Literature.

1. Ch. Kittel Introduction to Solid State Physics , John Wiley & Sons, 2004.2. W. Ashcroft Solid State Physics , Saunders College, Philadelphia 1976.3. Solid State Physics. Pt. B, Electrical, Magnetic, and Optical Properties ed. by K. Lark-Horovitz

and Vivian A. Johnson, London: Academic Press, New York 1959.4. J. Orear Physics, Vol.2., Macmillan Publishing Co., Inc., 1979.

5. PHYWE Laboratory Experiments Physics, 2010, www.phywe.com .6. A.P. Arya Fundamentals of Atomic Physics , Allyn & Bacon , Inc. Boston 1971.

The magnetic field probe (5) is very delicate and should be gently inserted into themeasuring unit (1) being very careful not to damage it!
http://www.phywe.com/http://www.phywe.com/http://www.phywe.com/http://www.phywe.com/

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AppendixHints for making measurements

Appx. . II. 5.

Measure the Hall voltage using the digital multimeter (4) connected to the measurement module(1) as a function of sample control current in the range -30 mA to 30 mA in steps of 5 mA.To adjust the control current I, use the dial on the left-hand side of the measuring module (1).The current can be read off the display on the measuring module.

Appx. . II. 6.

With constant control current I = 30 mA, take measurements of the sample voltage U p with thedigital multimeter (4) connected to the measuring module (lower output on the measuringmodule (1 in Picture 1 ) as a function of magnetic field strength B in the range 0 to 300 mT in stepsof 20 mT.The magnetic field strength B is read off the teslameter display (6) and should be set by properlychoosing the voltage and current on the power supply (2).

Appx. . II. 7.

With constant control current I = 30 mA, take measurements of the Hall voltage UH with thedigital multimeter (4) connected to the measuring module (upper output on the measuringmodule (1 in Picture 1 ) as a function of magnetic field strength B in the range 0 to 300 mT in stepsof 20 mT.The magnetic field strength B, is read off the teslameter display (6) and should be set by properlychoosing the voltage and current on the power supply (2).

Appx. . II. 8.

With constant control current I = 30 mA and magnetic field strength B = 300 mT, take

measurements of the Hall voltage UH with the digital multimeter (4) connected to the measuringmodule (1) as a function of temperature.Take a temperature range starting from room temperature, i.e., about 20 oC, to 140 oC in steps of10 oC.

After enabling the heating coil, the sample will be rapidly heated. Pay specialattention not to exceed a temperature of 150 oC.

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The temperature should be read from the display located on the measuring module (1) aftersetting the measuring module to temperature mode (with the Display button).Start the measurement when you turn on the sample heating coil, which is built into the

measurement module (1), using its On/Off button on the rear of the measuring module.After reaching a temperature of 140 oC, turn off the sample heating coil.

For measurements with the heating coil, take care for at least 5 minutes whenhandling the measuring module (1).Touching the measuring module plates during this time may cause serious burns.

cw 25 hall k.pdf

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