1. The first transistor & Van der Pauw method
Tom Mauersberger
Dresden,

2. The first transistor & van der Pauw method
Content
Introduction – In a time before the transistor The first transistor The road to the first transistor The magic day – 16th december 1947 How did it work? Van der Pauw method The idea behind Measurement procedure Summary
The first transistor & van der Pauw method

3. Introduction: In a time before the transistor
[Sharp, Journal of AIEE,Vol.41,No.1,1922]
19th century: many people investigated vaccum tubes  one of them: Thomas Edison
Investigation on how cathode current ( temperature) changed anode current: Edison-Effect (Thermionic Emission) 1883
1904 John Ambrose Fleming discovered rectifying effect of these devices : first thermionic diode
1907 Lee De Forest built first device, that was later to become the triode and the first electronic amplifier (recognized later)
The first transistor & van der Pauw method

4. The vacuum thermionic triode[ [ [
The first transistor & van der Pauw method

5. The first transistor & van der Pauw method
Content
Introduction – In a time before the transistor
The first transistor
The road to the first transistor
The magic day – 16th december 1947
How did it work?
Van der Pauw method
The idea behind
Measurement procedure
Summary
The first transistor & van der Pauw method

6. The road to the first transistor – Field effect
In 1945 Bell Laboratories started reasearch progam on semiconductors with the goal to build a solid state semiconductor amplifier
Started with field effect experiments because Shockley only achieved negative results in the past
Bardeen suggested bound surface states shielding the field effect
This led the research program into investigating surface properties
[J.Bardeen, Nobel Lecture, 1956]
The first transistor & van der Pauw method

7. The first idea of a solid state amplifier
Point contact surrounded by, but insulated from, a drop of electrolyte
Positive bias at point contact  small reverse current
Strong field applied at SC surface by control electrode in the electrolyte
change of current was observed - negative bias at electrolyte decreased current
Increasing aim to build field effect transistor
[J.Bardeen, Nobel Lecture, 1956]
The first transistor & van der Pauw method

8. First indicator of transistor effect
[J.Bardeen, Nobel Lecture, 1956]
Change from Si to Ge
Field effect by evaporated gold electrodes seperated by thin oxide from the SC
“Although none (of the contacts) made the desired high resistance contact to the block, we decided to see what effects would be obtained” – J.Bardeen
Small reverse current at tungsten point contact
positive bias at gold spot increased rather than decreased the reverse current
Suggestion of holes flowing from gold spot to tungsten point contact
P - type [
The first transistor & van der Pauw method

9. The magic day – 16th december 1947[
[Bardeen, Brattain, Phys.Rev. 74,1948]
Polysterene wedge with gold foil
Slit in the middle  two point contacts with distance of about 50 µm
high reverse bias at collector, forward bias at emitter
Holes get injected at emitter, flow in forward bias direction and get attracted by strong reverse bias towards collector
Transistors were immediatley: x less power consuming than tubes - 100x smaller than tubes - 100x faster than tubes - 10x more expensive than tubes
The first transistor & van der Pauw method

10. The first transistor & van der Pauw method
How did it work?
Emitter P
Base N
Collector P [
The first transistor & van der Pauw method

11. The first transistor & van der Pauw method
content
Introduction – In a time before the transistor
The first transistor
The road to the first transistor
The magic day – 16th december 1947
How did it work?
Van der Pauw method
The idea behind
Measurement procedure
Summary
The first transistor & van der Pauw method

12. Van der Pauw method - Idea
First propounded by Leo J. van der Pauw in 1958 [van der Pauw, Philips Research Reports, 13, 1958]
Idea: measure specific resistivity and Hall-coefficient of arbitrarily shaped sample
From the measurements we get: - specific resistivity
- doping type
- majority carrier density
- mobility of majority carriers
The first transistor & van der Pauw method

13. Measurement procedureV
Measurement procedure D C
Define RAB,CD=VCD/IAB , measure RAB,CD and RBC,DA
Reciprocity theorem: RAB,CD=RCD,AB V A
Complicated maths
(Conformal mapping of two-dimensional fields)
Van der Pauw equation: A B A
Conditions: - contacts at circumference - small contacts - homogenous thickness - no isolated holes
The first transistor & van der Pauw method
[van der Pauw, Philips Research Reports, 13, 1958]

14. The first transistor & van der Pauw method
Summary
Transistor seems superior in all applications but in some fields vacuum tubes are still used, e.g. spaceships
Most important discovery: flow of holes and electrons at the same time
„If Schottky in the ‘30s had looked here to see what the holes were doing, the transistor would have been invented then.“ (J.Bardeen, 1950´s)
First transistor was a pnp point contact transistor
Van der Pauw: most important semiconductor properties by only few measurements
Independent of sample geometry (only thickness is necessary)
Valid for homogenous sample with small contacts at circumference
The first transistor & van der Pauw method

15. Thanks for your attention!
Questions?
The first transistor & van der Pauw method