The first transistor & Van der Pauw method Tom Mauersberger Dresden, 01.11.2016

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 30.01.2018 The first transistor & van der Pauw method

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) 30.01.2018 http://robinsonlibrary.com] The first transistor & van der Pauw method

The vacuum thermionic triode [http://allaboutcircuits.com] [http://daenotes.com] [http://en.wikipedia.org/triode] 30.01.2018 The first transistor & van der Pauw method

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 30.01.2018 The first transistor & van der Pauw method

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] 30.01.2018 The first transistor & van der Pauw method

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] 30.01.2018 The first transistor & van der Pauw method

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 [https://en.wikipedia.org/wiki/Metal-semiconductor_junction] 30.01.2018 The first transistor & van der Pauw method

The magic day – 16th december 1947 [http://rfcafe.com] [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: - 100x less power consuming than tubes - 100x smaller than tubes - 100x faster than tubes - 10x more expensive than tubes 30.01.2018 The first transistor & van der Pauw method

The first transistor & van der Pauw method How did it work? Emitter P Base N Collector P [http://slideplayer.com/slide/9405792/] 30.01.2018 The first transistor & van der Pauw method

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 30.01.2018 The first transistor & van der Pauw method

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 30.01.2018 The first transistor & van der Pauw method

Measurement procedure V 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 30.01.2018 The first transistor & van der Pauw method [van der Pauw, Philips Research Reports, 13, 1958]

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 30.01.2018 The first transistor & van der Pauw method

Thanks for your attention! Questions? 30.01.2018 The first transistor & van der Pauw method