The invention of the transistor at Bell Labs in 1947-1948 marked a seminal milestone that birthed the era of solid-state electronics and computing as we know it. Shockley, Bardeen and Brattain‘s breakthrough built upon over a century of scientific inquiry into the curious electrical properties of semiconducting materials.
In this blog post, I‘ll trace the key waypoints along this journey – from early 19th century experimental observations to early 20th century vacuum tube devices to the game-changing Bell Labs transistor demonstration. My aim is to highlight both the incremental discoveries that constructed a foundation of semiconductor knowledge as well as the towering genius of the transistor‘s creators in sculpting this capability into a practical device.
I‘ll cover topics like:
- The pioneering scientists who uncovered rectification and photoelectric effects
- Early radio wave detectors and crystal radios using crude semiconductor points
- Julius Lilienfeld‘s trailblazing patented ideas for a solid-state amplifier
- Bell Labs‘ methodical testing of various substances leading to germanium and silicon
- The Eureka moment when Bardeen and Brattain first observed amplification from their circuit
So join me on an enriching tour across the landscape of inorganic chemistry, quantum physics and electrical engineering wizardry! Hopefully you‘ll come to appreciate how society-reshaping innovations require marshaling many years of collaborative human ingenuity.
Sparking Curiosity: Early Research into Exotic Semiconductor Properties
Our chronicle opens in 1833 with the renowned English scientist Michael Faraday noting an odd effect while experimenting with silver sulfide. He observed that this compound‘s electrical resistance decreased when heated, contrasting with the resistivity rise typically seen in metals. Faraday recorded one of the earliest observations of what later became recognized as a semiconductor‘s distinctive characteristics.
The story continues in 1874 Germany, where Heidelberg University physicist Karl Ferdinand Braun discovered another perplexing semiconductor trait – asymmetric conductivity. Braun explored mineral galena crystals and metal point contacts as detectors for wireless telegraphs. He stumbled upon electric currents flowing only in one direction at a junction between the galena and a wire point.
| Year | Discovery | Scientist | Significance |
|---|---|---|---|
| 1833 | Decreasing electrical resistance when heated in silver sulfide | Michael Faraday | Semiconductor effect |
| 1874 | Asymmetric conductivity through lead sulfide crystals | Karl Ferdinand Braun | First semiconductor diode |
These bizarre yet intriguing effects sparking early interest ultimately trace back to the quantum mechanical properties governing crystalline structures inside semiconductors. Their unique electron band diagrams enable exotic electronic transport untouched by prevalent conductors and insulators of the 1800s.
While the underlying science awaited 20th century formulation, early experimental anomalies already hinted at novel functionalities hampered by contemporary materials. These seeds of curiosity flowered into a rich lineage of global tinkering and patenting activity that unlocked the latent technological potential of semiconductors.
Of Crystal Radios and Primitive Rectifiers
The decades between 1895-1925 saw a Cambrian explosion of inventor creativity yielding primitive electronic devices harnessing newly-discovered semiconductor capabilities.
Greenleaf Whitter Pickard, an AT&T engineer, filed an influential 1906 patent for a revolutionary radio receiver technology. This so-called silicon "cat‘s whisker" detector extracted AM radio signals by exploiting semiconductor point contact rectification much like Braun did earlier. Running a fine metal wire against silicon crystals produced asymmetric conductivity allowing only one AC phase to pass.
An early 20th century crystal radio using a semiconductor cat‘s whisker detector. [1]
This simple yet effective rectification astonished contemporary electrical engineers and quickly achieved widespread adoption. Early radio hobbyists eagerly assembled crystal sets to catch broadcasts using just antenna wires and headphone listening.
Cat‘s whisker detectors largely focused on receiving rather than amplifying signals. But other inter-war period tinkerers like Julius Edgar Lilienfeld pondered even loftier ambitions through semiconductor devices.
Premonitions of Solid-State: Patents Ahead of Their Time
Julius Lilienfeld emigrated from Austria-Hungary to North America in the 1920s harboring deep fascination for physics research into electronic transports and copper oxide rectifiers. His subsequent filings describing semiconductor devices conceptually foretold modern transistors decades prior to their physical debut!
A 1925 Canadian patent application outlined a device with two input connections allowing a third electrode to variably control output current.
"Method and apparatus for controlling electric current by variations in the electron conducting qualities of semi-conductors under the action of electron bombarding ions." [2]
His 1926 US patent elaborated on a thin film field effect amplifier astonishingly akin to contemporary MOSFETs! Lilienfeld unambiguously pursued solid-state configurations for precisely directing current flows through semiconductor materials using electric fields. The scientific theory supporting such ideas still awaited maturation.
Nonetheless, Lilienfeld‘s patents embody the remarkable insight that semiconductors could assume control, signaling and amplification roles then dominated by bulky, power-hungry vacuum tubes. He envisaged a future when delicate electrons dancing across silicon substrates would replace mechanical relays and pneumatic actuators.
While these patents generated meager contemporary interest, they did help convince Bell Labs to ultimately abandon vacuum tubes and commit manpower into exploring solid-state materials. And they provided sufficient legal argument about prior art to initially threaten Shockley‘s transistor patent claims before later revisions secured acceptance.
Methodical Advance: Bell Labs‘ Wartime Materials Science Exploration
We now fast-forward several decades to the iconic American Telephone & Telegraph Bell Laboratories which marshaled tremendous scientific talent throughout the 1930s-1940s toward creating ever more capable communications systems. Their best minds scrutinized alternatives to the venerable yet power-hungry Audion vacuum tubeworkhorse rapidly hitting practical limits.
Wartime urgency toward radar development spurred materials research into suitability for high frequency operation. Bell recruited solid state physics rockstars like William Shockley to systematically evaluate various substances, including prototypical compounds like silicon and germanium.
The table below summarizes Bell Labs‘ extensive empirical testing cataloging electrical parameters that could enable next-gen devices [3]. While much data proved disappointing, a few semiconductors showed enticing conductivity modulation potential upon introduction of specific impurities.
| Year | Substance | Conductivity (ohm-cm)-1 | Comments |
|---|---|---|---|
| 1940 | Germanium | 10^-2 to 10^+2 | Reacts to impurities |
| 1941 | Silicon | 10^-5 | Poor room temperature conductivity |
| 1941 | Selenium | 10^-12 | Changes resistance upon light |
| 1942 | Silicon Carbide | 10^-10 | Inadequate purity |
Their exhaustive experiments incrementally constructed world-class semiconductor fabrication expertise. This platform crucially empowered Bardeen and Brattain‘s fateful 1948 discovery of "transistor action" amplification effects at a germanium point contact – the Eureka moment catalyzing silicon‘s future domination.
Shockley immediately grasped transistors‘ epochal significance and marshaled resources into productizing Bell‘s startling lab prototype over ensuing years. Concerted advancement efforts birthed the inaugural germanium junction transistor commercial release in 1951.
The Triumph of Science and Open-ended Tinkering
Our remarkable journey through early semiconductor history highlights how scientific revolutions equally rely on meticulous research methodologies as on relentless open-ended tinkering. Both aspects cooperated in birthing the transistor, perhaps the most generative offshoot ofquantum discoveries in the 20th century.
Faraday and Braun‘s explorations revealing exotic physical effects; Pickard and Lilienfeld‘s inventive prototypes harnessing functionality; and Bell Labs‘ industrial-scale experimentation combined to transform raw semiconductor minerals into the active substrate for society‘s computing infrastructure.
So next time you gaze at integrated circuit cards with billions of microscopic transistors, or read about advancing nanometer node processes, take a moment to appreciate the fruits of this cumulative transnational enterprise stretching over a century! Our modern digital age owes its existence to numerous scientists and engineers who collectively elevated an intriguing material into the building block of modern electronics.
- By Tvanerp – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7966136
- Julius Edgar Lilienfield Patents: https://nationalmaglab.org/about/history/inventors-facilities/lilienfeld
- Bell Labs Semiconductor Research: https://www.bell-labs.com/our-research/memory-semiconductor/
