Speaker Introduction:
The Electrical Engineering Distinguished Lecture Series welcomes Professor Carver Mead, an extraordinary researcher whose work has impacted academia, industry, and daily life. Mead’s contributions include electron tunneling, semiconductor interface energies, the first working MESFET, VLSI technology scaling, structured VLSI design, physics of computation, neuromorphic VLSI systems, and collective electrodynamics. He pioneered the silicon foundry concept and the fabless semiconductor business model. Mead has received numerous honors and awards, is a member of prestigious academies, and holds various fellowships. He has been a Caltech faculty member since 1958 and is currently the Gordon and Betty Moore Professor of Engineering and Applied Science Emeritus.

Carver Mead’s Opening Remarks:
Mead expresses his delight in being among friends, both old and young. He notes that electricity in ancient times was characterized by sparks, which were entertaining and allowed for magical effects but lacked quantitative applications. Benjamin Franklin made significant qualitative contributions to the understanding of electricity 130 years before Mead’s story begins. Mead’s focus is on controlled electrical current, which originated with Volta’s invention of the voltaic cell. Volta’s discovery enabled the generation of voltage and paved the way for the transition from sparks to controlled electricity.

Wheatstone’s Influence on Faraday’s Work:
Faraday’s use of Wheatstone’s null principle enabled precise measurements of resistance without absolute calibration of the galvanometer. This setup allowed Faraday to compare the resistance of different materials, such as copper and iron wires, and observe the relationship between resistance and temperature.

Discovery of Semiconductors:
Faraday’s study of silver sulfide revealed its unique properties, including its high resistance compared to metals. He observed that heating silver sulfide decreased its resistance, opposite to the behavior of metals. This led to the identification of silver sulfide as a semiconductor, a new class of materials with intriguing properties.

Braun’s Contribution to Semiconductor Research:
Braun’s investigations into the resistance of various minerals led to the discovery of asymmetric conduction, where current flow was easier in one direction than the other. This discovery marked the beginning of solid-state electronic devices and paved the way for further advancements in the field.

Hall Effect and the Movement of Charge Carriers:
Hall’s exploration of the magnetic field’s influence on current-carrying wires led to the observation of the Hall effect. This effect revealed that the force exerted on the current-carrying wire is perpendicular to both the current and magnetic field, indicating the sideways movement of charge carriers. Hall’s experiment provided evidence for the existence of mobile charges within conductors and the concept of electron drift.

Galvani’s Experiment:
Galvani observed that when two different metals are connected to the leg of a frog, it causes the frog’s leg to twitch. He theorized that “animal electricity” was responsible for this phenomenon.

Volta’s Pile:
Volta constructed a stack of alternating discs of copper and zinc separated by brine-soaked cloth. This “voltaic pile” produced a continuous electric current, becoming the first battery.

Measuring Current Direction:
Scientists realized that the direction of current flow depends on the charge of the carriers. Positive charges move in one direction, while negative charges move in the opposite direction.

Radio Communication:
Hertz demonstrated that radio waves can be transmitted and received over a distance. Marconi developed the first practical radio communication system, enabling communication between ships and the shore.

Early Radio Receivers:
Early radio receivers were crude and required a lot of radio energy to operate. The human ear was found to be more sensitive than the tape-marking devices initially used in receivers.

Rectification:
Radio waves are oscillating signals at frequencies too high for humans to hear directly. Rectifying the signal, by only considering one half of the waveform, allowed for the conversion of radio waves into audible sounds.

Semiconductors in Radio Receivers:
Semiconductors were first used in radio receivers as rectifiers. This application marked the beginning of the widespread use of semiconductors in electronics.

Early Detectors:
Crystal rectifiers were used as early radio detectors, but they were unreliable and required constant adjustment. In 1906, Picard discovered that a sharp-pointed metal contact to a polycrystalline silicon crystal produced a stable detector.

The First Real Market for Semiconductors:
The U.S. Navy adopted semiconductor detectors during World War I due to their reliability and stability, making semiconductors valuable for military applications.

Bitecker’s Exploration of Semiconductor Physics:
Bittecker sought to understand the variations in conductivity among different semiconductor samples and impurities. He hypothesized that controlled compositions of semiconductors could provide insights into their properties.

Experimental Techniques and Materials:
Bittecker experimented with various materials, including copper sulfide and copper iodide. He developed innovative sample preparation techniques to study their properties precisely.

Copper Iodide: A Remarkable Discovery:
Bittecker found that the conductivity of copper iodide films increased with the concentration of iodine in the treatment solution. This discovery marked the first time scientists could control the conductivity of a semiconductor through chemical treatment.

The Significance of Controlled Conductivity:
Bittecker’s work laid the foundation for controlling the density of charge carriers in semiconductors through controlled chemical treatments. This breakthrough underlies the development of every modern semiconductor device.

Radio’s Development and Prohibition During World War I:
After World War I, amateur radio enthusiasts were eager to utilize the vacuum tube’s advancements in radio transmission. Irving Langmuir at General Electric played a crucial role in developing the modern high-power transmitting tube.

Transmitters and Power:
High-power transmitting tubes enabled broader radio coverage and accessibility. The GE Kinetron was an early commercial transmitting tube capable of rectifying voltages up to 100,000 volts.

Broadcast Radio’s Rise:
Vacuum tubes made broadcast radio possible by providing enough power to reach a substantial audience. News, entertainment, and music were among the initial content offered on broadcast radio.

Crystal Sets:
Crystal sets, utilizing semiconductor detectors, were affordable receivers for the general public. Tube-based receivers were available but bulky, heavy, and required multiple batteries for operation.

Convenience and Affordability:
In the late 1920s, manufacturers introduced radios that could be plugged into the wall, making them more convenient and accessible for ordinary families. Crystal sets remained popular in the 1920s due to their affordability.

The Rise of Portable Radios:
Vacuum tubes enabled the development of portable radios, although they still required an antenna for operation. Smaller antennas made radios more portable and allowed people to carry them around, fostering a sense of enjoyment and community.

The Pioneering Work of Lilianfeld:
Lilianfeld was a member of a research group exploring the nascent quantum theory. He held the unconventional view that electrons were waves rather than solid particles. His experimental work challenged the prevailing theories of the time.

The Significance of Quantum Theory in Understanding the World:
Quantum theory, spearheaded by De Broglie, Schrodinger, and Heisenberg, revolutionized the understanding of the physical world. It provided a framework for calculating energy levels in atoms, particularly the hydrogen atom.

Lilienfeld’s Observation of the Transition from Semiconductor Crystal Sets to Radios:
Lilianfeld witnessed the transition from semiconductor crystal sets to radios. Semiconductor crystal sets required delicate adjustments using a “cat’s whisker detector.”

Early Radio Amplification and Vacuum Tubes:
Vacuum tubes, introduced in the early 20th century, enabled amplification of radio signals, leading to improved performance of radios. In 1913, Irving Langmuir developed a reliable and mass-producible vacuum tube, revolutionizing radio technology.

Lilienfeld’s Invention: The MESFET:
Julius Edgar Lilienfeld, inspired by the progress with vacuum tubes, envisioned amplifying signals using a semiconductor device. He proposed a structure consisting of a thin layer of gold between two glass slides, with a semiconductor material on one side. This device, which we now call the MESFET (Metal-Semiconductor Field-Effect Transistor), could modulate the current flow in the semiconductor by applying a voltage to the gold layer. Lilienfeld worked on this concept for two years but faced challenges in making it functional.

The MOSFET: An Improved Design:
Lilienfeld modified his design by replacing the gold layer with an insulator, creating a metal-insulator-semiconductor structure. This new device, known as the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), exhibited better performance and became the foundation of modern electronics. The MOSFET’s ability to control current flow with an electric field made it ideal for various applications.

Impact and Significance:
Lilienfeld’s inventions, the MESFET and MOSFET, revolutionized electronics and paved the way for the development of modern technologies. The MOSFET, in particular, became the dominant device in integrated circuits and played a crucial role in the miniaturization of electronic components. Today, MOSFETs are ubiquitous in electronic devices, including cell phones, computers, and various digital systems.

Theoretical Understanding of Solids:
While Lilienfeld focused on practical applications, his colleagues explored the theoretical foundations of solid-state physics. They investigated why metals conduct electricity, why insulators do not, and why certain materials exhibit intermediate behavior. This theoretical work laid the groundwork for understanding the electronic properties of materials and paved the way for future advancements in semiconductor physics.

Electron Energy in a Crystal:
When an electron propagates in a crystal, its energy is influenced by the positive charges in the crystal, leading to the creation of gaps in the energy spectrum.

Negative Mass Electrons:
The bottom of the energy curve corresponds to electrons with positive mass, while the top of the curve corresponds to electrons with negative mass, meaning they accelerate in the opposite direction when pushed.

Holes as Current Carriers:
The concept of holes as current carriers was introduced, and it was explained that about half of the devices in a cell phone work with holes as current carriers, while the other half work with ordinary electrons.

World War II and the Rad Lab:
The start of World War II prompted the establishment of the Rad Lab at MIT, which focused on research related to electronics and antennas.

In-House Manufacturing and Collaboration:
The Rad Lab had a glass blowing shop to produce vacuum tubes and semiconductor device packages and collaborated with industrial firms and materials labs to improve materials.

The Need for Semiconductor Detectors:
Vacuum tubes were not reliable at the high frequencies needed for radar. The only reliable point contact detector was silicon. Silicon detectors were small enough to be used in aircraft radar sets.

The Design of the Semiconductor Detectors:
The detectors were based on Braun’s and Picard’s designs. They consisted of a small piece of silicon and a catch whisker. The devices were reliable and could be mass-produced.

The Use of Semiconductor Detectors in Radar:
The detectors were used in radar sets flown on aircraft during World War II. They were essential for the development of radar technology.

The Materials Used in Semiconductor Detectors:
Silicon and germanium were the two main materials used in semiconductor detectors. Silicon was found to be the most reliable material.

The Impact of Semiconductor Detectors:
The development of semiconductor detectors was a major breakthrough in radar technology. It led to the development of smaller, more reliable radar sets that could be used in a variety of applications.

Schottky’s Theory:
German scientist Schottky published a paper in 1942 during WWII, proposing a theory for metal semiconductor contacts. He used selenium as a p-type semiconductor and explained the relationship between the energy of electrons in the metal and the positive charges in the semiconductor.

Positive Voltage and Barrier:
With a positive voltage on the metal, there’s an energy barrier that limits current flow. This positive voltage requires a negative charge on the semiconductor to absorb the electric field lines.

Negative Charge Accumulation:
Pushing positive charges back in the semiconductor leaves behind atoms with a net negative charge. The region with the electric field expands as the positive voltage on the metal increases.

Capacitance Measurement:
Schottky measured the capacitance of the metal semiconductor contact, which followed the expected relationship of capacitance being inversely proportional to the voltage squared.

Key Theoretical Understanding:
Schottky’s theory provided the first theoretical understanding of metal semiconductor contacts. It became a crucial concept for research labs working on point contact devices during WWII.

Discovery of Point Contact Transistor:
At Bell Laboratories, the search for a semiconductor device that could amplify led to the discovery of the point contact transistor. Brattain, under Bardeen’s guidance, experimented with two-point contacts on a reverse-biased junction, observing that current in one contact affected the current in the other. This effect resulted from the movement of opposite-sign carriers (holes) over the energy barrier, rather than the expected flow of electrons. The first understood active device was created by connecting the two contacts with a transformer, resulting in oscillation.

Shockley’s Theory and the Junction Transistor:
Shockley proposed a model for the point contact transistor, suggesting that it consisted of two n-type semiconductor regions separated by a thin p-type region. This model led to the development of the junction transistor, which had a more reliable and controllable structure compared to the point contact transistor. The junction transistor could be fabricated by introducing a p-type region between two n-type regions in a semiconductor material.

Manufacturing of Early Transistors:
Early transistors were often occluded and difficult to manufacture reliably. Penkov invented a simple and reliable method for making transistors by dissolving germanium in molten indium and then cooling the mixture, resulting in the formation of a p-n-p transistor structure. This method allowed for precise control of the doping levels and resulted in transistors that could operate up to about a megahertz.

Raytheon’s CK722 Transistor:
Raytheon introduced the CK722 transistor, which was affordable and widely used in laboratory experiments. Despite its limited frequency range, the CK722 transistor played a significant role in the early development of electronic circuits.

Philco’s Innovative Transistor Manufacturing Process:
Philco developed a remarkable technique for transistor production, involving a germanium flake with spouts on both sides. Electrolyte was squirted onto the germanium, etching it away in one direction and depositing indium in the opposite direction. This automated process enabled the precise creation of PNP transistors.

Infrared Light as a Thickness Gauge:
Germanium’s ability to absorb infrared light exponentially with thickness was utilized to determine the optimal stopping point during the manufacturing process. Shining infrared light through the electrolyte and measuring the transmitted light allowed for accurate thickness control.

Economic Feasibility and Improved Performance:
Philco’s technique resulted in economically viable transistors with a reliably thin base region, leading to better transistor performance. These transistors could oscillate at significantly higher frequencies (70 megahertz), enabling their use in radio applications.

A Glimpse into the Automated Factory:
Carver Mead visited Philco’s automated transistor factory in Bluebell, Pennsylvania, witnessing the impressive and efficient manufacturing process firsthand. The factory utilized precise indexing, wire attachment, and packaging, resulting in a continuous production of transistors.

Origins of Silicon Transistors:
Bell Labs researchers developed a method for creating junctions in silicon by diffusing impurities. This process allowed for precise control of transistor dimensions and doping concentrations, resulting in faster transistors compared to germanium transistors. The ability to fabricate multiple transistors on a single silicon wafer made it possible to produce economical transistors.

The Birth of Integrated Circuits:
Bill Shockley’s research team at Caltech explored four-layer devices for power switching applications. Fairchild Semiconductor, founded by Gordon Moore, John Herney, and Bob Noyce, focused on developing silicon transistors. Texas Instruments introduced a high-frequency silicon transistor, inspiring Jack Kilby’s idea of connecting transistors and resistors on a single silicon wafer.

Challenges and Breakthroughs:
Jack Kilby faced the challenge of interconnecting transistors on a wafer, resulting in a circuit with flying leads that required external wiring. Jean Herney’s planar process allowed for selective diffusion of impurities and precise control of oxide layers, enabling true integrated circuits. Bob Noyce recognized the potential of Herney’s process and filed a patent for the integrated circuit.

The Herney-Noyce Insight:
John Herney’s patent disclosure, signed by Bob Noyce, outlined the concept of connecting any part of a transistor using a wire, leading to the development of the modern integrated circuit. Jack Kilby’s vision, combined with Herney and Noyce’s insights, paved the way for the miniaturization and integration of electronic circuits.

The MOS Transistor:
Carver Mead discusses the development of the MOS (metal-oxide-semiconductor) transistor, which was made possible by the reliable fabrication of silicon-silicon oxide interfaces. The MOS transistor is a simple device with a metal gate, an oxide layer, and a silicon semiconductor, making it the first commercially viable field effect device. It enables the representation of a 1 or 0 using different voltages, allowing for logic operations.

CMOS:
Frank Wanless at Fairchild Semiconductor developed a complementary MOS (CMOS) circuit design that uses both P-channel and N-channel transistors to pull the output up and down. This design reduces current flow by ensuring that one transistor is always off, enabling logic operations with minimal power consumption.

Dynamic RAM:
Bob Dennard at IBM invented dynamic RAM (random-access memory), which temporarily stores charge on a transistor gate and refreshes it during read operations. This eliminates the need for constant pull-up and pull-down transistors, reducing transistor count and power consumption.

MESFET:
Lilienfeld’s initial invention, the MESFET (metal-semiconductor field-effect transistor), was finally fabricated at Caltech, providing Mead with personal satisfaction in realizing Lilienfeld’s vision.

Moore’s Law:
Gordon Moore’s observation that the number of transistors on a chip doubles every year led to the relentless pursuit of smaller, faster, and more power-efficient devices. This focus shifted the emphasis from developing new electron devices to refining existing ones, resulting in Moore’s Law’s sustained validity.

The Role of Vacuum Tubes:
Mead highlights the crucial role of vacuum tubes in creating a market for semiconductor devices. Without the widespread adoption of radio, which relied on vacuum tubes, the demand for semiconductors would have been significantly lower, hindering their development.

The Future of Computing:
Mead reflects on the uncertainty of the next generation of computing technologies. He emphasizes the importance of continuous refinement and improvement, as exemplified by Steve’s work on field programmable devices. Mead suggests that neural networks, which have recently become viable due to technological advancements, may play a significant role in future computing.

Predictions and Surprises in Technological Advancements:
* Carver Mead reflects on his earlier predictions and the unexpected success of Steve’s research, which was initially dismissed but is now gaining attention.

Vacuum Tubes Revisited:
* Mead highlights the potential resurgence of vacuum tubes, given their promising performance at the nanoscale.
* Ken Shoulders’s experiments in the 1960s demonstrated the feasibility of micron-sized vacuum tubes.
* Axel Schur’s current work on nanoscale vacuum tubes shows promise due to favorable scaling properties and electron flow characteristics.

Challenges in Passing on Technological Knowledge:
* Mead expresses concern about the lack of knowledge transfer from experienced inventors to the younger generation.
* The educational system has not adequately preserved the lore of device invention, leading to a shortage of skilled innovators.

Hope for the Next Generation:
* Mead encourages the audience to support and root for the next generation of innovators who will shape the future of technology.

Question and Answer Session:
* SPEAKER_04 asks about the biggest mistake people made in their approach to technology development.
* Mead responds by expressing his disappointment that Julius Lilienfeld did not discover selenium, which hindered the early progress of field-effect transistors.

The Tragedy of Early Transistor Pioneers:
Despite his brilliance, the lack of success with his chosen materials prevented Oleg Losev from witnessing the fruition of his work. If he had opted for selenium instead of copper sulfide, his devices would have functioned, accelerating the evolution of electronics.

Self-Assembling Devices:
Mead believes self-assembling devices might be the next frontier, but he cautions that it may take time for practical applications. Fault tolerance will be crucial for commercial viability, and neural systems offer potential solutions.

Fostering Creativity:
Caltech’s strength lies in its exploration of unorthodox directions, increasing the chances of groundbreaking discoveries. Avoiding groupthink and encouraging diversity in research approaches is essential for innovation.

AT&T’s Slow Adoption of Transistors:
The Bell System’s focus on dominance in applied science and the consent decree limiting their commercialization of inventions hindered the adoption of transistors. Despite this, Bell remained at the forefront of MOS transistor research.

Politics and Technology:
The increasing political influence on technology necessitates consideration of how external factors will impact technological progress.

Groupthink in Technology:
Carver Mead observes that technology today is dominated by groupthink, where innovation is often stifled by the tendency to focus on incremental improvements rather than truly disruptive ideas.

Breaking Through Groupthink:
Mead believes that Caltech is well-positioned to break through this groupthink due to its culture of encouraging unconventional thinking.

The Challenge of Innovation:
Mead emphasizes the difficulty of introducing new ideas that challenge established norms, as they often face resistance from those who are comfortable with the status quo.

The Case of Lilienfeld’s Invention:
Mead cites an example from the history of transistors, where an analysis of Lilienfeld’s invention was flawed due to the prevailing mindset that all transistors were minority carrier devices.

The Strength of Groupthink:
Mead stresses the strength of groupthink, highlighting the need for extraordinary effort and perseverance to overcome it and drive meaningful innovation.