From a curious discovery to the transistor
In 1833 Michael Faraday recorded that silver sulfide conducts better as it gets hotter — the opposite of metals. In 1874 the German physicist Karl Ferdinand Braun found that certain metal sulfides let current pass in only one direction; this rectification later powered the crystal detectors of early radio. Why it happened had to wait for quantum mechanics: in 1931 Alan Wilson explained semiconductors with band theory. In December 1947 John Bardeen and Walter Brattain at Bell Labs built the first transistor from germanium, William Shockley developed the junction transistor theory the next year, and all three shared the 1956 Nobel Prize in Physics. In 1958–59 Jack Kilby and Robert Noyce created the integrated circuit, and in 1959 Korean-born Dawon Kahng and Mohamed Atalla built the MOSFET, the basic device in today's chips.
Band gaps and doping
Electrons must reach the "conduction band" to carry current, and the energy gap to get there is the band gap. Metals have none, insulators have a wide one, and semiconductors have a narrow one that heat or light can push some electrons across. Adding a little phosphorus to silicon gives n-type material with spare electrons; adding boron gives p-type material with "holes". Joining the two makes a p-n junction — a diode that conducts one way — and also the solar cell (Bell Labs, 1954), the LED and the semiconductor laser. The blue LED developed in the 1990s by Shuji Nakamura and others made white LED lighting possible and won the 2014 Nobel Prize.
| Class | Conductivity | Examples |
|---|---|---|
| Conductor | Very high | Copper, silver, aluminium |
| Semiconductor | Controllable | Silicon, germanium, gallium arsenide |
| Insulator | Almost none | Glass, rubber, diamond |
Moore's law and the chip industry
In 1965 Gordon Moore predicted that the number of components on a chip would double every year (revised to every two years in 1975), and "Moore's law" became the industry's target for half a century. Today's most advanced chips hold tens of billions of transistors on a fingernail-sized die. Chips divide into memory (DRAM, NAND flash) that stores data and logic chips (CPUs, GPUs, image sensors) that compute and control. South Korea became a memory powerhouse after Samsung's 64-kilobit DRAM in 1983, and Taiwan's TSMC pioneered the foundry model of manufacturing chips for others. As features shrink to a few nanometres, extreme-ultraviolet lithography tools and rare materials have become matters of national strategy, and recovering metals from e-waste through urban mining is drawing attention.
FAQ
- Why is silicon the most common semiconductor?
- Silicon is abundant (it comes from sand), has a convenient band gap, and easily forms a high-quality oxide layer (SiO₂) on its surface, which makes MOSFETs practical.
- Is Moore's law dead?
- Transistor shrinking has slowed sharply since the 2010s. The industry now keeps improving performance through 3D stacking, advanced packaging and new materials.
Sources reviewed: 2026-10-26
References
- Braun, F. (1874). Über die Stromleitung durch Schwefelmetalle. Annalen der Physik und Chemie, 229(12), 556–563.
- Wilson, A. H. (1931). The theory of electronic semi-conductors. Proceedings of the Royal Society A, 133(822), 458–491.
- Bardeen, J., & Brattain, W. H. (1948). The transistor, a semi-conductor triode. Physical Review, 74(2), 230–231.
- Shockley, W. (1949). The theory of p-n junctions in semiconductors and p-n junction transistors. Bell System Technical Journal, 28(3), 435–489.
- Chapin, D. M., Fuller, C. S., & Pearson, G. L. (1954). A new silicon p-n junction photocell for converting solar radiation into electrical power. Journal of Applied Physics, 25(5), 676–677.
- Kilby, J. S. (1964). Miniaturized electronic circuits. U.S. Patent No. 3,138,743.
- Moore, G. E. (1965). Cramming more components onto integrated circuits. Electronics, 38(8), 114–117.
- Nakamura, S., Mukai, T., & Senoh, M. (1994). Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes. Applied Physics Letters, 64(13), 1687–1689.
- Sze, S. M., & Ng, K. K. (2007). Physics of Semiconductor Devices (3rd ed.). Hoboken, NJ: Wiley.