# [SCI] Semiconductor Physics

**Semiconductor Physics** is the quantum mechanical understanding of materials with electrical conductivities intermediate between metals and insulators, which can be precisely controlled by doping, electric fields, and temperature.

## Overview

Semiconductors have a band gap — a range of energies forbidden to electrons. At room temperature, thermal excitation promotes electrons across the gap, making conduction possible. Doping (adding impurity atoms with extra or missing electrons) creates n-type or p-type semiconductors. The p-n junction (Shockley, 1949) rectifies current; the bipolar transistor (Bardeen, Brattain, Shockley, 1947) amplifies it.

Silicon's native oxide (SiO₂) allows the MOSFET (1959), the basis of all modern microchips. Moore's Law — transistor density doubling every ~18 months — held from 1965 to ~2016, driving the digital revolution.

## Key Figures & Recognition

- **William Shockley** (1910–1989), **John Bardeen** (1908–1991), **Walter Brattain** (1902–1987): Transistor. **Nobel Prize 1956**.
- **Nick Holonyak Jr.** (1928–2022): LED (visible light), 1962.
- **Zhores Alferov** (1930–2019) & **Herbert Kroemer** (1928–): Semiconductor heterostructures. **Nobel Prize 2000**.

## Seminal Papers

- Bardeen, J. & Brattain, W. "The Transistor, A Semi-Conductor Triode." *Phys. Rev.* 74 (1948).
- [Shockley, W. "A Unipolar 'Field-Effect' Transistor." *Proc. IRE* 40 (1952)](https://doi.org/10.1109/JRPROC.1952.273964)

## What This Enables

- **[TECH] Transistor** — The p-n junction and field-effect are direct applications of semiconductor band theory to active device physics.
- **[TECH] Solar Cells (Photovoltaics)** — The photovoltaic effect — photons generating electron-hole pairs inacross a semiconductor junction — requires semiconductor physics.
- **[TECH] Semiconductor Lasers & LEDs** — Stimulated emission in quantum-well heterostructures requires understanding of semiconductor band alignment and confinement.
- **[TECH] Electric Vehicles (EVs)** — Power electronics (SiC/GaN inverters, DC-DC converters, BMS) usebattery management ICs) are semiconductor switches (IGBTs,devices.
- **[TECH] Electric Motors & Power Electronics** — IGBT and SiC MOSFETs)MOSFET power switches in variable-frequency drives are semiconductor devices enabling precise motor control.
- **[TECH] Battery Technology** — Solid-state electrolytes, silicon anodes, and battery management system ICs are semiconductor-based battery advances.

# Parents

* [SCI] Theory of Metals
* [TECH] Chemical Industry
* [SCI] Quantum Mechanics
* [SCI] Theory of Metals