Put a few parts per million of phosphorus into a crystal of silicon and it conducts; put boron beside it and current flows one way only; lay a gate over a thin oxide and a field switches it on and off a billion times a second. Every chip, LED, solar cell and power converter rests on electrons and holes in a crystal whose electrons may have some energies and not others. Run on the page: the crystal and its bands; carriers, doping and the Fermi level; drift, diffusion and recombination; the pn junction, contacts and the bipolar transistor; the MOS capacitor, the MOSFET and what broke when it shrank; LEDs, lasers, photodiodes and solar cells; power switches, heat and the ageing of a chip. Bend a band diagram, grow a depletion region, shrink a transistor and light a cell — every curve computed by the page.
Every band diagram, curve and number on these pages is computed by the page or cited with its source; your progress stays in this browser. Nothing here asks you to open equipment or touch anything connected to the mains, and nothing here is a design: real devices are designed and characterised with measured data for the process in hand. The course names no product, chip or company outside its history. Not affiliated with or endorsed by any organisation, manufacturer, foundry, publisher or author mentioned here.