Silicon valley: Scanning electron microscopy image of the laser-irradiated silicon surface (inset), which resembles a fragment of Bryce Canyon National Park in Utah, USA.

The p-type silicon is produced by adding atoms—such as boron or gallium—that have one less electron in their outer energy level than does silicon. Because boron has one less electron than is required ...

This leaves one silicon atom with a vacant location in its outer shell, called a "hole," that readily accepts an electron. Because the charge carriers are holes, p-type silicon is said to have a ...