What happens when an electron fills a hole?

When an electron fills a hole, the process is referred to as recombination. In semiconductor physics, a hole represents the absence of an electron in a semiconductor's valence band. When an electron from the conduction band transitions down to occupy this hole, it effectively neutralizes the charge imbalance created by the absence of an electron. This action reduces the number of free charge carriers available for conduction, which can alter the electrical properties of the material.

Recombination can occur through radiative or non-radiative processes, and in the case of radiative recombination, it can lead to the emission of light, which is a fundamental principle in opto-electronics used in devices such as LEDs and laser diodes. In summary, the filling of a hole by an electron constitutes recombination, which has significant implications in the behavior of semiconductors and the performance of electronic and optoelectronic devices.