In silicon, electrons have to emit a photon and a sound vibration (a phonon) at the same time to reach the valence band. Instead, the electron typically finds a way to lose the energy without ...

One way to force silicon to emit light is to illuminate it with a separate light source: this excites electrons from the valence band into the conduction band, from where they fall back down to the ...

They consist of two layers of silicon - on one side there’s an excess of valence electrons, and in the other a deficit. This is achieved by doping - contaminating each layer by a different element.

By "decorating" the silicon surface, the researchers said, ... "In direct bandgap semiconductor materials, electrons transition from the valence band to the conduction band.