Photonic p-n junction devices
The p-n junctions can be designed so that current through them changes either by causing electron excitation (from valence band to the conduction band) by light photons, or conversely through electron excitation by a suitable bias voltage resulting in the emission of light photons. These semiconducting devices are called photonic or opto-electronic devices. In such devices, light photons play an important role in the overall functioning of the device.
The photonic p-n junction devices can be classified as follows:
(i) Photo-detectors used for detecting light signals e.g., photodiodes and photoconducting cell.
(ii) Photovoltaic devices which convert light energy into electricity e.g., solar cells.
(iii) Devices for converting electrical energy into light e.g., light emitting diodes and diode lasers.