Chemistry Reference
In-Depth Information
6.2
How Does LED Work?
Similar to a regular diode, LED is a device made of semiconducting
material doped with impurities to create a p-n junction. Light is
emitted when an electric current is passed through the semiconductor
device. When the p-n junction in the LED is under forward biased, the
holes in the p-type material are pushed toward the junction while
the electrons in the n-type material are pushed toward the junction
(Fig. 6.1). This creates a narrower depletion region and lowers the
potential barrier. With continual forward-biased voltage, the electrical
resistance at the junction may be overcome. The electrons and holes
combined at the junction, maintaining a continuous current. Electrons
from the conduction band flow from the n-type region to combine
with the holes from the valence band from the p-type region. As the
electron and hole recombine at the p-n junction, light with an energy
hv
is emitted. Wavelength of light emitted is corresponding to the
bandgap energy of the semiconductor material [24].
=
E
g
Figure 6.1
Potential energy vs distance graph showing the movement of
holes and electrons at the p-n junction [25].
