Energy Conduction band Filled states Band Emitted gap AEhund photon Empty states Filed Valence band states FIGURE P29.70 Energy-level diagram of an LED.
Light-emitting diodes, known by the acronym LED, produce the familiar green and red indicator lights used in a wide variety of consumer electronics. LEDs are semiconductor devices in which the electrons can exist only in certain energy levels. Much like molecules, the energy levels are packed together close enough to form what appears to be a continuous band of possible energies. Energy supplied to an LED in a circuit excites electrons from a valence band into a
Suppose the LED band gap is 2.5 eV, which corresponds to a wavelength of 500 nm. Consider the possible electron transitions as shown. 500 nm is the
A. Maximum wavelength of the LED.
B. Average wavelength of the LED.
C. Minimum wavelength of the LED.
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