A band gap is the distance between the valence band of electrons and the conduction band…
Physics20265 marksCase based
A band gap is the distance between the valence band of electrons and the conduction band. Essentially, the band gap represents the minimum energy that is required to excite an electron up to a state in the conduction band where it can participate in conduction. The lower energy level is the valence band, and thus if a gap exists between this level and the higher energy conduction band, energy must be input for electrons to become free.
An LED is made of a p-type semiconductor material (which has a higher concentration of "holes" or positive charge carriers) and an n-type semiconductor material (which has a higher concentration of electrons or negative charge carriers). This recombination process releases energy in the form of light and heat. The specific wavelength (and therefore the colour) of the emitted light depends on the energy band gap of the semiconductor material used.
I-V characteristic of LED bulb is given below.
(i)
Identify the wavelength that has: (Application)
(a) The maximum energy gap
(b) The minimum energy gap
(ii)
$E$ is the energy of the incident photon and $E_g$ is energy gap, which is produced across the depletion layer. What will happen in the following cases: (Understanding)
(a) $E > E_g$
(b) $E = E_g$
(c) $E < E_g$
Answer
No answer yet.
Semiconductor Electronics: Materials, Devices and Simple Circuits
