Dear Jaya,
I assume, you refer to the lifetime of carriers in the thermal equilibrium. The following statements cannot be applied to the lifetime of excess carriers.
The lifetime of majority carriers t can be calculated, if the mobility µ and the corresponding bandmass m are known:
t = m*µ/e
with e as carrier charge. I assume, due to the principe of detailed balance, minority carrier have the same lifetime. Both concentrations are related by
ni2 = p*n
with ni the intrinsic carrier concentration, n the electron and p the hole concentration. If you reduce one electron, you generate holes and vice verca. The product of both carrier species only depends on temperature (of course on the gap and the doping level). But minority and majority carrier concentrations are not independent from each other and therefore not the lifetimes.
Yours
R. Mitdank
Recombination of electrons and holes is a process by which both carriers annihilate each other: electrons occupy - through one or multiple steps - the empty state associated with a hole. Both carriers eventually disappear in the process. The energy difference between the initial and final state of the electron is released in the process. This leads to one possible classification of the recombination processes. In the case of radiative recombination, this energy is emitted in the form of a photon. In the case of non-radiative recombination, it is passed on to one or more phonons and in the case of Auger recombination it is given off in the form of kinetic energy to another electron. Another classification scheme considers the individual energy levels and particles involved.
Band-to-band recombination occurs when an electron moves from its conduction band state into the empty valence band state associated with the hole. This band-to-band transition is typically also a radiative transition in direct bandgap semiconductors.
There are three recombination mechanisms. the radiative Band-Band recombination, the band-trap-band Shockley Reed-Hall recombination and the Auger three particle recombination. The first one is the only one emitting light while the two others loose their recombination energy in kinetic energy form either thermal vibrations or colliding with other mobile particles.
These types are studied intensively in semiconductor literature and one can find rate expressions relating the excess recombination rate with carrier concentration and material proprieties for each type.
For these recombination formula please refer to the book: Book Electronic Devices
I previously formed a researchgate forum about about the recombination of electron hole pairs in semiconductors to discuss this topic: https://www.researchgate.net/post/Generation_recombination_of_electron_hole_pairs_in_semiconductors
Best wishes
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Semiconductor