Direct and indirect recombination, Physics

The recombination procedure is represented with returning the electron from the CB where it is free into a hole in the VB where it is in a bond. The excess energy of the electron is lost as a photon of energy. This type of recombination results in the emitted light from light emitting diodes. The recombination process between an electron and a hole like every other process in nature, must obey the conservation law of energy. The wave function of an electron in the CB will have the momentum and similarly electron wave function in the VB will have a momentum. Conservation of linear momentum during recombination process requires that when the electron drops from the CB to the VB, its wave vector remain the same, Kvb= Kcb. The states with this are right at the top of the valance band, they are essentially empty (certain holes) this kind of recombination is called Direct Recombination. This type of recombination is highly probable in gallium arsenide etc. In elemental semiconductor crystal for example Si and Gallium the minimum or lowest energy of CB is not directly above the maximum of the VB. Hence, electron at the bottom of the CB there fore cannot recombine directly with a hole at the top of the VB. The law of conservation of momentum is not allowed in this case and therefore momentum is not allowed in this case and therefore momentum must change. The recombination process in these elemental semiconductors occurs via a recombination centres at an energy level E which is represented below Ec in the band gap. When an electron approaches the centre at Er, it is captured. The electron is then localized and bound to this centre and “waits” therefore for a hole with which it can recombine. And then it can fall down into the top of the VB. The energy of electron is lost to lattice vibration (as sound) via the recoiling of the body (recombination centre). Emitted lattice vibrations are known as phonons. A phonon is a quantum of energy associated with atomic vibrations in the crystals analogues to the photon.

Posted Date: 7/7/2012 9:19:51 AM | Location : United States







Related Discussions:- Direct and indirect recombination, Assignment Help, Ask Question on Direct and indirect recombination, Get Answer, Expert's Help, Direct and indirect recombination Discussions

Write discussion on Direct and indirect recombination
Your posts are moderated
Related Questions
Advantages of D.C. transmission of power  1. It needs only two conductors as compared to three for a.c. transmission. 2. There is not an inductance, capacitance, phase displ

Figure shows a simple model of spring-mass system. The mass is released from the rest with the springs un-stretched. It's downward acceleration is a=9.81 - 15.24y m/s 2 where y is

Phenomenon of resonance At resonance, rapid transfer of energy takes place resulting louder sound (booming sound). If two bodies having same natural frequency is placed side b

Describe specific charge? Desfine Thomson's experiment to calculate e/m of an electron with relevant theory.

Visible Radiation (Waves): Visible waves have a wavelength range among 400 and 700 nanometre.

give the complete explaination with design formulae of single pv cell?

Q. Action to be made if the resistance to earth of earth electrode is high? Ans: Earth resistance lies upon soil conductivity. To reduce earth resistance dig around the earth

Light is normally incident on a thin soap film and is reflected.  If the wavelength of this light is "L" and the index of refraction of the soap film is "N", complete destructive i

A diffraction grating with slits separated by 3.40 x 10 -6 m is illuminated by light with a wavelength of 589 nm. The separation between lines in the diffraction pattern is 0

explain with the aid of a diagram what is meant by the moment of a force about point