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
Who manufacture end fitting? Every system manufacturer creates a range of end fittings designed to be used all along with their own fiber system.

Q. Tunnels through the Earth Assume a straight tunnel is cut from the surface of the earth to the opposite side through the centre. The object is going down the tunnel and a

The operation of a logic gate or circuit can be shown in a table which have all possible inputs and their corresponding output is known as the truth table. To write the truth table


a balloon is filled with 100 kg of helium, and that the velocity is 2.0 m / s what is the external kinetic energy?

Simple 'spring' balance Punch four holes in an old tin lid with a nail, spacing them partially round the circumference. Pass pieces of string by these holes and tie them togeth

An automobile fuel tank is filled to the brim with45 L of gasoline (12 gal) at 20°C.Immediately afterward, the vehicle is parked in the sunlight, where the temperature is 45°C. How

COMPARATOR EQUATION USED TO DETERMINE THE CONCENTRATION OF ELEMENTS

The Michelson interferometer was designed to study the nature of: a) water waves b) sound waves c) an "ether" d) sunlight Ans: The Michelson inte

why moseley work on electron x ray spectrum