Why is mobility of electrons and holes different?

Why is mobility of electrons and holes different?

Since holes are subjected to the stronger atomic force pulled by the nucleus than the electrons residing in the higher shells or farther shells, holes have a lower mobility. because electron effective mass is smaller than holes therefore mobility of electron is higher than holes.

Why mobility of electron is greater than mobility of holes?

The electron mobilty is often greater than hole mobility because quite often, the electron effective mass is smaller than hole effective mass. The relaxation times are often of the same order of magnitude for electrons and holes and therefore, they do not make too much difference.

What is the effect of electric field on mobility?

Electric field dependence and velocity saturation At low fields, the drift velocity vd is proportional to the electric field E, so mobility μ is constant. This value of μ is called the low-field mobility.

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Why effective mass of electron is less than hole?

The only difference between electrons and holes is in their energy and, therefore, in velocity. The effective mass is a result of electron interaction with lattice, i.e. with phonons. As the hole velocity is smaller, a hole spends more time in the interaction region, i.e. holes strongly interact with phonons.

What is hole effect?

The Hall effect is the deflection of electrons (holes) in an n-type (p-type) semiconductor with current flowing perpendicular to a magnetic field. The deflection of these charged carriers sets up a voltage, called the Hall voltage, whose polarity depends on the effective charge of the carrier.

What is mobility Hall effect?

The thermoelectric voltage arises from contacts between two different materials. It is independent of the current, but it does depend on the thermal gradients present. The mobility (μ) is the Hall coefficient divided by the resistivity.

Why is the mobility of electrons in conduction band is more than the mobility of electrons in valence band?

Answer: Free electrons, those are moving from one atom to another are in conduction band. Conduction band is at higher energy level than valance band. Hence electron at Conduction band moves faster and has more mobility than holes in valance band.

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What is mobility of an electron?

The measurement of how fast an electron can move through a semiconductor or a metal which is under the influence of an external electric field is known as electron mobility. We can show electron mobility mathematically by the equation, μ=VdE .

What is effective mass of electron and hole?

The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg).

What is the difference between mass and effective mass?

Free electron mass is the actual mass of an electron which is equal to kilograms. Effective mass is the mass that a particle seems to have when it is interacting with other particles.

What do you mean by mobility of charge carriers?

The mobility of a charge carrier is defined as the drift velocity of the charge carrier per unit electric field. Thus, mobility , μ=Evd​​ If q be the charge of carrier and τ be the relaxation time, then mobility μ=mqτ​ where m be the mass of the charge carrier.

Why is hole mobility generally lower than electron mobility in semiconductors?

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However, the reason why hole mobility is “generally” lower than electron mobility is the band gap in electronic structure of semiconductors that keeps the conduction band (where electrons move around in it) basically empty, and the valence band (where holes move around in it) basically

What is meant by the term mobility of electron?

Mobility is the speed (velocity) of movement of a particle (an electron or a hole) per unit Electric field (in low field situations). So this movement of vacancies (hole) is ‘harder’ than the movement of electrons, which are not in bound states.

What is the meaning of hole mobility?

Holes are simply vacancies, they move when electron from one position move to available hole. Thus the hole which was in pos1 is now effectively in pos2…thus we say the hole has “moved”. Thus hole mobility measurement is obviously a measurement of how fast an electron can vacate a position and occupy another.

What is the difference between an electron and a hole?

It is due to smaller effective mass of electron as compared to that of hole. Electrons more freely, have greater drift velocity, greater mobility. The electron’s effective mass is tied to the energy of the valence band while the hole’s effective mass is tied to the conduction band of the material.