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What effect do added impurities have on semiconductor conductivity?
It is called as DOPING. Doping is the process in which you add an impurity to a pure semiconductor to increase its conductivity. While doping is done, crystal structure of semiconductor is not disturbed.
Why Si is semiconductor and Cu is conductor?
silicon has 4 valence electrons leaving a half empty shell sharing electrons covalently with its neighbors leaving no free electrons, copper has 1 valence electron which is so loosely bound it forms an electron gas which conducts easily. silicon can be doped with tiny amounts of impurities having 5 or 3 valence electrons, providing free electron or missing electrons called holes to carry current.
What is the term valance band?
It refers to the energy levels in an atom where the electrons that participate in bonding occupy. These energy levels correspond to those of the s and p orbitals of the outermost shell of the atom being considered.
Why n type and p type semiconductors have gauge factor as negative and positive respectively?
An n-type semiconductor is typically pure silicon, doped with a Group 5 element, such as gallium. Silicon has four (4) electrons in its valence shell, while gallium has five (5). Therefore, when they bond, the fifth electron is promoted to the conduction band as the other 4 have been filled up. This is also called a donor atom. Now, since there are free electrons in the conduction band, they carry 'extra' negative charge. Thus, it is called an n-type semiconductor. The p-type semiconductor is similar, except a Group 3 element is used, such as boron. This has 3 valence electrons, creating a positive charge carrier (hole) in the lattice. Thus, there are more positive 'charges,' making it a p-type semiconductor.
Why is the mobility of electrons greater than the mobility of holes?
In an intrinsic semiconductor, a few electrons get thermally excited and break from their valence bond to become a free electron. This leaves behind a vacancy in its place called 'hole'. In a P-type semiconductor, B with 3 electrons replaces a Si atom with 4 electrons in the lattice. 3 covalent bonds are formed by B with 3 neighbouring Si. But there is a deficiency of one electron in B for bonding with the 4th Si. This deficiency/vacancy is called a hole. When an electric potential difference is present, the electrons from adjacent valence bond moves into the vacancy near it while moving along the potential. The following represents the movement of valence electron. Terminology: * represents valence electron _ represents hole A is -ve and B is +ve. ..I A * * * _ * * * B .II A * * _ * * * * B III A * _ * * * * * B .IV A _ * * * * * * B I- Hole is at the 4th position. II- At first, the 3rd electron from left shifts right to fill the vacancy and leaves behind a vacancy in its place. The vacancy is at the 3rd position. III- Next, the 2nd electron from left has shifted to the 3rd place and filled up that vacancy but leaves a vacancy at its place. The vacancy is at 2nd position. IV- Now, the 1st electron from left moves to occupy the vacancy at the 2nd position creating another vacancy in its own place. The vacancy is at 1st position. As the electrons moved right, the vacancy moved left. The vacancy is called a hole (just a shorter name for convenience). The movement of holes is really the movement of electron in the valence band. Therefore, the mobility of a hole is indirectly the mobility of valence electrons. Mobility is the velocity acquired per unit electric field. In the intrinsic and N type semiconductors, many free electrons are present i.e. electrons in conduction band which are free to move in the crystal as against valence electrons which can only move in the lattice points. When an electric field is applied, both the valence electrons and the free electrons move in the same direction. The hole direction is opposite to that of valence electron but the mobility is the same, as explained earlier. Even for the same electric field, valence electrons cannot move as freely as the free electrons because its movement is restricted. Therefore, the velocity of valence electrons is less compared to free electrons. In other words, the velocity of holes is less compared to free electrons. This means mobility is also less for a hole compared to free electron. Thus, mobility of a free-electron (often abbreviated as 'electron') is greater than that of a hole (indirectly referring to valence electron).
What are atoms valence electrons?
the electrons on their outer shell, all atoms want to gain a full valence shell.
The chemical properties of an atom depend on the number of what?
The chemical properties of an atom depend on the number of electrons in its outermost shell, known as the valence electrons. These electrons determine how atoms interact with other atoms to form chemical bonds.
What do you mean by valence shell and valence electrons?
The valence electrons are involved in the chemical bonding of atoms in a molecule.
What determines whether or not an atom reacts with other atoms is it the electrons on the first shell or the second?
It is predominantly the electrons on the outermost shell (valence electrons) of an atom that determine its reactivity with other atoms. These valence electrons are involved in forming chemical bonds with other atoms.
What are the electrons in the outermost electron shell or orbital called?
The electrons in the outermost shell or orbital are called valence electrons. These electrons are involved in forming chemical bonds with other atoms.
What is the electron called when the electrons in the outer shell of atoms?
These are the valence electrons.
How many electrons do silicon atoms have?
14 electrons. 2 electrons in the first shell, 8 electrons in second shell, and 4 electrons in the valence shell.
What are the electrons the outermost shell of an electron called?
Valence electrons are the electrons in the outermost shell of an atom. The ones in the inner shell are known as core electrons.
The electrons found in atoms outer shell are often called what?
Valence Electrons
What is the name given to the outer shell of the atom?
The outer shell of an atom is the valence shell, which contains the valence electrons.
Which electrons are use to form bonds?
Valence electrons are the electrons that are used to form bonds between atoms. These are the electrons in the outermost shell of an atom.
What are electrons found in an atoms outer shell called what?
The electrons in the outermost shell is called as valence electron. These electrons are free and they are involved in bonding reactions.
