0
Which has greater mobility in intrinsic semiconductor Electrons or holes?
Wiki User
∙ 16y ago
The mobility of electrons is always greater than holes. Only the number of electrons and holes would be same in an intrinsic semiconductor.
Wiki User
∙ 16y ago
Add your answer:
Earn +20 pts
Why is carbon not used as a semiconductor?
semiconductors are silicon and germanium. they are like metals but their highest occupied electron shells/orbitals do not overlap. they require a little energy to exite electrons into the conduction band. Small amounts of group 3 or 5 elements can be changed to dramatically alter conductivity. the structure of carbon allotropes, such as diamond and graphite, do not allow this. Diamond is a covalent network with no free electrons. Graphite is layers of hexagonal carbon networks with electrons allowed to flow in one directing only. Adding these metal impurities, if it can be done easily, will not have the same effect
Why does zener diode have negative temp coeff?
Zener Diodes like all other diodes use a semiconductor P-N junction. The focus of this topic is actually more on the semiconductor characteristics than the diode it self. Semiconductors are not conductors and do not exhibit the same behavior than conductors. In this section free electron band and conductive band are used synonymously and Fermi level is a quantum mechanical term I can roughly define in semiconductor physics for a basic understanding as the kinetic energy of the electron in the highest quantum level. Semiconductors do not have electrons in the conduction band. All electrons are bound in covalent bonds and their valance bands are nearly filled under normal condition. It is required for an external energy to increase the Fermi level of the electrons in the valance energy band to jump the energy gap (forbidden band) into the conduction band. Then the semiconductor becomes conductive. Thermal energy is one type of energy that can raise the Fermi level of the fermions (particularly electrons in this case) in the valance electron band to jump the energy gap into the conduction band. This will increase the probability for an electron to find it self in the conduction band resulting in the semiconductor to become more conductive. In this case we will see that the contribution that thermal energy makes to increase conductivity by raising the Fermi level is much more than the contribution thermal energy makes to increase resistance, by making the atoms vibrate more, increasing collusions between electrons. This cause the semiconductor to form NTC (negative temperature coefficients), The higher the temperature the better it conducts within normal boundaries. With conductors, they already have electrons in conductive bands and by adding energy to it will not make that much difference in the amount of free electrons (conductivity). This cause a very small contribution to increasing conductivity. But the contribution to increase resistances are far greater due to the vibration of the atom causing more collisions between electrons. This give conductors a PTC (positive temperature coefficient) in normal conditions and cause the electrical resistance to increase when temperature increases. One can also take note that not only silicon Si and germanium Ge are semiconductors, but carbon only appear to be a conductor because it conducts electricity and often misunderstood on "school science" level. It is actually a semiconductor and also have NTC (negative temperature coefficients). Graphite can conduct electricity due to the vast electron delocalization within the carbon layers, a phenomenon called aromaticity. These valence electrons are free to move, so are able to conduct electricity. However, the electricity is only conducted within the plane of the layers.
What element has greatest electrode negativity?
Electronegativity: is the ability of an atom to attract the bonding electrons in a covalent bond fluorine is the most electronegative element on the periodic table, and francium is the least, the reasons for this are fairly simple: The factor which affect electro negativity are similar to that of ionisation energy, if you are not familiar with this then here they are - nuclear charge; the greater the charge of the nucleus the more strongly the electrons are held towards the nucleus, thus increasing elecrtonegativity - shielding by inner electrons; the greater the number of shells between the outer electron shell and nucleus the less positive attraction will be 'felt' by the outer electron, as a result the elecrtonegativity decreases - and distance between nucleus and outer electron shell; attraction falls greatly as distance increases between outer electron shell and nucleus as a result as distance increase the elecrtonegativity of the element decreases. As fluorine has a small atoms the closer the nucleus is to the shared outer shell of electrons, so the more its will attract the bonding electrons in a covalent bond. Francium is the least as it has the most shells of the group 1 elements along with the greatest number of electrons, as a result both distance and shielding have been increase causing eleconegativity to decrease significantly.
What unit measures the force that makes electrons move in an electric current?
The force that makes electrons move is a voltage, or potential difference and both are measured in Volts. When electrons move, the rate of movement is current, measured in Amps. The amount of current is dependant on both the resistance in a circuit and the voltage. The higher the resistance, the lower the current. The higher the voltage, the greater the current. The symbol for voltage is "V" and confusingly, the symbol for current is "I". The unit of resistance is the Ohm with the symbol "R" or the Greek symbol for omega.
What is greater -1.03 or -0.03?
1.03 is greater.
How intrinsic semiconductor can be made into extrinsic semiconductor?
at higher values of temperature the intrinsic carrier concentration become comparable to or greater than doping concentration in extrinsic semiconductors. thus majority and minority carrier concentration increases with increase in temperature and it behaves like intrinsic semiconductor.
Why mobility of holes is greater than mobility of electron?
electrons have less effective size than that of holes(which actually are not real)...formula says m(mobility)=drift velocity/electric field=et/m where t is relaxation time.. so mobility is inversely proportional to mass hence e has more mobility.
Why does a semiconductor have fewer electrons than a conductor?
Valence electrons only are able to cross the energy gap in semiconductors since it is greater than that of conductors. That is why semiconductors have fewer free electrons than conductors.
Why does an extrinsic semiconductor behave as an intrinsic semiconductor at elevated temperature?
...It is due to the fact that at higher temperatures, the energy in the semiconductor is greater than Eg by a considerable amount, meaning that the conduction band is more full. At these high temperatures, the dopants' role on electron-hole pairs is negligible.
Why does a semiconductor have fewer free electron than a conductor?
Valence electrons only are able to cross the energy gap in semiconductors since it is greater than that of conductors. That is why semiconductors have fewer free electrons than conductors.
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 adaptation allows vertebrates greater mobility?
Legs...?
Which of these results from greater capital mobility?
Increased foreign investment.
What is meant by greater mobility of resources?
Melting point of objects
Which has a greater attraction for electrons Fluorine or Oxygen?
when compared to oxygen, fluorine has greater electronegativity (greater attraction for shared pair of electrons).
Which has a greater attraction for electrons Ca or O?
Oxygen has a much greater attraction for electrons than calcium does.
Why P-type semiconductors mosfet are not use generally?
in case p type semiconductor mosfet the carriers are holes whose mobility is much less then electrons hence they are not used. when mosfets were introduced originally PMOS was much more common than NMOS, because process for PMOS devices was simpler. but as process methods improved things transitioned to NMOS due to higher speed of operation due to greater carrier mobility (as explained above) and eventually CMOS due to lower power consumption. The same was true for similar reasons with bjts: PNP was easier to make but NPN was faster.
