Home
Class 12
PHYSICS
The concentration of hole-electron pairs...

The concentration of hole-electron pairs in pure silicon at T=300K is `7xx10^(15)`per cubic metre, Antimony is doped into silicon in a proportion of 1 atom in `10^7`atons. Assuming that half of the impurity atons contribute electrons in the conduction band, calculate the foctor by which the number of silicon atoms per cubic metre is `5xx10^(28)`

Text Solution

Verified by Experts

The number of charge carries before doping is equal to the number of holes plus the number of charge carriers per cubic metre before doping
`2xx7xx10^(15)=14xx10^(15).`
Since antimony is doped in a proportion of 1 in `10^(7)`,the number of antimony atoms per cubic metre is `10^(-7)xx5xx10^(28)=5xx10^(21)`.As half of these atoms contribute electrons to the conduction band,teh number of extra conduction electrons produced is `2.5xx10^(21)`per cubic metre after the doping is
`2.5xx10^(21)+14xx10^(15)`
`~~2.5xx10^(21)`
The factor by which the number of charge is increased
`=(2.5xx10^(21))/(14xx10^(15))=1.8xx10^(5).`
In fact, as the n-type impurity is doped ,the number of holes and conduction electrons remains almost the same.However this does not affect our result as the number of holes is anyway to small as compared to the number of conduction electrons.
Promotional Banner

Topper's Solved these Questions

  • SEMICONDUCTOR AND SEMICONDUCTOR DEVICES

    HC VERMA|Exercise Question for short answer|10 Videos

  • SEMICONDUCTOR AND SEMICONDUCTOR DEVICES

    HC VERMA|Exercise objective I|15 Videos

  • SEMICONDUCTOR AND SEMICONDUCTOR DEVICES

    HC VERMA|Exercise exercises|35 Videos

  • PHOTOMETRY

    HC VERMA|Exercise All Questions|44 Videos

  • SPEED OF LIGHT

    HC VERMA|Exercise Exercises|3 Videos

Similar Questions

Explore conceptually related problems

A copper wire has a resistance of 10Omega and an area of cross-section 1 m m^(2) . A potential difference of 10 V exists across the wire. Calculate the drift speed of electrons if the number of electrons per cubic metre in copper is 8xx10^(28) electrons.

Estimate the proportion of boron impurity which will increase the conductivity of a pure silicon sample by a factor of 100.Assume that each boron atom creates a hole and the concentration of holes in pure silicon at the same temperature is 7xx10^15 holes per cubic meter. Density of silicon is 5xx10^28 atoms per cubic metre.

The product of the hole concentration and the conduction electron concentration turns out to be independent of the amount of any impurity doped. The concentration of conduction electrons in germanium is 6xx10^19 per cubic metre. When some phosphorus impurity is doped into a germanium sample, the concentration of conduction electrons increases to 2xx10^23 per cubic metre.Find the concentration of the holes in the doped germanium.

In a pure semiconductor the number of conduction electrons is 6xx10^(19) per cubic metre.How many holes are there in a sample of size 1cmxx1cmxx1mm?

Let (Delta)E denote the energy gap between the valence band and the conduction band.The population of conduction electrons (and of the holes)is roughly proportional to e^(-Delta E//2kT). Find the ratio of the concentration of conduction electrons in diamond to that in silicon at room tempareture 300K. (Delta E) for silicon is 1.1 ev and for diamond is 6.0eV.How many conduction electrons are likely to be in one cubic meter of diamond ?

A copper wire of 10^(-6)m^(2) are of cross section, carries a current of 2A. If the number of electrons per cubic meter is 8xx10^(28) , calculate the current density and average drift velocity.

A tightly- wound , long solenoid carries a current of 2.00 A. An electron is found to execute a uniform circular motion inside the solenoid with a frequency of (1.00 xx 10^8 rev s^-1 ). Find the number of turns per metre in the solenoid.

Suppose a pure Si crystal has 5 xx 10^(22) atoms m^(-3) . It is doped by 1 ppm concentration of pentavalent . As . Calculate the number of electrons and holes . Given that n_(i) = 1.5 xx 10^(16) m^-3 .