## Question

### Solution

Correct option is

The concentration of indium (acceptor) atoms in the sample is

Since one acceptor atom provides one hole, the concentration of the holes provides is , that is

For a doped semiconductor, we have

Where ni is the intrinsic concentration. Thus, the electron concentration in the doped semiconductor is

The electrical conductivity of the doped Ge is given by

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#### SIMILAR QUESTIONS

Q1

Pure Si at 300 K has equal electron (ne) and hole (nh) concentrations of . Doping by indium increases nh to . Calculate ne in the dopped Si.

Q2

A semiconductor has equal electron and hole concentrations of . On doping with a certain impurity, the hole concentration increases to . Calculate the new electron concentration of the semiconductor.

Q3

The number of electron-hole pairs in an intrinsic semiconductor is  at 27oC. If this semiconductor is doped by a donor impurity such that the number of conduction electrons becomes, calculate the number of holes at 27oC. Also calculate the dopant concentration.

Q4

A semiconductor has an electron concentration of m–3 and a hole concentration of . Calculate its conductivity. Given : electron mobility , hole mobility

Q5

Find the number density (concentration) of donor atoms to be added to an intrinsic germanium semiconductor to produce an n-type semiconductor of conductivity . The mobility of electron in n-type germanium is 3900 cm2V–1s–1. Neglect the contribution of holes to the conductivity.

Q6

A semiconductor is known to have an electron concentration of  and a hole concentration of . Is the semiconductor n-type or p-type? What is the resistivity of the sample if the electron mobility is 23,000 cm2V–1s–1 and hole mobility is 100 cm2V–1s–1.

Q7

The electrical conductivity of  a semiconductor inceases when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it. Find the band gap for the semiconductor. Given :

.

Q8

At absolute zero of temperature, the electrical conductivity of a pure semiconductor is

Q9

In pure silicon at 300 K the electron and hole concentration is each equal to . When doped with indium, the hole concentration increases to . What is the electron concentration in doped silicon?

Q10

In a transistor circuit, the collector current is 50 mA and the base current is 1 mA. The current gain  is