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




None of these
medium
Solution
The electrical conductivity of a semiconductor is given by
.
Where are electron and hole mobilities respectively. Here is negligible compared to . Therefore,
.
.
Because may also be written as S (siemen). Hence
.
SIMILAR QUESTIONS
Pure Si at 300 K has equal electron (n_{e}) and hole (n_{h}) concentrations of . Doping by indium increases n_{h} to . Calculate n_{e} in the dopped Si.
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.
The number of electronhole pairs in an intrinsic semiconductor is at 27^{o}C. If this semiconductor is doped by a donor impurity such that the number of conduction electrons becomes, calculate the number of holes at 27^{o}C. Also calculate the dopant concentration.
In a pure Ge sample at room temperature the electron and hole concentration is each equal to . It is doped with indium, 1 indium atom is added for 10^{6} Ge atoms. Find the conductivity of doped Ge. The concentration of Ge atoms in the sample is . Given :
.
Find the number density (concentration) of donor atoms to be added to an intrinsic germanium semiconductor to produce an ntype semiconductor of conductivity . The mobility of electron in ntype germanium is 3900 cm^{2}V^{–1}s^{–1}. Neglect the contribution of holes to the conductivity.
A semiconductor is known to have an electron concentration of and a hole concentration of . Is the semiconductor ntype or ptype? What is the resistivity of the sample if the electron mobility is 23,000 cm^{2}V^{–1}s^{–1} and hole mobility is 100 cm^{2}V^{–1}s^{–1}.
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 :
.
At absolute zero of temperature, the electrical conductivity of a pure semiconductor is
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?
In a transistor circuit, the collector current is 50 mA and the base current is 1 mA. The current gain is