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.


Correct option is


The electron concentration  in the semiconductor is higher than the hole concentration . Hence the semiconductor is n-type. 

The resistivity  of a doped semiconductor is given by 


 are electron and hole mobilities respectively. 










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.


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 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.  


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


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 106 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 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.


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