problem 1
The mobility of free electrons and holes for pure silicon are 0.13 and 0.05 m^{2}/V-S respectively. Find the intrinsic conductivity for silicon. Supposing ni = 1.5x 10^{16}/cm^{3} at room temperature.
Use the relation: σ = q.n_{i} (µ_{n} + µ_{p})
problem 2
The mobility of free electrons and holes in pure germanium are 0.38 and 0.18 m2/V_{-s}. Find the intrinsic conductivity for germanium. Supposing n_{i} = 2.5x 1019/m3 at room temperature.
Use the relation: σ = q.ni (µ_{n} + µ_{p})
problem 3
A specimen of silicon is 0.2 mm long and has a cross-section of 0.2 x 0.2 mm. One volt connected across this bar results in a current of 8 mA. Supposing that the current is because of electrons, find out (a) concentrations of free electrons and (b) the drift velocity. The room temperature value of mobility is: µn = 1300 cm^{2}/V-S
problem 4
In a germanium sample, a donor impurity is added to the extent of 1 atom per 10^{8} germanium atoms. Show that the resistivity of the germanium sample drops to 3.7 ohm-cm.
Given: µn = 3800 cm^{2}/V-S and µ_{p} = 1800 cm^{2}/V-S and n_{i} = 2.5x 10^{13}/cm^{3} at room temperature, Nger = 4.41x 10^{22} /cm^{3}
problem 5
An N-type semiconductor has a resistivity of 20 x 10^{-2} ohm-m. The mobility of the electrons through a separate experiment was found to be 100 x 10^{-4} m^{2}/V-S. Find the electron concentration in this material.