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Q.8 A sample of germanium is doped to the extent of 1014 donor atoms per cm3 and 7 × 1013 acceptor atoms per cm3. The resistivity of pure germanises at the temperature of the sample is 60  Ω  cm. Find the total conduction current density due to an applied electric field of 2 V cm–1. The electron and hole mobilities are given to be 3800 cm2 V–1 S–1 and 1800 cm2 V–1 S –1, respectively. (Ans. 52.3 mA cm–2)

Q.9 The energy gap in germanium is 0.75 eV. Compare the intrinsic conductivities of germanium at 300 K and 330 K. Take kB  = 8.6 × 10 –5 eVK–1.     (Ans. 3.74)

Dear studentQ no. 9σ=Ke-Eg2kBTassumig Eg does not change with tempσ1=Ke-Eg2kBT1σ2=Ke-Eg2kBT2Taking ratioσ1σ2=Ke-Eg2kBT1Ke-Eg2kBT2σ1σ2=e-Eg2kBT1--Eg2kBT2σ1σ2=e-Eg2kB1T1-1T2σ1σ2=e-0.752×8.6×10-51300-1330=3.74(all symbols have usual meanins)Regards 
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