P1. Consider an n-type semiconductor sample. The area of the sampleis 100 m2, an

Question

P1. Consider an n-type semiconductor sample. The area of the sampleis 100 m2, and the
thickness is 400 m. Assume that the mobility is 1000cm2V-1s-1. The sample is doped with
donors with a density of 1016 cm-3.
(a) Find the electron and hole concentrations in this sample. Whichcarrier type will
dominate conduction?
(b) Find the conductivity and resistivity of the sample. Thisdoesn’t depend on the
dimensions.

Explanation / Answer

Here it is given that semi conductor has been doped with doner. Nd=1016 cm-3 Assuming that concentration of intrinsic electrons is negligible ,so electrons concentration = 1016cm3 Also we know , NaNd=Ni2 Ni=intrinsic concentration , So here the material is not given , so we cannot find Ni . Assuming it to be silicon , Ni = 1.1*1010 So Na=Nh = 1.21*104 cm-3 Here Nd>>Na So negative carried will dominate conduction i.e.electrons b) Conductivity = ne       n=1016cm-3         e=charge of eelctron =1.6*10-19C            =mobility= 1000 Putting the values , conductivity = 1.6-1cm-1 resistivity = 1 / conductivity = 0.756 cm=7.56*10-3 m

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