Which of the following is true? (Only one is true, and explain each one as to wh

Question

Which of the following is true? (Only one is true, and explain each one as to whether it is true/false)

1] In metals, dislocations provide easy pathways for conducting electrons.

2] When a hole is created by thermal excitation of an electron across the band gap (1.1 eV) in silicon (atomic number 14), it has the same charge as a hole created by thermal excitation of an electron across the band gap (0.67 eV) in germanium (atomic number 32).

3] When a reverse-bias potential is applied across a p-n junction in doped Si, the flow of charge carrier across the junction will be insignificantly small.

4] In any given intrinsic semiconductor, the mobility of holes in the construction band is lower than the mobility of electrons in the conduction band.

5] The addition of Ge to Si produces an extrinsic semiconductor.

Explanation / Answer

1. False. Dislocations means a less aligned atomic lattice in metals. Entron transfer is preferred when atoms are aligned so it can be transferred among the same conduction band of side by side atoms.

2.True. In both the cases the atom is losing on electron from valance band. Both has the same charge.

3.True. In reverse bias depletion region doesn't allow flow of current from n to p. But a little current flows due to diffusion.

4.True. Electron mobility in conduction band is greater than hole mobility in valance/construction band i.e. flow of electron in reverse direction. Valance band is nearer to nucleus so its mobility is low.

5.True. Extrinsic means anything which is doped i.e. not pure. Silicon is not generally doped with germanium because atomic size is larger and both have same valency.

I only got one false option.

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