1. What are the majority carriers of electric curent in Boron-doped Silicon? a)
ID: 2086398 • Letter: 1
Question
1. What are the majority carriers of electric curent in Boron-doped Silicon? a) Holes b) Electrons c) Boron ions d) Silicon atoms 2. Cold-worked aluminum has a higher electrical resistivity than annealed alumimm. This is because a) cold-worked Al has a higher strength so the resistivity is increased b) cold-worked Al has a higher dislocation density so the resistivity is increased c) the martensite that forms in cold-worked Al natrally has a higher resistivity d) the grains are aligned from cold-work and the alignment causes the resistivity to increase 3. The addition of a boron (B) impurity to otherwise pure silicon (Si) will a) Decrease conductivity due to additional scattering of electrons due to the impurity b) Create an additional allowable energy level inside the band-gap called an acceptor level c) Create an extrinsic semiconductor with the majority charge carrier being a hole instead of an electron d) All of the above e) A and B only f A and C only g B and C only 4. What would you predict would result from adding a small amount of nitrogen (called "doping) to an otherwise pure silicon material? a) The nitrogen impurity will increase resistivity b) Nitrogen will create vacancies that will decrease resistivity c) Nitrogen is a gas and should have no impact on the electronic properties of the silicon d) Nitrogen will create a "donor level" in the band structure that results in an n-type extrinsic semiconductor e) Nitrogen will create an "acceptor level" in the band structure that results in a p-type extrinsic semiconductor Nitrogen will make the silicon more intrinsic which will cause a decrease in resistivity f) 5. Assuming the electrical conductivity of pue silver is higher than pure copper, what would you predict would result from adding-05wt% silver to an otherwise pure copper material? a) b) c) d) Conductivity will increase Conductivity will decrease Conductivity will not change It's impossible to predict without more informationExplanation / Answer
1. Boron is a tri valent element whereas silicon is a four valent element. Due to lack of electron in boron, during doping it will create holes which are majority carriers:answer a
2. Due to alignment of grains, the resistivity of cold worked aluminium is higher. Answer d
3. Adding boron to silicon to form an extrinsic semi conductor to increase the conductivity of silicon. This is also creates an acceptor level. Answer g.
4.Nitrogen is a penta valent elements. On doping it will creat extra elections. Thus it creates a donor level and from n type semi conductor.
5. Small portion i.e. below 1% addition of silver increase the conductivity of copper
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