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ECE132_solved_midterms - ECE 132 Solved Questions from...

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ECE 132 - Solved Questions from Previous Midterms I. Explain (i.e give reasons) whether the following questions are true  or false. 1. Doping Si with a Group V atom (e.g. As) produces two donor levels  E d1  and E d2  below E c False. It produces one donor level. For two donor levels you need two types of  dopants. 2. The closer the donor level to E c , the more effective the doping. True. The closer the donor level is to E c , the less thermal energy is necessary for  electrons to jump to the conduction band from the donor level. 3. For a given drift velocity, the higher the electron mobility, the  higher the electric field. False. So the higher the electron mobility, the lower the electric field. 4. The lower the effective mass, the higher the mobility.
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True. The lower the effective mass of a charge carrier, the easier it is to move  around. 5. np = n i ,always. False. This only holds true in thermal equilibrium.
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