ECE103_midterm_1W09

# ECE103_midterm_1W09 - 2. [12 points] Determine the surface...

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Midterm Exam 1 ECE103 2/3/09 ALLOWED: Calculators and one 8.5”x11 page of notes (one side). Note you are required to turn in your page of notes with our exam. NOT ALLOWED: Textbooks, class notes, problem sets, etc. ATTEMPT ALL PROBLEMS AND SHOW ALL WORK! This exam has a maximum score of 100 points. You have 80 minutes to complete this exam. q = 1.60x10 -19 C; k = 8.617x10 -5 eV/K; m 0 = 9.11x10 -31 kg; ε 0 = 8.85x10 -14 F/cm; 1 μ m = 1x10 -4 cm = 1x10 -6 m; n i (Si, T=300K) = 1.0x10 10 cm -3 ; E g (Si at T=300K) = 1.12 eV; n i (GaAs, T=300K) = 2.2x10 6 cm -3 ; E g (GaAs at T=300K) = 1.42 eV. 1. BE CONCISE and do not write an essay! The ideal answer for each may be stated in a few sentences. (a) [9 points] Define an insulator, semiconductor, and metal in terms of conductivity and bandgap. Draw the energy band diagrams for insulator, semiconductor and metal. (b) [8 points] What is the law of mass action? Why is it only valid for nondegenerate semiconductors? (c) [ 6 points] What is the charge neutrality relationship for Si at room temperature? 0K? and 800K?
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Unformatted text preview: 2. [12 points] Determine the surface density of atoms for Si on the (a) (100) plane, (b) (110) plane, and (c) (111) plane. 3. [35 points] At T=300K, Si atoms, at a concentration of 10 10 cm-3 , are added to GaAs. Assume that the Si atoms act as fully ionized dopant atoms, and that 10% of the concentration added replace Ga atoms and 90% replace As atoms. (a) Determine the donor and acceptor concentration. (b) Calculate the thermal equilibrium values of electron and hole concentrations. (c) Under an applied E-field of 10V/cm, calculate the electron, hole, and total drift current density. 4. [30 points] The electron concentration in a piece of n-Si varies linearly from 10 17 cm-3 at x=0 to 6x10 16 cm-3 at x=4 μ m. There is no applied electric field. The electron current density is measured to be -400 A/cm 2 . What is the electron diffusion coefficient? Calculate the electron mobility and life time (effective mass, M * n = 0.067 m )....
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## This note was uploaded on 04/02/2011 for the course ECE 103 taught by Professor Song during the Spring '11 term at UCSB.

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