Download Electrons - Microelectronic Devices and Circuits - Exam and more Exams Microeconomics in PDF only on Docsity! Microelectronic Devices and Circuits- EECS 105 First Midterm Exam Wednesday, October 11, 2000 Costas J. Spanos University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Science Problem 1 of 4 (35 pts) Answer each question briefly and clearly. Assume room temperature and thermal equilibrium unless otherwise noted. What types and concentrations of charges exist in intrinsic silicon? (6 pts) List the type (holes, electrons, ions), sign (+/-) and concentrations of all charges in silicon doped with 10^17/cm^3 As and 10^15/cm^3 Boron. Be sure to mention whether each charge is mobile or not. (8 pts) What are the four types of currents you can find across a p-n junction in thermal equilibrium? (6 pts) Find the contact-to-contact resistance of the following structure (drawn to scale), if the Rs is 10 ohms/square. Assume that "dogbone" contact areas amount to 0.65 squares. (8pts) midterm1 1 You are given doped silicon that at thermal equilibrium has an electron concentration 10^16/cm^3. What is the built-in potential with reference to intrinsic silicon? What would be the concentration of electrons at some point within this lattice, if you raised the potential at that point by 120mV? (7 pts) Problem 2 of 4 (35 pts) Consider the following structure that consists of n-type silicon (10^16/cm^3), 0.1 micrometers of SiO2 and p-type silicon (10^16/cm^3). (Hint: This is nothing more than a MOS capacitor whose gate is made out of weakly doped silicon. This means that the gate will also deplete and/or invert under proper conditions. The symmetric concentrations in the channel and the gate should make this problem easy to solve...) a. Calculate the depth of the depletion regions when Vgb = 0 (10 pts) b. Draw the density, E-field and potential plots in thermal equilibrium (Vgb = 0). Mark the key values on the charge densities, Electric Fields, and potential graphs. (If you failed to solve part a, do these plots anyway, assuming that each depletion region has a depth of 0.1 micrometers. Please check this box if you opt to use this value: PUT BOX HERE) (7 pts) midterm1 2
