Sample Cornell Q-exam Questions Collected by Edwin C. Kan

For illustrative purposes only. Degree of difficulty of Q-exam questions varies significantly from professors to professors.

  • Device Physics:
    1. Why is it difficult in general to find shallow dopants and to create Ohmic contacts for wide-bandgap semiconductors? What are the possible directions to look for solution?
    2. What are the basic reasons for GaAs-like materials showing higher electron mobility than Si? Why is it different for hole mobility?
    3. What limits the transconductance of a FET? If an FET works like a current source in a quasi-static circuitry, do we want a large or small current out of the FET for high-frequency applications? What physical effects will limit the circuit frequency?
    4. What are the major physical reasons of short-channel effects in MOSFET? Why and how do we reduce them?
    5. How should we choose the oxide thickness of a MOSFET in a specific technology?
    6. Explain the theorem for effective mass of DOS and of conduction in semiconductors.
    7. What limits the carrier velocity in a semiconductor?
    8. What are the major mechanisms of charging and discharging of an EEPROM cell? What are the trade-offs in device design?
    9. For a RTD, how do you apply the Schrodinger equation to build the N shape IV characteristics?  What is missing in the Schrodinger equation for estimating the IV curve?
    10. For a p-n junction diode, draw the equilibrium diagram.  Then draw the equilibrium diagram in the reverse bias before breakdown (including the quasi-Fermi levels).  If a step voltage of forward bias with 10-20 sec rise time is applied, how does the band diagram change in time?  What happens if we have 10-15 or 10-12 or 10-9 sec rise time?
  • Solid State Circuits:
    1. Design a CMOS differential amplifier with all biasing circuits.  How to establish the inverting input?  How to estimate the common-mode and differential mode gain?  How to estimate the output resistance?  Which transistor will need to consider the Early effect?
    2. What is the trade-offs between dynamic and static circuits in digital logic and memory applications?
    3. Given a circuit diagram with floating capacitors, estimate the major time constant and steady-state voltages.
    4. How can we compensate voltage loss in pass transistors? What are the associated penalty?
    5. What are the general circuit techniques in countering process variation for analog circuit design?
    6. What are the main advantages of CMOS logic? Why do submicron CMOS circuits provide a good alternative for RFIC and MMIC?
  • General:
    1. Estimate the angular momentum of the earch and of the spin of an electron.
    2. Model the movement of a gold fish in a fish tank.
    3. Explain the physical effects behind the Eutectic temperature between two materials.
    4. What are the factors that influence the resonant frequency of a thin-film cantiliver?
    5. If you are using a 2GHz radio, how long you can enter a metal tunnel of 3m by 10m and still hope to receive good signals?
    6. How to establish variance and co-variance in a given measurement set?
Edwin C. Kan(kan@ece.cornell.EDU)
404 Phillips Hall
Cornell University
Ithaca, NY 14853
Last modified: 04/30/2003