Review Questions

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Table of Contents - Glossary - Study Aids
Questions related to:
  1. Introduction
  2. Semiconductor Fundamentals
  3. The Metal-Semiconductor Junction
  4. The p-n diode
  5. The Bipolar Transistor
  6. The MOS Capacitor
  7. The MOSFET
  8. Comprehensive Questions

Introduction

  1. What is the driving force behind the semiconductor industry?
  2. Why is silicon the material of choice when making integrated circuits?
  3. Name three advantages of smaller devices.
  4. What do the following acronyms stand for: MOSFET, CMOS?
  5. Who invented the MOSFET?

Semiconductor Fundamentals

  1. Draw the (632) plane and justify your answer.
  2. Name and draw two different directions in the (110) plane.
  3. Find the maximum filling factor in a body centered cubic lattice (treat the atoms as rigid spheres).
  4. Name a donor and acceptor for GaAs (zincblende lattice) and justify your answer based on the number of atoms in the outer shell
  5. How do we know that the energy of an electron in the hydrogen atom is quantized?
  6. Write an expression relating the two longest wavelengths of the Balmer series to the longest wavelength of the Paschen series
  7. What is the difference between a state and an energy level?
  8. Why is the density of states in k-space constant for all semiconductors?
  9. Two identical atoms separated by a large distance from each other are measured to have the same lowest energy. Does this statement violate the Pauli exclusion principle?
  10. Consider an electron with effective mass m* = m0 which occupies the lowest energy level in an infinite quantum well with Lx = 10 nm. Derive an expression for the charge density distribution in the well and plot it.
  11. Why do the discreet atomic energy levels form energy bands as they are brought together in a crystal?
  12. As holes simply correspond to missing electrons why do we even bother to call them holes?
  13. Why are we so interested in the almost filled and almost empty bands of a semiconductor?
  14. The Fermi function provides the probability of occupancy of a particular energy level requiring only the Fermi energy and the energy of the energy level, but is independent of the density of available states. How can that be?

The p-n diode


The MOS Capacitor

  1. Plot 1/C2 versus VG for an MOS capacitor. Find an expression for the slope and the intercept of the straight line which fits this curve in "depletion".

The MOSFET

  1. Name the four terminals of a MOSFET and describe their function.
  2. What is an "inversion" layer?
  3. What is the doping type of the source, drain and substrate of a p-type MOSFET?
  4. Is the overlap of the gate with the source and drain regions required, beneficial or irrelevant?
  5. Can you explain why an enhancement-mode MOSFET is also called a normally- off MOSFET?
  6. How do you explain that the drain current is at first proportional to the drain- source voltage?
  7. How small must the drain-source voltage be for the linear model to be valid?
  8. What are the basic assumptions of the quadratic model?
  9. Can the quadratic model still used to describe an n-type MOSFET biased with a negative drain voltage? Explain your answer.
  10. Why can we not use the same expression to describe a MOSFET in the quadratic and saturation regime? Use the quadratic model of an n-type MOSFET and explain what happens within the device at VDS = VG - VT.
  11. Why is the current calculated by the variable depletion layer model always larger than that of the quadratic model?

Comprehensive Questions

  1. Why does the p-n diode between the substrate and the drain not block the flow of electrons between the source and the drain?