# Worksheet: Pure Semiconductors

In this worksheet, we will practice describing the electrical bonds in pure semiconductor materials.

Q1:

The diagram below shows a lattice of atoms where a free electron is adjacent to a vacancy. Which of the following diagrams most correctly represents the lattice a short time later? • A • B • C • D • E Q2:

In a pure semiconductor at a temperature of 320 K, the number of free electrons in the semiconductor is . The temperature of the semiconductor is increased to 420 K. Which of the following correctly describes how changes? The semiconductor is in thermal equilibrium at both temperatures.

• A remains constant.
• B increases.
• C decreases.

Q3:

The following diagrams show a lattice of atoms. Which of the diagrams shows the lattice at a higher temperature?

• A • B • CBoth diagrams show the lattice at the same temperature.

Q4:

In a pure semiconductor at a temperature of 320 K, the rate at which electrons in the semiconductor become free electrons is and the rate at which holes form in the semiconductor is . The temperature of the semiconductor is reduced to 280 K. What is the ratio of to ? The semiconductor is in thermal equilibrium at both temperatures.

Q5:

In a pure semiconductor at a temperature of 320 K, the number of free electrons in the semiconductor is and the number of holes in the semiconductor is . The temperature of the semiconductor is reduced to 280 K. What is the ratio of to ? The semiconductor is in thermal equilibrium at both temperatures.

Q6:

In a lattice of atoms, an electron in the outermost shell of an atom gains sufficient energy to become a free electron, leaving a vacancy in the shell. The vacancy is then filled by a different electron. Which of the following could be the source of the electron that fills the vacancy?

• AA bound electron from a shell other than the outermost shell of the atom from which the free electron was produced
• BA bound electron from a shell other than the outermost shell of an atom bonded with the atom from which the free electron was produced
• CA bound electron from the outermost shell of an atom bonded with the atom from which the free electron was produced
• DA bound electron from the outermost shell of the atom from which the free electron was produced
• EAnother free electron in the lattice

Q7:

In a lattice of atoms, an electron in the outermost shell of an atom gains sufficient energy to become a free electron, leaving a vacancy in the shell. Which of the following events is most likely to occur next in the lattice a short time interval after the electron becomes free?

• AThe free electron and the vacancy will recombine.
• BAnother free electron and vacancy will be produced.