Effects of Impurities

Record the color of the LED you were assigned and the energy (in eV) of the energy gap.

Now, click on the Add Impurities button. This action places acceptors in the left block and donors in the right block. Record answers to the following materials.

• How does adding acceptors — atoms with fewer electrons — affect the energy bands of the left block?
• What is the effect on the energy bands of adding donor atoms to the right block?
• Do the sizes of the energy gaps for either semiconductor block change as donor or acceptor atoms are added?
• A material that has donor atoms has more electrons than one with acceptors. When these two materials are joined together, the electrons can move from one material to the other. Which way would you expect the electrons to move? Why?