Discussion Questions are meant to be completed when they are reached in the reading, before continuing.  Getting the "correct" answer to Discussion Questions is not important.  Instead, the purpose of Discussion Questions is to address the issues, start you thinking about the material, and identify your preconceptions.  Completing these assignments before continuing with the reading will aid you greatly in the learning process.
 

Most semiconductor technology is based on silicon.  Often, however, regions of a chip contain silicon "doped" with a small percentage of aluminum,  phosphorus, or other materials.  Look at a periodic table.  Where does aluminum fall in the table?  Where does phosphorus fall in the table?  Where is silicon?  Do you expect the effects of aluminum in silicon to be similar  or opposite to the effects of phosphorus in silicon?  Why? Now look at where gallium falls in the periodic table, compared to silicon and to phosphorus.  Do you expect the effects of gallium in silicon to be similar  or opposite to the effects of aluminum in silicon?  Why? A diode, shown in the image to the right, is a device that allows current to only pass in one direction.  If a battery were to be hooked up in the "wrong" direction, no current would flow.  But if the battery were hooked up in the "right" direction, current would flow easily through the diode.  Can you think of situations where such current regulation might be useful?  Diodes such as the one pictured to the right rely unique properties of doped silicon. Conduction in semiconductors not only depends upon the motion of electrons, it also depends upon the motion of something called "holes".  Think back to the last frame of the simulation of conduction in semiconductors.  Can you see what might be a hole?  How could those holes move through the material?

What is a "hole"?  Go to the next page to find out!