In part A of the figure there are two squares that are not touching. The one on the left contains a large number of dots indicating electrons. The one on the right contains a large number of small circles indicating holes. Both squares are evenly filled. In part B the two squares have been pushed together to form a larger rectangle. A line down the center indicates the PN junction, the place where the borders of the two squares touch. The dots and circles no longer come up to the center line but there is some empty space on either side of the line. Above the rectangle is a graph having a single horizontal line to mark the axis. The horizontal axis is the physical length of the diode and the vertical axis is electrical potential. The graph line starts at the left end of the diode at zero potential. It rises slowly moving to the right and reaches its maximum in the empty space just to the left of the center line. Then it quickly falls passing through zero at the junction and reaching a negative peak in the empty space just to the right of the junction line. Then it slowly returns to zero at the right end of the diode. The center line represents the junction. End verbal description.
go back.