1–20(a). As you can see, the valence and conduction bands in the n region are at lower energy
levels than those in the p region, but there is a significant amount of overlapping.
The free electrons in the n region that occupy the upper part of the conduction band in
terms of their energy can easily diffuse across the junction (they do not have to gain additional
energy) and temporarily become free electrons in the lower part of the p-region conduction
band. After crossing the junction, the electrons quickly lose energy and fall into