april,
... hole theory is getting less used and comes with more explanations these days but is still pretty much balderdash to cover a reluctance to show current (electron) flow correctly
Where appropriate, holes cannot be ignored anymore than electrons can. In fact, at the quantum level for semiconductors, holes have the same status, and are thought of as particles. Before I correct the misconceptions propagated by Forrest Mims, let me say a few things about charge flow. It is wrong to define mathematically, current direction by the direction of charge movement. That is because there are two kinds of charges that move in response to a voltage field. It is true that in metals the charge carriers are electrons. But in other materials like p-type semiconductors or +ions in electrochemical reactions, positive charge carriers predominate. So the engineers, not Benjamin Franklin have developed a convention which defines a positive current as emitting from the positive terminal of a voltage source and returning to the negative terminal
regardless of the polarity of the charge carrier. This is a mathematical artifice that was invented so as to calculate curcuit parameters without regard to charge carrier polarity. If really necessary to know the current direction after the calculations, the direction is reversed if the charge carriers are negative. As you must know, all semiconductor manufacturers and ammeters are marked to show current as if it consisted of positive charge carriers.
Now let's take on Mims' statements. In the first page you submitted, he says that electrons travel at the speed of light. Not true. The electric field that drives them does, but the electrons travel a a much slower rate called the
drift velocity. This is true for electrons in wires or a vacuum tube. The analogy is that of a hose filled with marbles. Push a marble in at one end, and a different marble pops out at the opposite end. After many successive insertions, it takes a long time for the first inserted marble to exit out other end due to its slow drift velocity.
Next he says that electrons are attracted to "holes" caused by positive ions. Well, those positive ions do not possess holes. Those ions are deficient in electrons because a voltage swept them away, as in a capacitor. The electrons are attracted to the positive voltage that caused the ions to form. The difference between the ions in a capacitor and p-type material is that p-type material has a hole built into its ionic struction by dopants, and is electrically neutral. If it were not neutral, there would be a current existing in a slab of p-type material, which there is not. But there is current existing between the plates of an energized capacitor if a conduction path is provided.
On the second page Mim supposedly shows how a diode works, but he doesn't. He only shows how to hook a diode up for forward or reverse bias, not the reason why it works that way.
On the third page is explains current direction by saying Franklin made a mistake. If he labeled a electron as positive, then the holes and ions would be negative. So Franklin was right or wrong no matter which polarity he chose for the electron.
His last paragraph says that the semiconductor labeling was done to accomodate the hole direction. Not true. It was done to be consistent with the mathematical convention of current exiting out the positive terminal of a battery. An ammeter is marked the same way.
Ratch