Hole flow

In a P-type semiconductor, most of the current flows in a way that some people find peculiar and esoteric. In a literal sense, in virtually all electronic devices, charge transfer is always the result of electron movement, no matter what the medium might be. The exceptions are particle accelerators and cloud chambers—apparatus of interest mainly to theoretical physicists.
The flow of current in a P-type material is better imagined as a flow of electron absences, not electrons. The behavior of P-type substances can be explained more easily this way. The absences, called “holes,” move in a direction opposite that of the electrons. Imagine a sold-out baseball stadium. Suppose 19 of every 20 people are randomly issued candles. Imagine it’s nighttime, and the field lights are switched off. You stand at the center of the field, just behind second base.The candles are lit, and the people pass them around the stands. Each person having a candle passes it to the person on their right if, but only if, that person has no candle. You see moving dark spots: people without candles. The dark spots move against the candle movement. The physical image you see is produced by candle light, but the motion you notice is that of candles absences.
Figure 1 illustrates this phenomenon. Small dots represent candles or electrons. Imagine them moving from right to left in the figure as they are passed from person to person or from atom to atom. Circles represent candle absences or holes. They “move” from left to right, contrary to the flow of the candles or the electrons, because the candles or electrons are being passed among stationary units (people or atoms). This is just the way holes flow in a semiconductor material.

Figure 1: Pictorial representation of hole flow. Small dots represent electrons, moving one way; open circles represent holes, moving the other way.