The majority carriers(electrons) of the n-type material must overcome the attractive forces of the layer of positive ions in the n-type material and the shield of negative ions in the p-type material to migrate into the area beyond the depletion region of the p-type mate- rial. However, the number of majority carriers is so large in the n-type material that there will invariably be a small number of majority carriers with kinetic energy to pass through the depletion region into the p-type material. Again, the same type of discussion can be applied to the majority carriers(holes) of the p-type material The resulting flow due to the majority carriers is shown at the bottom of Fig. 1.12c. A close examination of Fig. 1.12c will reveal that the relative magnitudes of the flow vectors are such that the net flow in either direction is zero. This cancellation of for each type of carrier flow is indicated by the crossed lines. The length of the vector representing hole flow is drawn longer than that of electron flow to demonstrate that the two magnitudes need not be the same for cancellation and that the doping levels for each material may result in an unequal carrier flow of holes and electrons. In summary therefore In the absence of applied bias across a semiconductor diode, the net flow of charge an in one direction is zero. In other words, the current under no-bias conditions is zero, as shown in Figs. 1.12a and 1.12b