1-3-2. Reverse biasing

A reverse bias of V_R causes the diffusion potential to increase by V_R. Although electrons are the majority carriers in the n-type semiconductor and the minority carriers in the p-type semiconductor, the electron density of the p-type semiconductor becomes higher than that of the n-type semiconductor above the diffusion barrier, V_D + V_R (as opposed to the unbiased and forward-biased states). As a result, electrons, the minority carriers in the p-type semiconductor, diffuse into the n-type semiconductor. The amount of minority carrier diffusion that occurs under reverse bias is much smaller than that that occurs under forward bias. However, under reverse bias, electrons are injected into the p-type semiconductor to compensate for the diffusion while holes are injected into (i.e., electrons are drawn away from) the n-type semiconductor. Therefore, under reverse bias, current flows in the direction opposite to the one under forward bias. The reverse current is very low as it is due to minority carrier diffusion.