Crystal diode P-N junction and its unidirectional conductivity 2

Two ions with different charged properties in the space charge region can establish an internal electric field within the space charge region. Obviously, the direction of the internal electric field is from the positively charged N region to the negatively charged P region. diode As the diffusion motion progresses, the internal electric field continuously strengthens, and the diffusion motion weakens with the strengthening of the internal electric field, because the internal resistance blocks the diffusion of most charge carriers. On the contrary, the internal electric field drives the movement of minority carriers, causing them to enter the opposite region separately. diode The regular movement of minority charge carriers under the influence of an internal electric field is called drift motion. Diffusion and drift move in opposite directions. With the weakening of diffusion motion and the strengthening of drift motion, a dynamic equilibrium state will inevitably be reached in the end. So, the width of the space charge region is fixed. The current flowing through the space charge region includes diffusion current (also known as forward current) formed by the diffusion motion of majority carriers, and drift current (also known as reverse current) formed by the drift motion of minority carriers. The net current that instantly flows through the cross-section of the space charge region is the algebraic sum of the forward and reverse currents. When diffusion and drift reach dynamic equilibrium, the net current is zero. The P-N junction is actually a state where the net current is zero.diode