Crystal diode P-N junction and its unidirectional conductivity 4

b. Apply reverse voltage on both sides of the P-N junction. This refers to the P area being connected to the negative pole of the external power supply, and the N area being connected to the positive pole of the external power supply. This connection is also known as reverse bias, abbreviated as reverse bias,diode as shown in (b) of the figure. As shown in the figure, during reverse polarization, the direction of the external electric field is consistent with that of the internal electric field. The external electric field pulls away the holes and free electrons in the P and N regions on both sides of the space charge region, widening the space charge region and enhancing the internal electric field. This makes it more difficult for the diffusion movement of most charge carriers to occur. In addition,diode  the enhanced internal electric field strengthens the drift motion of minority carriers, and minority carriers in the N and P regions form reverse currents through the P-N junction. Due to the small number of minority carriers, the reverse current is very small, and the P-N junction is in a high resistance state, which is called cutoff. Due to the excitation of minority carriers being temperature dependent, temperature has a significant impact on the reflected current. In summary, the P-N junction is conductive when a forward voltage is applied and non-conductive when a reverse voltage is applied. This characteristic is the unidirectional conductivity of P-N junction, as shown in the following figure.diode