Crystal diode P-N junction and its unidirectional conductivity 3

The positive and negative ions that form a space charge region are also known as space charges. Although they are all charged, they cannot move and do not participate in conduction. And most of the charge carriers in the space charge region have diffused to each other and recombined, so there are very few charge carriers in the space charge region, resulting in a high resistivity of the space charge region. The above discussion is about the situation where there is no external voltage applied to the P-N junction. ② The potential barrier of P-N junction. Due to the formation of an electric field within the space charge region, there is a region called a potential barrier or potential barrier that hinders the passage of charge carriers through the P-N junction, as shown in the following figure.diode

③ Unidirectional conductivity of P-N junction. The state of charge distribution (generating an electric field) refers to the electric charge. The potential barrier of the P-N junction under the potential potential state (potential barrier) diagram. a. Apply a forward voltage on both sides of the P-N junction. This refers to the P area being connected to the positive pole of the external power supply, and the N area being connected to the negative pole of the external power supply. This connection is also known as forward bias, abbreviated as positive bias, as shown in Figure (a) above. As shown in the figure, the direction of the external electric field is opposite to that of the internal electric field when biased forward. When the forward voltage is large enough,diode  the external electric field drives the majority of charge carriers in the P and N regions into the space charge region, where they separate from the negative and positive space charges in the space charge region, narrowing the space charge region and weakening the internal electric field. This is conducive to the strengthening of diffusion motion, so that most charge carriers smoothly pass through the P-N junction, forming a larger forward current. The forward current includes two parts: hole current and electron current. The polarity of the charge carriers in the two parts is different, and their movement directions are opposite, but the direction of the current is the same. Within a certain range, the higher the applied forward voltage, the greater the forward current. When the forward current reaches a certain value, the P-N junction enters a low resistance state, which is called conduction.diode