What Is Breakdown Voltage?

The voltage corresponding to the critical breakdown of the PN junction is defined as the breakdown voltage BV of the PN junction. BV is an important parameter for measuring the reliability and range of use of the PN junction. When other performance parameters of the PN junction are unchanged, the value of BV The higher the better.

The voltage corresponding to the critical breakdown of the PN junction is defined as the breakdown voltage BV of the PN junction. BV is an important parameter for measuring the reliability and range of use of the PN junction. When other performance parameters of the PN junction are unchanged, the value of BV The higher the better.

Chinese name

Breakdown voltage

Definition

Dielectric breakdown voltage

Claim

Electric field effect

Alias

Dielectric strength

Overview of breakdown voltage

The voltage at which a dielectric breakdown occurs. A dielectric will lose its dielectric properties and become a conductor under the action of a sufficiently strong electric field, which is called dielectric breakdown, and the corresponding voltage is called breakdown voltage. The electric field strength at the time of dielectric breakdown is called breakdown field strength. Different dielectrics have different breakdown field strengths at the same temperature. When the distance d between the capacitor dielectric and the two plates is constant, it is known from U1-U2 = Ed that the breakdown field strength determines the breakdown voltage. The breakdown field strength is often called the dielectric strength of the dielectric. It is the dielectric strength of the dielectric that plays a key role in improving the withstand voltage of the capacitor. The attached table shows the relative dielectric constant r and dielectric strength of various dielectrics.

Dielectric r breakdown field strength, × 106 / (V · m-1)

The breakdown voltage is the limit voltage of the capacitor. Above this voltage, the dielectric in the capacitor will be broken down. The rated voltage is the voltage that the capacitor can withstand during long-term operation, and it is lower than the breakdown voltage. Capacitors are safe and reliable to work at a voltage not higher than the breakdown voltage. Don't mistake the capacitor for normal operation only at rated voltage.

PN Breakdown mechanism of breakdown voltage PN junction

When the reverse bias of the PN junction is high, electrical breakdown due to impact ionization occurs, that is, avalanche breakdown. The free carriers existing in the semiconductor crystal are accelerated by the built-in electric field in the depletion region, and their energy is continuously increased until they collide with the semiconductor lattice. The energy released during the collision may break the valence bond and generate new electrons Hole pairs. The new electron-hole pairs are accelerated to collide with the lattice, respectively. If the average electron (or hole) can generate more than one electron-hole pair in the process of passing through the depletion region, the process can continue It is strengthened, and eventually the number of carriers in the depletion region increases sharply, and avalanche breakdown of the PN junction occurs. The collision ionization rate is defined as the probability that a carrier will cause a new electron-hole pair through a unit distance in the direction of the electric field. For silicon, the collision ionization rate for electrons and holes is different. To simplify the calculation, We often use the effective value of instead of the respective of holes and electrons, so the critical condition for avalanche breakdown to occur can be expressed as:

It is worth noting that there are some compound semiconductors such as GaAs in which the collision ionization rates of electrons and holes are equal. For these compound semiconductors, formula (1-1) is strictly true. For silicon, the effective value of is about 1.8 × 10E [2]. If the surface junction is considered, the electric field is not a simple one-dimensional distribution. Formula (1-1) is expressed in the form of a vector path integral:

In Equation (1-2), l represents the direction vector of the electric field, which is the position of the depletion region boundary. For example, for a spherical junction, the direction of the electric field is along the radius of the spherical surface, and the carriers are accelerated by the radial electric field until they collide with the lattice or reach the boundary of the depletion region. The critical conditions for avalanche breakdown are:

The voltage corresponding to the critical breakdown of the PN junction is defined as the breakdown voltage BV of the PN junction. BV is an important parameter for measuring the reliability and range of use of the PN junction. With other performance parameters of the PN junction unchanged, we hope that BV The higher the value, the better. Under the condition of one-dimensional electric field distribution, the breakdown voltage can be expressed as:

Considering the non-one-dimensional distribution of the electric field, such as curved or irregular junctions, the more general expression of breakdown voltage is:

The breakdown voltage BV is the integral value of the electric field along the path from its starting point to its ending point.