For example, minority carrier lifetime control technology. Because the change of minority carrier lifetime and the control method of minority carrier lifetime affect the frequency characteristics and reverse recovery softness of fast recovery devices, the control technology of minority carrier lifetime is very important. The minority carrier lifetime control technology can be divided into three types according to its characteristics: conventional type, heavy metal doping type and electron radiation type.

1) Conventional type: Conventional type is to control minority carrier lifetime by adjusting the structure parameters of switch tube, including several methods: reducing material resistivity, controlling impurity distribution, and thinning base thickness.

2. Heavy metal doping: In the process of diode manufacturing, consciously choose a suitable deep level heavy metal impurity to diffuse in semiconductor, which can be used to reduce minority carrier lifetime and improve reverse recovery softness. Commonly used heavy metal impurities are gold, platinum, palladium and so on.

3) Electron radiation type: Its characteristic is that the minority carrier lifetime can be accurately controlled by adjusting the dose of electron injection, so that the different requirements of minority carrier lifetime for various electrical parameters of devices can be well coordinated, and it can be carried out after the device is manufactured, making the manufacturing process simple and flexible.

3: New structure

New structures are used to improve the performance of the diodes, such as ideal ohmic contacts. The traditional PIN rectifier uses ohmic contact at the N-N + interface only for multi-sub. Ohmic contact structure is not formed for minority n-n+due to the influence of built-in electric field produced by n-n+high and low junctions. Ideal ohmic contact is an interface that allows both minority and poly to pass smoothly. It is composed of P + region and N + region embedded in each other. In this structure, the hole passes through the interface and the electron passes through the interface. The structure can be obtained by the traditional selective diffusion method or by using Schottky contact instead of the whole p + region, thus eliminating the one-time selective diffusion process.

Recently, amorphous silicon, germanium and boron alloys with high conductivity are deposited on p-type silicon wafers by CVD method as ideal contact layer in the process of making diodes, which makes the diodes have low consumption rectification characteristics in positive bias and fast switching characteristics in bias. The reverse recovery time of the diode with ideal ohmic contact is up to 60 ns, and the leakage current is lower, so that the diode can work at high temperature.

The traditional method of fabricating fast diodes is to reduce minority carrier lifetime by doping gold, platinum or electron irradiation. However, due to the mutual constraints of parameters such as reverse recovery time, reverse peak current, attenuation speed and forward voltage drop, this device has been used in many power electronics applications. Therefore, it is particularly important to fabricate a high-speed diode with short reverse recovery time, low reverse peak current and soft recovery characteristics. For this purpose, different structures of these diodes have been developed, such as concave step "cathode short circuit" structure with auxiliary diodes, cathode short circuit structure, self-tuning emission efficiency and ideal ohmic contact diode (SIOD).