The structural characteristics of fast recovery and ultra fast recovery diodes

What are the structural characteristics of fast recovery diodes and ultrafast recovery diodes? What's the difference between them?
The internal structure of a fast recovery diode is different from that of a regular diode, as it adds a base region I between P-type and N-type silicon materials to form a P-I-N silicon wafer. Due to the thin base region, the reverse recovery charge is very small, which not only greatly reduces the TRR value, but also reduces the transient forward voltage drop, allowing the diode to withstand high reverse operating voltages. The reverse recovery time of a fast recovery diode is generally several hundred nanoseconds, the forward voltage drop is about 0.6V, the forward current is several amperes to several thousand amperes, and the peak reverse voltage can reach several hundred to several thousand volts. The reverse recovery charge of the ultrafast recovery diode is further reduced, allowing its TRR to be as low as tens of nanoseconds.

Fast recovery and ultra fast recovery diodes below 20A are mostly packaged in TO-220. From the perspective of internal structure, it can be divided into two types: single diode and double diode (also known as double diode). There are two fast recovery diodes inside the diode, which can be divided into common cathode pair and common anode pair according to the different connection methods of the two diodes. Figure 2 (a) shows the external and internal structure of the C20-04 fast recovery diode (single diode). (b) The figure and figure (c) show the appearance and structure of C92-02 type (common cathode pair) and MUR1680A type (common anode pair) ultrafast recovery diodes, respectively. They are all packaged in TO-220 plastic, and fast recovery diodes with tens of amps are generally packaged in TO-3P metal shells. Pipes with larger capacities (several hundred to several thousand amperes) are packaged in bolt or flat form.