PN Junction vs Schottky Diode: Key Differences Explained
A PN junction diode rectifies with a junction between p-type and n-type semiconductors, while a Schottky diode rectifies with a junction between a metal and a semiconductor. In a PN junction, minority carriers are injected and stored under forward bias, so a reverse recovery current flows when the diode is switched to reverse bias. A Schottky diode runs on majority carriers only, so it has almost no reverse recovery, and in silicon its forward voltage of about 0.2 to 0.4 V is also lower than the roughly 0.6 to 0.7 V of a PN junction. The trade-off is a larger reverse leakage current and, in silicon, difficulty reaching high breakdown voltages.
| Aspect | PN junction diode | Schottky diode |
|---|---|---|
| Structure | A junction of p-type and n-type semiconductors | A junction of a metal and a semiconductor (mainly n-type), called a Schottky junction |
| Current carriers | Injected minority carriers. Both electrons and holes are involved | Majority carriers only. Current flows by thermionic emission over the barrier |
| Forward voltage (silicon, typical) | About 0.6 to 0.7 V | About 0.2 to 0.4 V. Depends on the metal and the voltage rating |
| Reverse recovery | Yes. Reverse current flows until the stored minority carriers disappear. On the order of µs for general-purpose rectifiers and about tens of ns for fast-recovery parts | Almost none. The only current is the one that charges and discharges the junction capacitance |
| Reverse leakage current | Small | Large. The lower the barrier, the larger the leakage |
| Breakdown voltage (silicon, typical) | High voltage ratings are easy to make, up to the several-kV class | Up to about 200 V. In SiC, 600 to 1700 V class parts are in practical use |
| Voltage drop at high current in high-voltage parts | Conductivity modulation lowers the resistance of the lightly doped layer, keeping the voltage drop down | No conductivity modulation, so the drift-layer resistance adds directly |
| Temperature behavior | Forward voltage falls by about −2 mV/°C. Leakage current rises with temperature | Leakage current rises sharply with temperature, so thermal runaway must be watched. Forward voltage falls with temperature |
| Main uses | Rectifying mains power, high-voltage rectification, general-purpose protection and signal circuits | Low-voltage, high-current rectification in switching power supplies, freewheeling diodes, reverse-polarity protection, high-frequency detection |
Figures are typical orders of magnitude and vary by process generation and product.