Schottky diode principle
Schottky diode is precious metal (gold, silver, aluminum, platinum, etc.) A is positive to n-type semiconductor B for negative, the use of the contact surface formation of barrier has rectifier characteristics and are made of - semiconductor devices. Because n-type semiconductor there are A large number of electronic, precious metals in only A minimum amount of free electrons, so the electronic and high concentration from B to lean A diffusion. Obviously, A metal no hole, also does not exist hole from A to B's diffusion motion. Along with the electronic constantly from B spread to A, B surface electron concentration surface gradually drop light industry ministry, the surface electric neutral be destroyed, then form barrier, its electric field direction for B - A. But in this field under the role, A in the electronic also can produce from A to B drift motion, thus extinction the diffusion motion and the formation of electric field. When set up certain width of the space charge region, electric field caused by electronic drift movement and concentration caused by different electronic diffusion motion relative to the balance, formed schottky barrier.
The typical schottky rectifier internal circuit structure is n-type semiconductor as substrate, the above form with arsenic as dopant of N - epitaxial layer. Anode (resistance file layer) metal material is molybdenum. Silica (SiO2) is used to eliminate the edge area electric field, and improve the pipe pressure value. N type substrate has very little on state resistance, the doping concentration is H - layer to high 100% times. In the substrate under formation N + cathode layer, its function is to reduce the cathode contact resistance. By adjusting the structure parameters, can be in substrate and anode metal formed between the right schottky barrier, when combined with positive bias E, metal A and N type substrate B power connection of positive, negative, the barrier width Wo narrowing. Plus negative bias - E, barrier width will increase.
To sum up, schottky rectifier tube structure principle and PN junction rectifier has the very big difference will usually be p-n junction rectifier tube called "rectifier tube, and the metal - half catheter rectifier is called a schottky rectifier tube, in recent years, using silicon plane manufacture process of aluminum silicon schottky diode has also come out, this can not only save precious metals, reduce cost, but also improve the consistency of the parameters.
Schottky rectifier tube in only one kind of carrier (electronic) delivery charge, in barrier lateral there is no excess minority carrier accumulation, therefore, there is no charge storage problem (Qrr - 0), make the switch characteristic for show improvement. The reverse recovery time already can shorten to less than 10 ns. But its reverse pressure value is low, usually not more than to 100 v. Therefore appropriate in the low pressure, large current work. Use its low pressure drop this characteristic, can improve the low pressure, large current rectifier (or fly-wheel) circuit efficiency.
