1. Faculty of Degree Engineering - 083 Department of Electronic& communication Engineering - 11 Subject: EDC (2131006) Topic: Schottky Diode Prepared By: Hardik Thumar (140830111005) Kundan Vaghela (140830111006) Guided By: Prof. N.Y.Chavda

2. SCHOTTKY BARRIER DIODE The Schottky diode (named after German physicist Walter H. Schottky; also known as hot carrier diode) is a semiconductor diode with a low forward voltage drop and a very fast switching action. When current flows through a diode there is a small voltage drop across the diode terminals. A normal silicon diode has a voltage drop between 0.6–1.7 volts, while a Schottky diode voltage drop is between approximately 0.15–0.45 volts. This lower voltage drop can provide higher switching speed and better system efficiency.

3. CONSTRUCTION A metal–semiconductor junction is formed between a metal and a semiconductor, creating a Schottky barrier (instead of a semiconductor– semiconductor junction as in conventional diodes). Typical metals used are molybdenum, platinum, chromium or tungsten; and the semiconductor would typically be N-type silicon. The metal side acts as the anode and N-type semiconductor acts as the cathode of the diode. This Schottky barrier results in both very fast switching and low forward voltage drop.

4. Reverse recovery time The most important difference between the p-n and Schottky diode is reverse recovery time, when the diode switches from conducting to non-conducting state. Where in a p-n diode the reverse recovery time can be in the order of hundreds of nanoseconds and less than 100 ns for fast diodes, Schottky diodes do not have a recovery time, as there is nothing to recover from (i.e. no charge carrier depletion region at the junction).

5. CONSTRUCTION AND APPLICATIONS It is often said that the Schottky diode is a "majority carrier" semiconductor device. This means that if the semiconductor body is doped n-type, only the n-type carriers (mobile electrons) play a significant role in normal operation of the device. The majority carriers are quickly injected into the conduction band of the metal contact on the other side of the diode to become free moving electrons. Therefore no slow, random recombination of n- and p- type carriers is involved, so that this diode can cease conduction faster than an ordinary p-n rectifier diode. This property in turn allows a smaller device area, which also makes for a faster transition.majority carrierdopedelectronsfree moving electronsrecombinationdiode

6. This is another reason why Schottky diodes are useful in switch-mode power converters; the high speed of the diode means that the circuit can operate at frequencies in the range 200 kHz to 2 MHz, allowing the use of small inductors and capacitors with greater efficiency than would be possible with other diode types. Small-area Schottky diodes are the heart of RF detectors and mixers, which often operate up to 50 GHz.

7. Limitations The most evident limitations of Schottky diodes are the relatively low reverse voltage ratings for silicon-metal Schottky diodes, typically 50 V and below, and a relatively high reverse leakage current. Some higher- voltage designs are available; 200V is considered a high reverse voltage.

8. *Other Two-Terminal Devices *Schottky Barrier Diodes

9. Two-Terminal Devices Having A Single p-n Junction  Schottky  Tunnel  Varactor  Photodiode  Solar Cell

10. Other Two-Terminal Devices Of A Different Construction  Photoconductive Cell  LCD (Liquid-Crystal Display)  Thermistor

11. Schottky-Barrier Diode *Surface-Barrier/Hot-Carrier Diode

12. Schottky Diode Areas of Application  Very high frequency range  Lower noise figure  Low-voltage or high-current power supplies  AC-to-DC converters  Radar systems  Schottky TTL logic

13. Schottky/ hot-carrier diode Gold leaf metal contact Anode (+) Metal Silicon dioxide screen Metal semiconductor junction Metal contact Cathode (-)

14. Comparison of characteristics of hot- carrier and p-n junction diodes IDID VDVD p-n junction diode Hot carrier diode Hot carrier diode p-n junction diode

15. Fig. 20.5 Motorola Schottky barrier devices. (Courtesy Motorola Semiconductor Products, Incorporated I O Average rectified forward current (amperes) V RRM (Volts) Case Anode Cathode 51-02 (DO-7) Glass 59-04 Plastic 267 Plastic 60 Metal 257 (DO-4) Metal 257 (DO-5) Metal 430-2 (DO-21) Metal 20 MBR020 IN5817 MBR120P IN5820 MBR320P MBR320M IN5823IN5826 MBR1520 IN5829 MBR2520 IN5832 MBR4020 MBR4020PF 30 MBR030 IN5818 MBR130P IN5821 MBR330P MBR330M IN5824IN5827 MBR1530 IN5830 MBR2530 IN5833 MBR4030 MBR4030PF 35 MBR135PMBR335P MBR335M MBR1535MBR2535MBR4035 MBR4035PF 40 IN5819 MBR140P IN5822 MBR340P MBR340M IN5825IN5828 MBR1540 IN5831 MBR2534 IN5834 MBR4040 I FSM (Amps) 5.010050250200500 800 T C @ Rated I O ( º C) 85808580757050 T J Max125ºC Max V F @ I FM = I O

16. I-V characteristics Where I s = Saturation current q = charge, V A is applied voltage, k = boltzman constant, and T= Temperature. The reverse leakage current for a Schottky diode is generally much larger than that for a p + n diode.