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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 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 • A metal–semiconductor junction is formed CONSTRUCTION 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. 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). • CONSTRUCTION AND It is often said that the Schottky diode is a "majorityAPPLICATIONS 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 • 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. 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 highervoltage designs are available; 200V is considered a high reverse voltage. *Other Two-Terminal Devices *Schottky Barrier Diodes Two-Terminal Devices Having A Single p-n Junction Schottky Tunnel Varactor Photodiode Solar Cell Other Two-Terminal Devices Of A Different Construction Photoconductive Cell LCD (Liquid-Crystal Display) Thermistor Schottky-Barrier Diode *Surface-Barrier/Hot-Carrier Diode 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 Schottky/ hot-carrier diode Gold leaf metal contact Anode (+) Metal Silicon dioxide screen Metal semiconductor junction Metal contact Cathode (-) Comparison of characteristics of hotcarrier and p-n junction diodes ID Hot carrier diode p-n junction diode VD p-n junction diode Hot carrier diode Fig. 20.5 Motorola Schottky barrier devices. (Courtesy Motorola Semiconductor Products, Incorporated IO Average rectified forward current (amperes) VRRM (Volts) Case Anode Cathode 59-04 Plastic MBR4040 800 430-2 (DO-21) Metal MBR4030 IN5833 MBR2530 IN5830 MBR1530 IN5827 IN5824 IN5821 MBR4035 MBR2535 MBR1535 MBR335M MBR335P MBR135P MBR4020PF MBR4030PF MBR4035PF IN5834 800 MBR4020 MBR2534 800 IN5832 IN5831 800 MBR2520 MBR1540 500 IN5829 IN5828 500 MBR1520 IN5825 500 IN5826 MBR340M 500 IN5823 MBR340P 200 MBR330M IN5822 MBR320M MBR140P 250 MBR330P MBR130P IN5819 Max VF @ IFM = IO MBR320P MBR120P IN5818 50 IN5820 IN5817 TJ Max 257 (DO-5) Metal 100 40 TC @ Rated IO (ºC) 257 (DO-4) Metal 60 Metal 5.0 35 IFSM (Amps) 267 Plastic MBR030 30 MBR020 20 51-02 (DO-7) Glass 800 85 80 85 80 75 70 50 125ºC I-V characteristics I I s e qVA kT 1 Where Is = Saturation current q = charge , VA 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.