Diode Current Equation
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PN Junction Diode and its Characteristics
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Application of Zener Diode
LED or Light Emitting Diode
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Tunnel Diode and its Applications
Diode Current Equation
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Amplifier Gain | Decibel or dB Gain
Integrated Circuits | Types of IC
Regulated Power Supply
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Mobility of Charge Carrier
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Electron volt or eV
Energy Quanta | Development of Quantum Physics
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Schrodinger Wave Equation and Wave Function
Cyclotron Basic Construction and Working Principle
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MOS Capacitor | MOS Capacitance C V Curve
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MOSFET as a Switch
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Theory of Semiconductor
Energy Bands of Silicon
Donor and Acceptor Impurities in Semiconductor
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Current Density in Metal and Semiconductor
Intrinsic Silicon and Extrinsic Silicon
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P N Junction Theory Behind P N Junction
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Hall Effect Applications of Hall Effect
Gallium Arsenide Semiconductor
Types of Transistors
Bipolar Junction Transistor or BJT
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Current Components in a Transistor
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DIAC Construction Operation and Applications of DIAC
TRIAC Construction Operation and Applications of TRIAC
Construction of Schottky DiodeAt one ending, there is a junction formed between the metal and lightly doped n-type semiconductor. This is unilateral junction. At the other ending, the metal and heavily doped semiconductor contact is present. It is called Ohmic bilateral contact (see Figure 2 and Figure 3). In this contact, no potential is present and is non-rectifying.
If the doping of semiconductor is increased, the depletion layer width decreases. When the width is decreased to a certain level, the charge carriers will tunnel easily through the depletion region. When the doping is very high, the junction can never act as a rectifier and it will become an ohmic contact. This diode can be a diode and an ohmic contact simultaneously. When a Schottky diode is in unbiased condition, the electrons lying on the semiconductor side have very low energy level when compared to the electrons present in metal. Thus, the electrons cannot flow through the junction barrier which is called Schottky barrier. If the diode is forward biased, electrons present in the N-side gets sufficient energy to cross the junction barrier and enters into the metal. These electrons enter into the metal with tremendous energy. Consequently these electrons are known as hot carrier. Thus the diode is so called as hot-carrier diode. The equivalent circuit of the device (Schottky diode) with typical values of the components is shown below. The above circuit can be approximated as shown below. This approximated circuit is used in many applications. The Schottky diode has some unique features when compared to normal P-N junction diode.
- It is a unipolar device. This is due to the absence of significant current flow from metal to N-type semiconductor (minority carriers in the reverse direction is absent). But P-N junction diode is a bipolar device.
- No stored charge due to the absence of holes in the metal. As a result, schottky diode can quickly switch than other diodes and noise is also relatively low.
- Lower barrier potential (0.2 - 0.25 V) compared to P-N diode (0.7 V)
Comparison of V-I characteristics of Schottky Diode, P-N Junction Diode and Point Contact Diode
Current Components in Schottky DoideThe current condition in this diode is through electrons (majority carriers) in N-type semiconductor. IDiffusion → Diffusion current (result of concentration gradient and diffusion current density of electrons) Dn → Diffusion constant of electrons. q → Electronic charge =1.6 ×1019 C. ITunneling → Tunneling current IThermonic emission → As a result of electron ejection due to thermal energy (thermionic emission), this current will be produced across the electrodes.
Advantages of Schottky DiodeAdvantages of Schottky diode are showing below-
- It has fast recovery time due to very low quantity of stored charge. So this diode is used for high speed switching application.
- It has low turn on voltage.
- It has low junction capacitance.
- Voltage drop is low.
Disadvantages of Schottky DiodeDisadvantages of Schottky diode are showing below-
- Reverse leakage current.
- Low reverse voltage rating.
Application of Schottky Diode
- Used in Switched-mode power supplies.
- Used in reverse current protection.
- Used in discharge protection.
- Used in voltage clamping application.
- Used in RF mixer and Detector diode.
- Used in solar cell application