Energy Quanta | Development of Quantum Physics
Wave Particle Duality Principle
Schrodinger Wave Equation and Wave Function
Heisenberg Uncertainty Principle
Electron volt or eV
Theory of Semiconductor
Mobility of Charge Carrier
Energy Bands of Silicon
Intrinsic Silicon and Extrinsic Silicon
Current Density in Metal and Semiconductor
Conductivity of Semiconductor
What are photo electrons?
Donor and Acceptor Impurities in Semiconductor
Diode | Working Principle and Types of Diode
p-n Junction Diode and Characteristics of p-n Junction
Half Wave Diode Rectifier
Full Wave Diode Rectifier
P-I-N Photodiode | Avalanche Photo Diode
Tunnel Diode and its Applications
LED or Light Emitting Diode
Light Dependent Resistor | LDR and Working Principle of LDR
Zener Diode | Symbol and Application as Voltage Regulator
Laser | Types and Components of Laser
Applications of Bipolar Junction Transistor or BJT | History of BJT
Biasing of Bipolar Junction Transistor | BJT or Bipolar Transistor Biasing
Bipolar Junction Transistor or BJT | N-P-N or P-N-P Transistor Application Theory Biasing Amplifier
MOSFET | Working Principle of p-channel n-channel MOSFET
MOS Capacitor | MOS Capacitance C V Curve
JFET or Junction Field Effect Transistor
Integrated Circuits | Types of IC
Op-amp | Working Principle of Op-amp
Amplifier Gain | Decibel or dB Gain
Regulated Power Supply
p-n Junction Diode and Characteristics of p-n Junctionintrinsic semiconductor is doped with acceptor i.e, one side is made p-type by doping with n-type material, a p-n junction diode is formed. This is a two terminal device. It appeared in 1950’s.
P-N junction can be step graded or linearly graded. In step graded the concentration of dopants both, in n - side and in p - side are constant up to the junction. But in linearly graded junction, the doping concentration varies almost linearly with the distance from the junction. When the P-N diode is in unbiased condition that is no voltage is applied across it, electrons will defuse through the junction to p - side and holes will defuse through the junction to n - side and they combine with each other. Thus the acceptor atom near the p - side and donor atom near n – side are left unutilized. An electron field is generated by these uncovered charges. This opposes further diffusion of carriers. So, no movement of region is known as space charge or depletion region. If, we apply forwards bias to the p-n junction diode. That means if positive side of the battery is connected to the p – side, then the depletion regions width decreases and carriers flow across the junction. If the bias is reversed the depletion width increases and no charge can flow across the junction.
P-N Junction Diode CharacteristicsLet's a voltage V is applied across a p-n junction and total current I, flows through the junction. It is given as. I = IS[exp(eV/ɳKBT) - 1] Here, IS = reverse saturation current e = charge of electron ɳ = emission co-efficient KB = Boltzmann constant T = temperature The current voltage characteristics plot is given below. The current voltage characteristics When V is positive the junction is forward biased and when V is negative, the junction is reversing biased. When V is negative and less than VTH, the current is very small. But when V exceeds VTH, the current suddenly becomes very high. The voltage VTH is known as threshold or cut in voltage. For Silicon diode VTH = 0.6 V.
At a reverse voltage corresponding to the point P, there is abrupt increment in reverse current. The PQ portion of the characteristics is known as breakdown region.
P-N Junction Band DiagramFor an n-type semiconductor, the Fermi level EF lies near the conduction band edge. EC but for an p - type semiconductor, EF lies near the valance band edge EV Now, when a p-n junction is built, the Fermi energy EF attains a constant value. In this scenario the p-sides conduction band edge. Similarly n–side valance band edge will be at higher level than Ecn, n-sides conduction band edge of p - side. This energy difference is known as barrier energy. The barrier energy is EB = Ecp - Ecn = Evp - Evn If we apply forward bias voltage V, across junction then the barrier energy decreases by an amount of eV and if V is reverse bias is applied the barrier energy increases by eV.
P-N Junction Diode EquationThe p-n junction diode equation for an ideal diode is given below
I = IS[exp(eV/KBT) - 1]
Here, IS = reverse saturation current e = charge of electron KB = Boltzmann constant T = temperature
For a normal p-n junction diode, the equation becomes
I = IS[exp(eV/ɳKBT) - 1]
Here, ɳ = emission co-efficient, which is a number between 1 and 2, which typically increases as the current increases.