Electronic Devices PDF

## Electronic Devices (3-Credit) ### 9. Different Types of Materials - **Resistance** and **conductor** - Current cannot flow - Current can flow easily - **Semiconductor** & **Silicon** - Pure Silicon - Semiconductor - Intrinsic - Extrinsic - **Doping** is the pro...

## Electronic Devices (3-Credit) ### 9. Different Types of Materials - **Resistance** and **conductor** - Current cannot flow - Current can flow easily - **Semiconductor** & **Silicon** - Pure Silicon - Semiconductor - Intrinsic - Extrinsic - **Doping** is the process of adding impurities to a semiconductor. ### Semiconductor: - The conductivity of a material is proportional to the concentration of free electrons. - The number of free electrons in a semiconductor lies 107 & 1018 electrons/m². - Semiconductor conductivity is much greater than that of an insulator but much smaller than that of a metal. - Semiconductors typically have a forbidden energy gap of about 1 eV. ### Conductivity of Silicon: - **Intrinsic Silicon**: n = p - **Extrinsic Silicon**: n ≠ p (n-type or p-type) ### Conductivity of Semiconductor: - In a pure semiconductor, the number of holes is equal to the number of electrons. - **Thermal agitation** continues to produce new electron-hole pairs and electrons and holes disappear because of **recombination**. - Each electron-hole pair created has a charge carrying particle: - a **free electron**, negative, with mobility Un - a **hole**, positive, with mobility Up - Electrons and holes move in opposite directions in the field E, but since they have opposite signs, the current due to each is in the same direction. - Therefore, the total current density J within the intrinsic semiconductor is given by: $J= Jn + Jp$ $J= qn \mu n E + qp \mu p E$ - Where: - n → number of electrons per unit volume - p → number of holes per unit volume - E → Applied Electric field strength (V/m) - q → charge of electron or holes in Coulomb - For intrinsic semiconductors: - n = p = ni - Conductivity: $σ = q(ni \mu n + ni \mu p) $ - $σ = qni(\mu n + \mu p)$ - Mobility: $ \mu n$ and $ \mu p$ ### 9. Example - The mobility of free electrons and holes in pure Germanium are 3800 and 1800 cm²/V.s, respectively. - The corresponding values for pure Silicon are 1300 and 500 cm²/V.s, respectively. - Assume ni = 2.5x10¹³ cm^-3 for Germanium and ni = 1.5x10¹⁰ cm^-3 for Silicon at room temperature. - Calculate the intrinsic conductivity for both Germanium and Silicon. **Answer:** **For Germanium** - $\mu n = 3800$ cm²/V.s - $\mu p = 1800$ cm²/V.s - ni = 2.5x10¹³ cm^-3 - $σ = qni(\mu n + \mu p)$ - $σ = q * 2.5 * 10^{13} (3800 + 1800)$ - $σ = q * 1.4 * 10^{17} $ **For Silicon** - $\mu n = 1300$ cm²/V.s - $\mu p = 500$ cm²/V.s - ni = 1.5x10¹⁰ cm^-3 - $σ = qni(\mu n + \mu p)$ - $σ = q * 1.5 * 10^{10} (1300 + 500)$ - $σ = q * 2700 * 10^{10}$ - $σ = q * 2.7 * 10^{14}$ ### Donor and Acceptor Impurities - **Donor impurities**: Pentavalent substances (Antimony, phosphorus, or Arsenic) are added to intrinsic semiconductors. - Four of the impurity atom's five valence electrons form covalent bonds, and the fifth electron is available as a carrier of current. - This impurity is considered an **n-type impurity** and donates excess electron carriers. - **Acceptor impurities**: Trivalent impurities (Boron, Gallium, or Indium) are added to intrinsic semiconductors. - Three covalent bonds are filled, and the vacancy in the fourth band constitutes a **hole**. - This impurity is considered a **p-type impurity** and constitutes a *hole* carrier. ### Energy Band Structure and Conduction in Insulators, Semiconductors, and Conductors - **Insulator**: The energy gap (Eg) between the valence band and conduction band is large (Eg > 6eV). - **Semiconductor**: The energy gap (Eg) between the valence band and conduction band is small (Eg = 1eV). - **Conductor**: The energy gap (Eg) between the valence band and conduction band is zero (Eg = 0 eV). ### Drift and Diffusion - **Diffusion**: The movement of particles because of a concentration gradient. - **PN Junction** - When a P-type semiconductor is joined to an N-type semiconductor, a depletion region is formed at the junction. - **Depletion region**: An area where there are few free charge carriers - **Drift Current**: The flow of electric current due to the motion of charge carriers under the influence of an external electric field. ### PN Junction Diode - **P-N Junction Diode**: Created by joining P-type and N-type semiconductors. - **Forward Bias**: The voltage applied across the diode is such that the p-type terminal is connected to the positive side of the battery and the n-type terminal is connected to the negative side of the battery. - **Reverse Bias**: The voltage applied across the diode is such that the p-type terminal is connected to the negative side of the battery and the n-type terminal is connected to the positive side of the battery. - **Reverse Saturation Current (Io)** : The current that flows through the diode when a reverse bias is applied. - **Forward Current (If)** : the current that flows through the diode when a forward bias is applied. - **Diode Equation**: $Id = Io(e^{\frac{V}{nVT}} - 1)$ - $Id$ → Diode current - $Io$ → Diode reverse saturation current (constant for Ge: 1, Si : 2) - $V$ → Junction thermal voltage - $VT$ → Thermal voltage - **Thermal Voltage**: $VT = \frac{KT}{q}$ - **Boltzmann’s constant**: $K = (1.38066 \times 10^{-23}) J/K$ - **Charge of Electron**: $q = (1.60219 \times 10^{-19}) C$ - **Temperature of the diode junction**: $ \text{ T (in Kelvin)}$ ### Zener Diode - **Zener Diode**: Special kind of diode that is heavily doped. - **Breakdown Voltage**: The reverse voltage at which the diode breaks down and conducts heavily. - **Zener Breakdown**: Occurs at lower reverse voltage due to the creation of a strong electric field across the depletion region. - **Avalanche Breakdown:** Occurs at higher reverse voltage due to the acceleration of charge carriers by the electric field and subsequent collisions with other atoms creating more charge carriers. ### Schottky Diode - **Schottky Diode**: A metal-semiconductor junction diode. - **Schottky Barrier**: The boundary between the metal and semiconductor, which prevents electrons from flowing freely from the semiconductor into the metal. - The Schottky barrier is smaller than a point contact junction. - **Unilateral Device**: Has majority carriers on both sides of the junction, allowing it to switch on and off faster than bipolar transistors. - **Lower forward resistance**: The large contact area between the metal and semiconductor leads to a lower forward resistance and lower noise. ### Solar Cell - **PN Junction**: A p-n junction that acts as photodiode, generating an electric current when exposed to light. - **Solar Cell**: A device that converts light energy into electrical energy. - **Light Energy**: When light falls on the p-n junction, it creates electron-hole pairs. - **Electromagnetic Field**: The electrons and holes move in opposite directions within the electric field, generating a photocurrent. - **External Circuit**: The photocurrent flows through the external circuit and can be used to power devices. ### Bipolar Junction Transistor (BJT) - A **transistor** is a semiconductor device used to amplify or switch electronic signals. - **BJT**: A bipolar junction transistor is a transistor that uses two p-n junctions to control the flow of current. - **NPN transistor**: The emitter is made of n-type semiconductor, the base is made of p-type semiconductor and the collector is made of n-type semiconductor. - **PNP transistor**: The emitter is made of p-type semiconductor, the base is made of n-type semiconductor and the collector is made of p-type semiconductor. - **Emitter**: The region that emits charge carriers. - **Base**: The region that controls the flow of charge carriers from the emitter to the collector. - **Collector**: The region that collects charge carriers. - **Common Emitter configuration**: The base is common to both input and output circuit. - **Common Collector configuration**: The collector is common to both input and output circuit. - **Common Base configuration**: The base is common to both input and output circuit. - **Current Gain**: The ratio of change in output current to the change in input current. ### Field Effect Transistor (FET) - **FET**: A field-effect transistor is a semiconductor device that controls the flow of current through a conducting channel using an electric field. - **JFET**: A junction field-effect transistor, which uses a p-n junction to control the flow of current. - **MOSFET**: A metal-oxide-semiconductor field-effect transistor, which uses a metal gate to control the flow of current. - **N-channel MOSFET**: The semiconductor material is n-type, and the current flows through the channel when the gate is made positive with respect to the source. - **P-channel MOSFET**: The semiconductor material is p-type, and the current flows through the channel when the gate is made negative with respect to the source. <start_of_image> Schematic Diagram of a N-Channel JFET: - Source (S): Connected to the negative pole of the battery. - Drain (D): Connected to the positive pole of the battery. - Gate (G): Connected to the p-type silicon region. - Channel: The n-type silicon region between the source and drain. These pages are a lot about electronic devices and their characteristics, the information is dense. However, by using the markdown formatting and headings, I attempted to create a more structured and readable document from the OCR output.