Avalanche Photodiode. Introduction When measuring low light levels, a vacuum tube photomultiplier tube or some form of solid-state detector which relies on multiplication (e.g. Zener Breakdown This type of break-down appears in the high doping diode like Zener, as this diode has less depletion area due to higher doping. Found inside – Page 2-62Paradoxically , the Zener breakdown occurs at lower voltages and the Avalanche breakdown occurs at higher voltages . Breakdown diodes are designed for a ... In this case, an avalanche diode is used as the direct feedback. Zener Diode Explanation. The avalanche diode is constructed in a way similar to that of the Zener diode, and both Avalanche breakdown, as well as Zener breakdown, are present in an avalanche diode. Here, you can see the symbol of Avalanche Diode. This diode junction is mainly designed for avoiding the concentration of current so the diode will not damage with the breakdown. The threshold voltage above which the circuit disconnects the supply to the load side is called the circuit's pre-set voltage value. STUD 1 Fuse l 40A Trailer Wiring / Automatio Level Control Compressor ABS Fuse 52 6OA Brake Pressure Modulator Valve (PumP) IGN A Fuse #3 40A Starter Relay, Ignition Switch IGN 1. When wired in reverse (when collector and emitter are reversed) Each of the plurality of pulling circuits is arranged . A pin photodiode consists of three regions. Avalanche breakdown is a phenomenon observed in a p-n junction diode in reverse bias. Aside: The actual physics of what happens at breakdown is quite interesting; two separate effects, the Zener effect and Avalanche breakdown both contribute to this behavior. The avalanche diode is constructed in a way similar to that of the Zener diode, and both Avalanche breakdown, as well as Zener breakdown, are present in an avalanche diode. Diodesare essentially switches that allow current to easily flow in one direction while resisting current flowing in the opposite direction. TURN. Avalanche diodes are specially designed for avalanche breakdown and they experience a voltage drop because of the breakdown conditions. The Avalanche Diode is supposed to be in reverse bias. In standard diodes, Tachometer Wire Location: At ECM. The main difference of the avalanche photodiode to other forms of photodiode is that it operates under a high reverse bias condition. Found inside – Page 1Avalanche - Diode Oscillator SHING - GONG LIU , MEMBER , IEEE T : Abstract - A simple microstrip oscillator circuit has been designed microstrip circuit . The study of photonics has one underlining challenge: detecting a single photon. Found inside – Page 2-62Paradoxically, the Zener breakdown occurs at lower voltages and the Avalanche breakdown occurs at higher voltages. Breakdown diodes are designed for a ... Avalanche Diode. The image sensor includes a plurality of pixel circuits arranged in a matrix, a plurality of pulling circuits and a global current source circuit. This book presents an overview of new optical communication technologies and a bird's-eye view of some of the more promising technologies among them. Avalanche Diode. The diagram shows the basic principle: While the voltage is rising the diode … velocity of minority carrier increases as they diffuse across the junction.As the reverse bias is . 2004 Chevrolet Avalanche Relay Block. Found inside – Page 2-69Explain the operation of a current source using FETs with a neat diagram. ... Explain a voltage reference circuit using Avalanche diode reference 2.39 2.40 ... Due to avalanche breakdown, a conventional diode is subject to high current when the reverse bias breakdown voltage is exceeded. The initial avalanche current is concentrated mainly in the diode localized in the deep zone The purpose of the avalanche photodiode is to provide an initial amplification of photo current within the diode itself. It is a small device with disproportional characteristics whose applications are … It is like P-N photodiode or PIN photodiode where electron-hole pairs are generated due to absorption of photons but in addition to this avalanche photodiode uses the impact ionisation principle for . Found inside – Page 237336 Avalanche photodiode: (A) structure, (B) energy band diagram, ... If a load is connected to the diode, a current will conduct in the circuit. Avalanche diodes are utilized as support valves to control the pressure of the system to save . Avalanche diode is another diode which has the similar characteristics of Zener diode. Ⅱ Main Features of Avalanche Photodiode (1) Avalanche gain coefficient M (also called multiplication factor), the main characteristics of abrupt junction avalanche diodes In the formula, V is a reverse bias voltage, and VB is a body avalanche breakdown voltage; n is a constant with respect to a material, a device structure, and an incident wavelength, and has a value of 1 to 3. The positive terminal of the battery is connected to the anode side of the diode. . It is this feature which gives rise to the name "Single Photon Avalanche Diode." Forward-Biased Safe Operating Area (FBSOA) Capability Found inside – Page 94In early studies on silicon avalanche diodes in Geiger mode the simple passive quenching circuit (PQC) outlined in Fig. 4.7a was used. An imaging device may include a plurality of single-photon avalanche diode (SPAD) pixels. The avalanche breakdown occurs when a high reverse voltage is applied across the diode. This article discusses about a brief information about the construction and working of an avalanche diode. Jump to navigation Jump to search. An electron avalanche is a process in which a number of free electrons in a transmission medium are subjected to strong acceleration by an electric field and subsequently collide with other atoms of the medium, thereby ionizing them (impact ionization). This diode junction is mainly designed for avoiding the concentration of current so the diode will not damage with the breakdown. An avalanche diode structure similar to that of a Schottky photodiode may also be used but the use of this version is much less common. Avalanche Breakdown Voltage. Avalanche diode. Figure 6: Avalanche Breakdown. It allows multiplication of an Avalanche Breakdown to each photo-produced electron-hole pair. The diagram only shows highly energetic holes creating electron-hole pairs. This can mean that the diode is operating close to the reverse breakdown area of its characteristics. Each of the plurality of pixel circuits includes a single photon avalanche diode and four P-type or N-type transistors. With built-in avalanche diode. Avalanche diode, Geiger avalanche diode, silicon photomultiplier) is normally used. In this module on pn junction under bias, we will cover the following topics: Energy band diagram of pn junction under bias, Capacitance-voltage characteristics, Impact ionization, Avalanche breakdown, Avalanche breakdown voltages, Tunneling current, Zener breakdown, Energy band diagram of pn junction under forward bias, Continuity equation, Boundary conditions, Ideal diode equation, Long- and . What is Avalanche Diode? Found inside – Page 252Zener, Avalanche, and Tunnel (Esaki) Diodes In the breakdown region in the ... Zener diodes Vext I I I I I O O FIGURE 4.43 Band diagram for Zener diode: the ... The construction of avalanche diode is similar to zener diode but the doping level in avalanche diode differs from zener diode. Photodiode Photodiode working principle: It is a semiconductor device commonly known as PIN photodiode consists of an active p-n junction which operates in reverse bias. V-I Characteristics of a Zener diode. The construction of the avalanche diode is similar to the Zener diode, and indeed both Zener breakdown and Avalanche breakdown are present in these diodes. Schematic Diagram Of An Avalanche Photodiode Ilrating The Scientific Found inside – Page 98Gibbons , G. , Avalanche Diode Microwave Oscillates , Clarendon Press , Oxford ... front in the depletion layer of a TRAPATT diode with necessary diagrams . The passage of current at those points where avalanche initially occurs is … Schematic diagram of an avalanche apd receiver photodiode array for noise diode construction working reverse depletion mechanism structure geiger photodiodes g apds detector circuit pin single photon detection using in optical fiber. The integral diode of a MOSFET is the collector-base junction of the parasitic transistor. The avalanche breakdown takes place across the entire PN junction, when the voltage drop is constant and is independent of current. SCHOTTKY DIODE. Found inside – Page 2724.34 Schematic diagram of the avalanche diode. ac > 07h; but in III—V material, GaAs and InP and others they are almost equal. The collisional increase in ... This type of break-down not only exits in the Zener diode but also in the general diode due to higher voltage in reversed biased conditions. Found inside – Page 255Explain the constructional features of avalanche diodes. 4. ... Explain with a suitable circuit diagram the working of a Zener voltage regulator. 7. Avalanche Photodiode. Avalanche Diode. A Zener Diode, also known as a breakdown diode, is a heavily doped semiconductor device that is designed to operate in the reverse direction. In this case, an avalanche diode is used as the direct feedback. Forward … This article discusses about a brief information about the construction and working of an avalanche diode. Therefore, the width of depletion region in zener diode is very thin. Avalanche diode What is avalanche diode? Avalanche Diodes are those which work in avalanche breakdown mode without damaging themselves. This enables avalanche multiplication of the holes and electrons created by . Share. Principles of Operation A high field avalanche zone propagates through the diode and fills the depletion layer with a dense plasma of electrons and holes that. In this breakdown, when the electric field is applied across the diode, the velocity of the charge carrier increases. In this breakdown, when the electric field is applied across the diode, the velocity of the charge carrier increases. A single-photon avalanche diode (SPAD) is a class of photodetectors that can detect low-intensity signals down to a single photon. This is called the 'Avalanche' breakdown. Avalanche photodiodes are named that for a reason: The term avalanche refers to the internal APD gain – the so-called avalanche breakdown. Avalanche breakdown. Found inside – Page 2424.2.1 Advanced p-i-n and Avalanche Photodiodes Although the working principles ... Schematic diagram of a p-i-n photodiode The schematic diagram of a p-i-n ... Another disadvantage is the chances of avalanche breakdown of the Zener diode. Zener diodes are heavily doped. In electronics, an avalanche diode is a diode (made from silicon or other semiconductor) that is designed to experience avalanche breakdown at a specified reverse bias voltage. Found inside – Page 56-10Due to the internal multiplication factor M, an avalanche photodiode is much more sensitive than a PIN diode. The sensitivity of a receiver equipped with an ... Found inside – Page 87Upconverted noise We have previously noted that the avalanche diode is a highly non ... The circuit impedance is a function of frequency only , whereas the ... On detecting an incident photon, the SPAD output a voltage pulse generated by an avalanche breakdown current and a quenching resistor. • The concept of diodes is easy to understand with the help of the illustrations below. Ⅰ Definition of Avalanche Photodiode. In this module on pn junction under bias, we will cover the following topics: Energy band diagram of pn junction under bias, Capacitance-voltage characteristics, Impact ionization, Avalanche breakdown, Avalanche breakdown voltages, Tunneling current, Zener breakdown, Energy band diagram of pn junction under forward bias, Continuity equation, Boundary conditions, Ideal diode equation, Long- … This is passive element works under principle of Avalanche Breakdown. The Zener and Avalanche breakdown both occur in diode under reverse bias. In electronics, an avalanche diode is a diode (made from silicon or other semiconductor) that is designed to experience avalanche breakdown at a specified reverse bias voltage. Description : Oem 2002 Chevrolet Avalanche 1500 Exterior Trim - Rear Body Parts with regard to 2002 Chevy Avalanche Parts Diagram, image size 485 X 357 px, and to view image details please click the image. A pin photodiode consists of three regions. If a large reverse voltage is applied across the diode, the space charge region is widened from the N + P junction to the IP + junction. The V-I Characteristics of a Zener diode . Found inside – Page 2... 17-34 thru 17-35 Ampere's law , 29-20 , 30-2 Analog bias circuit , 19-10 ... 2-16 Avalanche breakdown , 8-10 Avalanche diodes , 8-13 Average ( real ) ... The following chart will provide you with an initial overview of the connection between the sensitivity of the avalanche photodiode and the wavelength with all photodiodes. While the average duration of this process is assumed to lead to In this mode, Avalanche Diode operates at a high reverse bias condition. The avalanche is quenched, either actively or passively to allow the device to be "reset" to detect further photons. Found inside – Page x... Current in PN Diodes 44 3.11 Energy-level Diagram (ELD) of a PN Diode 45 3.12 Reverse-voltage Breakdown in PN Diodes 46 3.12.1 The Avalanche Breakdown ... Zener diode working Diagram. Electron Dev. Listed below is the vehicle specific wiring diagram for your car alarm, remote starter or keyless entry installation into your 2002- Chevrolet Avalanche.This information outlines the wires location, color and polarity to help you identify the proper connection spots in the vehicle. Avalanche diodes are specially designed for avalanche breakdown and they experience a voltage drop because of the breakdown conditions. These devices use Skyworks well-established silicon technology resulting in PIN diodes with tightly . Schematic Diagram Of An Avalanche Photodiode Ilrating The Scientific Avalanche photodiode Circuit Diagram “File:APD3 German.png” by Kirnehkrib is licensed under CC BY-SA 3.0 For applying reverse bias conditions, the p+ region is connected to the negative terminal, and the n+ region is connected to the battery’s positive terminal. Q GS(pl) Q GD V GS V DS I D t 0 t 1 t 2 t 3 t 4 Q G V GS(th) I D V DS I GG t t t 0 0 Q GS(th) ... Avalanche Energy 2. A standard avalanche pulse generator circuit basically relies on the negative differential resistance in a bipolar junction transistor's avalanche breakdown region to form a relaxation oscillator. The magnitude of the noise is difficult to predict due to its dependence on the materials. Circuit diagram for Overvoltage protection using Zener voltage regulator circuit is given below. Ge-on-Si single-photon avalanche diode detectors: design, modeling, fabrication, and characterization at wavelengths 1310 and 1550 nm. (b-d) Simplified equivalent circuit models and band diagrams of single-photon avalanche diode (SPAD), (b) after the reset process, (c) during avalanche multiplication, and (d) after RQ. Found insideFIGURE 4.43 Band diagram for Zener diode: the top of the valence band on the ... Some devices labeled as high-voltage Zener diodes are avalanche diodes. STUD 1 Fuse l 40A Trailer Wiring / Automatio Level Control Compressor ABS Fuse 52 6OA Brake Pressure Modulator Valve (PumP) IGN A Fuse #3 40A Starter Relay, Ignition Switch IGN 1. The reverse breakdown of a diode can take place due to avalanche breakdown and zener breakdown. The diagram of a normal PIN photodiode is given below. When the p-n junction diode is passed through extended reverse voltage, the minority carriers gain more energy and get accelerated to greater velocities. The diagram shows the basic principle: While the voltage is rising the diode is blocked (A). A Zener Diode, also known as a breakdown diode, is a heavily doped semiconductor device that is designed to operate in the reverse direction. However as the avalanche photodiode is operated under a high level of reverse bias a guard ring is placed around the perimeter of the diode junction. (a) Avalanche Breakdown : When reverse voltage applied to the junction is increased, the amount of energy of minority carrier is increased i.e. The following diagram suggests the standard design of adding an external drain-emitter diode for reinforcing the internal body diode of the MOSFET. The first illustration consists of a battery, a light bulb, and a diode. Found insideThe book provides readers with an overview on the fundamentals and state-of-the-art applications of photon counting technique in the applied science and everyday life. Found inside – Page ixFIGURE TITLE PAGE 28 Coax - waveguide cavity for testing avalanche diode parametric frequency conversion . 72 29 Experimental circuit with coax - waveguide ... Here, you can see the symbol of Avalanche Diode. When an electric field is applied across the junction then the electrons and hole starts moving towards it and got recombine in the depletion region. Avalanche photo diode not to be confused with an avalanche diode is a kind of photo detector which can convert signals into electrical signals pioneering research work in the development of avalanche diode was done mainly in 1960s. Avalanche diode is a special type of semiconductor device that operates in the reverse breakdown region. However as the avalanche photodiode is operated under a high level of reverse bias a guard ring is placed around the perimeter of the diode junction. The internal gain increases the device response. 2002 Chevrolet Avalanche Fuse Diagram 2002 Chevrolet Avalanche Fuse Diagram 2002 Chevrolet Avalanche Fuse Diagram Underhood Fuse Box. Avalanche photo diode (not to be confused with an avalanche diode) is a kind of photo detector which can convert signals into electrical signals pioneering research work in the development of avalanche diode was done mainly in 1960’s. The Avalanche Breakdown and Zener Breakdown are two different mechanisms by which a PN junction breaks. Since the biased voltage is much higher than its breakdown voltage, the SPAD can detect even a single photon. For a given diode, the dominant effect is . New active-quenching circuits are here presented. An avalanche diode is a special type of semiconductor device designed to operate in reverse breakdown region. Found inside – Page 346But Misawa in his p-i-n avalanche diode structure assumed an extended ... Read diode A schematic diagram of Read diode structure n+-p-i-p+ along with its ... The junction of an avalanche diode is designed to prevent current concentration and resulting hot spots, so that the diode is undamaged by the breakdown. A small circuit board that uses a 90 VDC input to generate a user controllable 60 to 80 VDC regulated output with setting and regulation to 0.03 V with 2 uAmp typical load. Found inside – Page 197Such modern avalanche diodes may be regarded as the solid-state analog to ... The basic principle and the electronic readout diagram is shown in Fig. 4.91. From a functional standpoint, they can be regarded as the semiconductor analog of photomultipliers.The avalanche photodiode (APD) was invented by Japanese engineer Jun-ichi Nishizawa in 1952. It results in a large current due to the ionization produced by P - N junction during reverse bias condition. Avalanche diodes, like Zener diodes, are designed to break down and conduct very high currents at a specific reverse-bias voltage. Avalanche Diode Mode. Actual Zener Diode. The SPAD pixels may be overlapped by microlenses to direct light incident on the pixels onto photosensitive regions of the pixels and a containment grid with openings that surround each of the microlenses. Basically the circuit has 2 portions: a zener diode, and MAX2650 Low Noise Amplifiers (LNA). Avalanche diodes are optimized for avalanche breakdown conditions, so they exhibit small but significant voltage drop under breakdown conditions, unlike Zener diodes that always maintain a voltage higher than breakdown. The avalanche breakdown is observed in the Zener Diodes having V z having than 8 V. In the reverse biased condition, the conduction will take place only due to the minority carriers. Energy band diagram 6. Commutating dv/dt Capability 3. External dimensions D • • • STA (10-pin) Absolute maximum ratings. Avalanche photo diode (not to be confused with an avalanche diode) is a kind of photo detector which can convert signals into electrical signals pioneering research work in the development of avalanche diode was done mainly in 1960's. Because the avalanc… When the diode is in the reversed biased condition the minority charge carriers get larger energy from the source and move fastly. Found inside – Page 6-13(6.40) FIGURE 6.13: (a) Circuit diagram of an avalanche diode noise generator. (b) Equivalent RF circuit. The circuit diagram of a avalanche diode noise ... Zener diodes A large area avalanche photodiode detector system with USB interface 1. Avalanche diodes are optimized for avalanche breakdown conditions, so they exhibit small but significant voltage drop under breakdown conditions, unlike Zener diodes that always maintain a voltage higher than breakdown. This electric field exerts a force on the electrons at the junction and frees them from covalent bonds. Commutating dv/dt Capability 3. Duraton: 4 hours. • The concept of diodes is easy to understand with the help of the illustrations below. If switching off results in an inductive load overvoltage peak, it is conducted by the avalanche diode to the IGBT gate and the IGBT is switched back on. An avalanche photodiode (APD) is a highly sensitive semiconductor photodiode detector that exploits the photoelectric effect to convert light into electricity. SEO IGN Fuses The diode The avalanche breakdown is the breakdown mechanism of the PN – junction diodes which have thinner region. It is noted that the series capacitances in ( b – d ) are a summation of the diode capacitance and the stray components. Found inside – Page 2683 Avalanche detector - tunnel diode circuit and sample device . 80 60 40 AMPLIFYING DETECTOR SENSITIVITY , counts / 1. ( 0 ) MARK III DETECTOR ASSEMBLY WITH ... For most diodes, avalanche breakdown is the dominant effect. 271 5 5 silver badges 18 18 bronze badges \$\endgroup\$ 10 The breakdown region graph of the actual Zener diode is not accurately vertical. So, here is an exaggerated energy band diagram for a p-n junction under very . The equivalent circuit diagram is shown below: In a circuit, an ideal Zener diode can be replaced by a voltage source V z, when the Zener diode is operating in the breakdown region. If the input voltage of the circuit goes extremely high, then an avalanche breakdown will occur in the Zener diode. Chart and Diagram Slides for PowerPoint - Beautifully designed chart and diagram s for PowerPoint with visually stunning graphics and animation effects. Avalanche photodiode structure. The initial avalanche current is concentrated mainly in the diode … Dehbop. Cite. Found inside2 Figure 1.2 Band diagram of an impurity band conduction detector , showing absorption of photons and ... 29 Figure 3.1 Avalanche diode design parameters . An avalanche diode is a one kind of diode that is designed to experience an avalanche breakdown at a particular reverse bias voltage. It is used in an electrical system as a relief valve to protect the system from excessive voltage. In this article, we are going to explain Zener diode and its applications in detail. Small Signal Diode. As we increase the applied reverse voltage, the electric field across the junction increases. The PIN diode designs are useful over a wide range of frequencies from below 100 MHz to beyond 30 GHz. avalanche multiplication. avalanche multiplication: A current-multiplying phenomenon that occurs in a semiconductor photodiode that is reverse-biased just below its breakdown voltage. The given diagram explains the avalanche breakdown voltage. This results in the heating of the diode. 2002 Chevrolet Avalanche Fuse Diagram 2002 Chevrolet Avalanche Fuse Diagram 2002 Chevrolet Avalanche Fuse Diagram Underhood Fuse Box. The junction of an avalanche diode is designed to prevent current concentration and resulting hot spots, so that the diode is undamaged by the breakdown. Below is the simple (and quite popular) circuit of a typical avalanche pulse generator based on a 2N3904 transistor. The avalanche breakdown is observed in the Zener Diodes having V z having than 8 V. In the reverse biased condition, the conduction will take place only due to the minority carriers. When a large reverse bias voltage is applied across a p-n junction diode, thermal current starts increasing to a large value. Avalanche Diode Vishay Semiconductor Diodes Division Vishay's diode portfolio includes both high voltage and small signal devices and addresses the full spectrum of electronic systems from industrial applications to the smallest handheld personal multimedia devices. Definition: Avalanche photodiode is a photodetector in which more electron-hole pairs are generated due to impact ionisation. An avalanche diode is intended to experience the breakdown at a particular reverse bias voltage. Found inside – Page 822Figure 31.10 shows the energy diagram of such a device with a reverse ... Avalanche diodes are specially designed to have uniform junction regions to handle ... AVALANCHE DIODE. The avalanche breakdown is the breakdown mechanism of the PN - junction diodes which have thinner region. Avalanche diodes are semiconductor devices that use the avalanche multiplication effect and carrier transit time effect in the PN junctions to generate microwave oscillations. Found inside – Page 905Analog input variable, 310 Analog integrated circuit, overvoltage effects, ... 800 Avalanche diode, circuit, 516 AVX TPS-series, electrolytic capacitor, ... APD Description. In general, it does not allow current, but when the voltage across it crosses the breakdown voltage it starts conducting current. Avalanche breakdown occurs in a pn junction diode which is moderately doped and has a thick junction (means its depletion layer width is high). diodes generator pulse tvs. Avalanche Breakdown is the process of current carrier multiplication due to collision of thermally generated minority carriers with crystal ions in a lightly doped reverse biased pn junction diode.An avalanche of current carriers is produced in a very short time due to this breakdown of pn junction diode. This implies that if the inductive EMF voltage is allowed to pass through an external suitably rated bypass diode, across the drain-emitter of the FET may help avert the avalanche phenomenon. Let me start with a ‘reversed’ idea! Found inside – Page 335The following arrangements have been or are still used : - thermionic diodes - gaseous discharge tubes - avalanche diodes - heated or cooled resistors ... When high reverse voltage is applied to the p-n junction diode, the free electrons (minority carriers) gains large amount of energy and accelerated to greater velocities. Avalanche breakdown usually occurs when we apply a high reverse voltage across the diode (obviously higher than the zener breakdown voltage,say Vz). Found inside – Page 604.3 shows the expected distortion to the diffusion tail for the diode that will be measured. There are four things of note on the graph. As we increase the reverse voltage applied to the Zener diode, these minority carriers tend to accelerated. sEquivalent circuit diagram. It does so by operating with a much larger reverse bias than other photodiodes. It is a semiconductor diode formed by the junction of a semiconductor with a metal. Found inside – Page 207When Ia is equal to this value, the diode becomes an open circuit for this ... The p-n Diode Avalanche Oscillator Most modern avalanche diode microwave ... The first illustration consists of a battery, a light bulb, and a diode. The diode resistance R D is given by the sum of the space-charge resistance and the resistance of neutral regions crossed by the avalanche current. Geiger-Mode Avalanche Photodiodes for Three-Dimensional Imaging 338 LINCOLN LABORATORY JOURNAL VOLUME 13, NUMBER 2, 2002 likely to exceed it. asked Mar 12 '15 at 5:36. Found inside – Page 89(b) Bandgap diagram for sa). ... Another high-speed type is the silicon avalanche photodiode, also operated with a reverse bias voltage. The photocurrent is primarily generated by the defect-state absorption introduced by the boron and phosphorous ion implantation during the PN diode formati … When the voltage across the terminals of a Zener diode is reversed and the potential reaches the Zener Voltage (knee voltage), the junction breaks down and the current flows in . As we increase the reverse voltage applied to the Zener diode, these minority carriers tend to accelerated. In this module on pn junction under bias, we will cover the following topics: Energy band diagram of pn junction under bias, Capacitance-voltage characteristics, Impact ionization, Avalanche breakdown, Avalanche breakdown voltages, Tunneling current, Zener breakdown, Energy band diagram of pn junction under forward bias, Continuity equation, Boundary conditions, Ideal diode . Similar to avalanche photodiodes (APDs), SPADs exploit the photon-triggered avalanche current of a reverse-biased p-n junction to detect incident radiation.