Why lightly doped diode is used in avalanche breakdown?

Why breakdown voltage increase in reverse biased p-n junction diode?

when the p-n junction is heavily doped p-n junction diode has very sharp breakdown voltage.

When diode is heavily doped?

base

Distinguish between zener avalanche effects?

1. Differentiate Zener breakdown from avalanche breakdown? Zener Breakdown Avalanche breakdown 1.This occurs at junctions which being heavily doped have narrow depletion layers 2. This breakdown voltage sets a very strong electric field across this narrow layer. 3. Here electric field is very strong to rupture the covalent bonds thereby generating electronhole pairs. So even a small increase in reverse voltage is capable of producing large number of current carriers. ie why the junction has a very low resistance. This leads to Zener breakdown. 1. This occurs at junctions which being lightly doped have wide depletion layers. 2. Here electric field is not strong enough to produce Zener breakdown. 3. Her minority carriers collide with semi conductor atoms in the depletion region, which breaks the covalent bonds and electron-hole pairs are generated. Newly generated charge carriers are accelerated by the electric field which results in more collision and generates avalanche of charge carriers. This results in avalanche breakdown.

What is the difference between an ideal zener diode and practical zener diode?

Zener diode is heavily doped pn junction diode.

Difference between avalanche and zener breakdown?

A: There is no difference except for a zener its breakdown is known and predictable. Avalanche breakdown is not predictable and usually happens at hi voltage and because of it if the current is not limited it self destroy the device

When a diode is doped with either a pentavalent or a trivalent impurity its resistance will be?

it will increase

How does zener diode work?

The essential guideline behind the working of a zener diode lies in the reason for breakdown for a diode in converse one-sided condition. Typically there are two sorts of breakdown-Zener and Avalanche. 1.) Zener Breakdown This sort of breakdown happens for a converse inclination voltage between 2 to 8V. Indeed, even at this low voltage, the electric field power is sufficiently solid to apply a power on the valence electrons of the molecule such that they are isolated from the cores. This outcomes in development of portable electron gap sets, expanding the stream of current over the gadget. This sort of separate happens regularly for profoundly doped diode with low breakdown voltage and bigger electric field. As temperature builds, the valence electrons acquire vitality to disturb from the covalent bond and less measure of outside voltage is needed. Hence zener breakdown voltage diminishes with temperature. 2.) Torrential slide breakdown: This kind of breakdown happens at the converse inclination voltage over 8V and higher. It happens for delicately doped diode with vast breakdown voltage. As minority charge bearers stream over the gadget, they have a tendency to crash into the electrons in the covalent bond and reason the covalent bond to upset. As voltage expands, the active vitality of the electrons additionally increments and the covalent bonds are all the more effectively upset, creating an increment in electron opening sets. The torrential slide breakdown voltage increments with temperature.

Difference between avalanche and zener breakdown voltage?

"'Zener diode' and 'avalanche diode' are terms often used interchangeably, with the former much more common. Both refer to breakdown of a diode under reverse bias. Specifically, when a diode is reverse biased, very little current flows, and the diode is to a first order approximation an open circuit. As the reverse voltage is increased, though, a point is reached where there is a dramatic increase in current. Equivalently, there is a dramatic reduction in the dynamic resistance (slope of the V-I curve) that can be as low as 1- 2 W in this region.ÝThis voltage is called the reverse breakdown voltage and it is fairly independent of the reverse current flowing.ÝThis property makes it ideal as a voltage reference.Ý "Avalanche breakdown is caused by impact ionization of electron-hole pairs.ÝWhile very little current flows under reverse bias conditions, some current does flow.ÝThe electric field in the depletion region of a diode can be very high. Electron/holes that enter the depletion region undergo a tremendous acceleration.Ý As these accelerated carriers collide with the atoms they can knock electrons from their bonds, creating additional electron/hole pairs and thus additional current.ÝAs these secondary carriers are swept into the depletion region, they too are accelerated and the process repeats itself.ÝThis is akin to an avalanche where a small disturbance causes a whole mountainside of snow to come crashing down.Ý The efficiency of the avalanche effect is characterized by a so-called multiplication factor M that depends on the reverse voltage (Equation 1). Equation 1: Multiplication Factor "Here n is in the range 2 - 6, V is the applied (reverse) voltage, and Vbr is the breakdown voltage.ÝThis is an empirical relationship, as are many of the relationships used to describe both Zener and avalanche breakdown.Ý "Avalanche breakdown occurs in lightly-doped pn-junctions where the depletion region is comparatively long.ÝThe doping density controls the breakdown voltage.ÝThe temperature coefficient of the avalanche mechanism is positive.ÝThat is, as the temperature increases, so does the reverse breakdown voltage.ÝThe magnitude of the temperature coefficient also increases with increasing breakdown voltage. For example, the temperature coefficient of a 8.2 V diode is in the range 3 - 6 mV/K while the temperature coefficient of an 18 V diode is in the range ofÝ 12 - 18 mV/K. "Zener breakdown occurs in heavily doped pn-junctions.ÝThe heavy doping makes the depletion layer extremely thin. So thin, in fact,Ýcarriers canít accelerate enough to cause impact ionization.ÝWith the depletion layer so thin, however, quantum mechanical tunnelingÝ through the layer occurs causing current to flow.ÝThe temperature coefficient of the Zener mechanism is negativeóthe breakdown voltage for a particular diode decreases with increasing temperature.ÝHowever, the temperature coefficient is essentially independent of the rated breakdown voltage, and on the order ofÝ -3 mV/K. "In a 'Zener' diode either or both breakdown mechanisms may be present. At low doping levels and higher voltages the avalanche mechanism dominates while at heavy doping levels and lower voltages the Zener mechanism dominates.ÝAt a certain doping level and around 6 V for Si, both mechanism are present with temperature coefficients that just cancel. It is possible to make Zener diodes with quite small temperature coefficients.Ý "Neither Zener nor avalanche breakdown are inherently destructive in that the crystal lattice is damaged.ÝHowever, the heat generated by the large current flowing can cause damage, so either the current must be limited and/or adequate heat sinking must be supplied."

Why is a gunn diode called a diode?

A Gunn diode, also known as a transferred electron device (TED), is a form of diode used in high-frequency electronics. It is somewhat unusual in that it consists only of N-doped semiconductor material, whereas most diodes consist of both P and N-doped regions. In the Gunn diode, three regions exist: two of them are heavily N-doped on each terminal, with a thin layer of lightly doped material in between. When a voltage is applied to the device, the electrical gradient will be largest across the thin middle layer. Conduction will take place as in any conductive material with current being proportional to the applied voltage. Eventually, at higher field values, the conductive properties of the middle layer will be altered, increasing its resistivity and reducing the gradient across it, preventing further conduction and current actually starts to fall down. In practice, this means a Gunn diode has a region of negative differential resistance.

Why emitter is heavily doped and base is lightly dopped working of p-n-p transistor?

Emitter is heavily doped because to provide charge carriers to Base & Collector region, Base and Collectors are lightly doped because to accept those charge carriers.

What is difference between avanlche break down and zener break down?

The difference between the avalanche diode (which has a reverse breakdown above about 6.2 V) and the Zener is that the channel length of the former exceeds the "mean free path" of the electrons, so there are collisions between them on the way out. The only practical difference is that the two types have temperature coefficients of opposite polarities.

Why inner two layers of scr are lightly doped and are wide?

Explain why the innerlayer two layers of an scr are lightly doprd and are