# diode3

## What is law of junction?

The law of junction states that in a semiconductor bar with two points at potentials V1 and V2 with concentrations P1 and P2, then P1 and P2 are related to V1 and V2 by

P1 = P2*exp ((V2-V1)/Vt), Where Vt is voltage equivalent of temperature

## Explain the signification of η in diode current equation?

In deriving the current equation for diode the carrier generation and recombination in the space charge region is assumed to be negligible. Such an assumption is valid for germanium but not for silicon. Hence in order to take them into account the factor η factor is introduce in current equation.

## What is the η value for germanium and silicon?

The carrier generation and recombination in the space charge region can be neglected for germanium but not for silicon. Hence

η = 1 for germanium

η = 2 for silicon

## Draw the IV characteristics of the diode?

Diode IV Characteristics

## Which diodes will operate in reverse bias?

Following are the some of the diodes which operate in reverse bias

a) Zener diode

b) PIN Diode

c) Varactor diode

## What is Diffusion length of electrons and holes?

The average distance hole or electron travels before it recombines with electron or hole subsequently is called as diffusion length of holes or electrons. This is denoted as Lp (holes) and Ln (electrons). The unit is Meters.

## Define Carrier Life time of holes (or) elections in a semiconductor?

The average time a minority carrier hole (or) electron survives before it recombines is called carrier life time.

## What is the Relation between diffusion constant lifetime and diffusion length in diode?

Diffusion length Lp=Root (Dp * Tp)

Where Lp = Diffusion length of holes in meters

Dp = Diffusion constant of holes in m2/s

Tp = Carrier life time of hole sec

## What is Einstein’s relationship between diffusion constant and mobility?

The Einstein’s relationship between diffusion constant and mobility is

Where Dp, Dn are diffusion constants for holes and electrons; µn, µp are mobilities of electrons and holes, Vt is voltage equitant of temperature.

## What is voltage equivalent of temperature and its value at room temperature?

The voltage equivalent of temperature is defined as

Vt = K*T/q

Where K is Boltzmann constant = 1.38*10^-23 joule/Kelvin

T is absolute temperature in Kelvin

Q is electronic charge = 1.6*10^-19 coulombs

At room temperature of 27 Deg C (300 K) it is approximately equal to 26 milli volts.

## What is low level minority carrier injection in diode?

The term low level minority carrier injection is used when the injected minority carrier concentration (holes in n material, electrons in p material) is very less compared to majority carrier concentration i.e. doping level. For example holes are injected into n type semiconductor due to some excitation say electric filed low level injection condition is satisfied when injected hole concentration << electron concentration.

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