Questions tagged [pn-junction]

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How temperature difference does not affect transistors in CPUs?

Recently I learned about semi-conductors and some devices. Today I watched a video on youtube about a guy overclocking a cpu to 7.0 ghz, while cooling it with liquid nitrogen to -192 celsius degrees. ...
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20 views

carrier concentration of PN junction

i am trying to calculate these formulas: -and- (p-side: x < -xp , n-side: x > xn) But i wonder, how can i find pn0 and np0 Thanks in advance.
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36 views

carrier concentration - distance graph of PN junction

i am trying to plot the distance-carrier_concentration graph above with these formulas: -and- (p-side: x < -xp , n-side: x > xn) But i could draw only red lines on the graphs with these ...
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1answer
44 views

Is the current in reverse biased PN junction due to drift or diffusion?

Wikipedia says The saturation current (or scale current), more accurately the reverse saturation current, is that part of the reverse current in a semiconductor diode caused by diffusion of minority ...
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1answer
48 views

How can a tunnel diode be used as a memory element?

I read in applications of tunnel diodes that it can be used as a memory element. I am not able to justify or verify this statement. It would be very helpful if a circuit showing logic storage using a ...
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1answer
58 views

In the solution to this problem, why is the electron charge omitted?

The problem reads as follows: A silicon pn junction with a cross-sectional area of 10-4 cm2 has the following properties at T = 300K: n region: \$N_d = 10^{-17} cm^3\$ \$\tau_{p0} = 10^{-7} s\$ \$\...
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1answer
57 views

How drift current is independent of bias voltage in semiconductors?

According to my textbook: The drift current is relatively insensitive to the height of the potential barrier. The reason for this anomaly is the fact that the drift current s limited not by how fast ...
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1answer
400 views

Why are PIN junctions better for solar cells than PN junctions?

In lecture today my professor mentioned that PIN junction make better solar cells than PN junctions. Why is this true? The PIN junction will have a wider depletion region which means it'll have a ...
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44 views

What does the fermi-level increase in reverse-bias?

Fermi-level tells us the probability of finding an electron at 50%. When you look at an energy band diagram in reverse-bias you can see the Fermi-level increases in the p-type semi-conductor. Why does ...
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26 views

In an energy band diagram why is the valance band in the p-type have more energy then n-type?

I am having trouble understanding energy band diagrams. In an energy band diagram of a semi-conductor during equilibrium the valence band of the p-type is higher then n-type meaning electrons in the ...
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2answers
75 views

Why does a p-type conduction band have higher energy then n-type conduction band in a p-n junction?

In an energy band diagram that represents the p-n junction (during equilibrium) the p-type conduction band has greater energy then an n-type conduction band. Why does the p-type have greater energy ...
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1answer
90 views

Bringing P type and N type semiconductors together in vacuum

Consider the case where a P-type semiconductor and an N-type semiconductor are placed in perfect vacuum. Now, the two junctions are brought together. In the time immediately after they are brought ...
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39 views

Minority carrier current in p-n junction diode

Does minority carrier current flow through p-n junction even in the absence of any external applied voltage?Is minority carrier current same as reverse saturation current?
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1answer
54 views

Blocking voltage of diodes

What exactly is blocking voltage in relation with Metal-semiconductor junction diodes? Is it related to breakdown voltage?
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1answer
83 views

Are there two band contributions to diffusion current at the PN (diode) junction?

My question (I hope) is a simple one. Are there two components of diffusion current (valence band AND conduction band) contributing to the generation of the PN junction voltage? If so, do those ...
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2answers
118 views

Nature of conventional current flow in a p-n junction

More specifically, I'm confused about the concept of hole diffusion. I can understand that electrons diffuse towards the p-type material. However, the concept of holes diffusing is a little bit ...
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1answer
89 views

What are the typical paths of holes and electrons in an unbiased PN junction?

Can anyone tell me the typical paths of holes and electrons in an unbiased PN junction at equilibrium? In terms of diffusion currents, is that only holes (majority carriers in the the P-Type) ...
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2k views

Perpetual machine from a PN-junction diode

Consider a PN junction diode Now, this system will naturally form a depletion region due to diffusion and will convert into this: Now, I wish to connect the ends of this diode with a conducting wire ...
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1answer
53 views

p-type and n-type solids

Is the difference between p-type and n-type solids simply the difference in the placement of the valence and conductive band in the solid. Otherwise I fail to understand, p-type means lots of holes ...
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36 views

What is the effect of larger dopant concentrations in a pn-junction diode?

When we increase the concentration of dopants on both the sides of a pn-junction diode, how do the I-V characteristics change? In particular what is the effect on breakdown voltage and forward knee ...
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3answers
158 views

The potential drop in a pn junction diode-

In the picture shown above, I was trying to learn about diode equivalent circuits. I am not being able to understand the direction of Vb taught by the instructor here. The question is- If the n region ...
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1answer
57 views

Why do point contact diodes use wire whiskers?

I've recently been learning about the operating principles of various semiconductor devices, and I've run into difficulty regarding the point contact/metal-semiconductor diode. I can't find out why ...
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1answer
45 views

Metal semiconductor Junction

As we know in normal p-n junctions is formed by doping on a single semiconductor so that material continuity is maintained which facilitates the movement of charge carriers between two regions. But in ...
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44 views

ploting the recombination rate in a forward bias depletion

I'm trying to figure out how to plot the graph in b. I know I need to go according to the recombination formula in a, and Ei is linear, but for some reason something won't work. is there anyone who ...
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19 views

Can anyone represent the formulas of excess carrier concentrations of electrons,holes respectively using the differences?

I've been doing the assignment and the statement is as below. $n_p0 := minority carrier concentration of n-type semiconductor in which no forward bias voltage.$ $p_n0 := minority carrier ...
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14 views

how does the n+ p junction look like when the width of p layer is so small?

How will the carrier concentration and the band diagram in a n+ p junction will look like when the p region is cut short before the actual barrier width? (or) In other words how does the n+ p junction ...
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36 views

Voltage across the depletion region after applying voltage

Consider a pn junction at equilibrium. If we apply a voltage across the diode, neglecting resistance of neutral regions, all of the voltage should drop across the depletion layer. Therefore if we ...
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2answers
145 views

Why doesn't light destroy the PN junction voltage gradient in a solar cell?

I understand that a solar cell is, essentially, a P-N junction. A P-N junction, roughly speaking, will do the following: The free electrons on the N-side will flow over to fill holes on the P-side. ...
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1answer
139 views

Can anyone explain reverse bias pn junction using only electrons as charge carriers

In forward bias condition p-type semiconductor is connected to positive side and ntype semiconductor to negetive side and the electrons flow from n-type to p-type to cathode of battery. But imagine ...
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1answer
125 views

Problem in understanding transistor

I am a high school student. We are taking transistor in our class but I couldn't understand the topic. I have read several answer on this site both for physics as well as electrical engineering stack ...
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32 views

Carrier concentration of pn junction in reverse bias

I'm trying to understand the effect of forward and reverse bias in the carrier concentration of a pn junction. I know that in equilibrium the first picture below holds. When we apply forward bias, the ...
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1answer
82 views

Diode lifetime VS junction temperature

I have one bridge rectifier operating at the constant junction temperature of ~72°C, (GBPC3510W datasheet), which is rising to ~80°C in some specific cases. I'm trying to find a kind of "aging curve" ...
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3answers
98 views

Total current current equation in P-N junction

So Okay I get why there is a negative sign in the equation for diffusion current of holes since the gradience is actually negative if we put our coordinate axis in the bottom left corner for example ...
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1answer
81 views

Given a diode circuit and some of its values, how do I find the temperature?

Let's say I am given the following circuit: along with $$dV_p/dT=0.139mV/K$$: Defining V1 the voltage above Diode D1 and V2 the voltage above diode D2 , we use the expression for the current of a ...
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2answers
388 views

Deviation from typical I-V characteristics of a diode in high frequency

Why the diode shows a loop in the I_V characteristics?(Diode part N4003, Frequency was 100k) My instructor told me something regrading the retardation of charge carriers but I couldn't understand/find ...
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1answer
95 views

How do LEDs stay on constantly?

In a LED (light emitting diode,) a forward bias allows electrons to fill the vacancies in the p-type region, recombining with holes to emit a certain frequency of light. After a set amount of ...
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2answers
94 views

Confusion regarding Common-Emitter configuration of a BJT

This is a picture of a Common-Emitter Configuration of an n-p-n BJT, taken from a book :- For the BJT to be in active mode, the Base-Emitter junction should be forward biased, and the Collector-Base ...
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1answer
65 views

Photodiodes: the “generation” mechanism behind photocurrent

Assume I use a photodiode under zero-bias (that is in photovoltaic mode). How/why can a current flow in this bias condition? As far as I have understood the working principle of photodiodes, when ...
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47 views

Calculating Nmax in loaded bipolar junction transistor inverter

I have tried various methods for calculating N max here, and some have resulted in negative answers while others have resulted in an answer of around 1. Is my method correct? Or am I missing ...
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2answers
181 views

P-N Diodes in series. Is my solution correct?

I have attempted to work out a solution on a short question relating to p-n diodes. Is my solution correct? The question (from a past paper) : From the question I understand that there are two ...
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2answers
67 views

Forward Bias PN Junction

The depletion region is formed at the junction due to diffusion which creates a thin width of negative ions on the p side and positive ions on the n side whose electric field restricts further ...
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2answers
81 views

What bias voltage is applied to a PIN photodiode when connected only to multimeter

If I take just a PIN photodiode (e.g. BPW34 FAS ) and connect a multimeter to its terminals to measure current, for example: expose the photodiode to the sunlight and read current of ~1 mA on the ...
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1answer
71 views

Barrier voltage and temperature of a PN junction

Why does the barrier voltage of a PN junction decrease by increasing temperature ? Please if possible , i want to understand the inner physics of what happens
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3answers
281 views

BJT Active mode - How does it work

I am finding it difficult to understand how exactly this works and would appreciate any help. From my understanding: The emitter base junction has to be in forward bias meaning that Vb is more ...
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2answers
394 views

Find cause of diode destruction from destroyed diode itself

Is it possible to find the cause of power diode destruction, ie. if it was destroyed through: reverse overvoltage spike (reverse breakdown and subsequent thermal destruction due to reverse ...
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1answer
168 views

Estimate temperature for silicon (p-n junction)

I need to estimate the temperature at which p-n junction made of silicon lose it rectifying characteristics. (\$N_A=N_D=10^{15}\,cm^{-3}\$) \$E_G\$ is independent of the temperature and are 1.12 eV ...
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45 views

Diodes when voltage is applied

Does the hole injection take place from p semiconductor to n semiconductor in a pn junction diode? Or it takes place only in the case of a transistor?
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1answer
101 views

Thermal drift in diodes

Hi guys and thanks for reading and your help. I can't understand a thing that my book says: "When the temperature grows, the diode will let flow more current" and then it gives 2 formulas: \$V_t = \...
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1answer
1k views

Drift current in PN Junction

Ok guys, first of all thanks for your support and your help, I can't understand how the drift current work, let's say that we have this junction By the definition of the drift current we can ...
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3answers
206 views

Why not all the diodes are in “on state” in the given picture?

Given:"all the diodes are ideal",in figure (e), only D3 is on and rest of the two diodes are given off in the solution. Similarly for (f) only D1 is on. I don't understand the logic behind this. ...