Questions tagged [semiconductors]

Most generally a class of materials that are neither insulators or conductors in their natural state but which can be manipulated via doping or electric fields to change the conduction state. Silicon, Germanium, GaAs are some usual materials. The term is also used to speak about devices that are made from such materials. For example a processor from Intel can be called a semiconductor.

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Is there any specific application for an indirect band gap semiconductor?

I know that direct band gap semiconductors are very attractive for optical emission, and even though indirect band gap are used as well, I keep wondering: is there any technology that specifically ...
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What is the correct carrier concentration equation to use?

In this book I am reading, it gives the intrinsic carrier concentration as: \$ n_i = \sqrt{N_c\cdot N_v} \cdot e^{({\frac{-E_g}{2*K*T}})} \$ While another book says the carrier concentration is: \$ \...
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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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High frequency switching applications

I was reading that for high frequency switching applications with semiconductors, the ratio of the electron to hole mobility should be high. Why is it so? Is it a necessary condition always? Or ...
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Photo-conductivity of n and p type semiconductors

Both n-type and p-type semiconductors are available to fabricate a photoconductive devices. To achieve the highest photoconductivity, do you want to use n-type or p-type? Why? $$σ_{ph}=q(μ_n ∆n+...
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Why is the common emitter input insensitive to base width modulation?

According to Robert F. Pierret (1996) in page 411 of the 2nd edition of the textbook Semiconductor Device Fundamentals, common emitter input of PNP BJTs is insensitive to base width modulation. Isn't ...
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Why BJT thermal voltage can be not equal to kT/q in SPICE3

In SPICE, apart from effects such as basewidth modulation and base-collector leakage the collector current is given by the expression (according to the original SPICE2 PhD work) But actually, ...
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Purpose of field implant in semiconductor manufacturing

I recently joined the semiconductor manufacturing industry. In one of the process flows, I see a stage that has extra boron implantation step (called the field implant) in the P-WELL region. I've ...
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Why does the majority carrier concentration near the junction not decrease under forward bias? (PN junction)

We see that the current due to the majority carrier decreases near the junction as shown above, which means the majority carrier concentration should also decrease since the diffusion current is given ...
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How does the stored charge gets decayed when going from forward bias to zero bias?

In a pn junction diode when forward biased, excess electrons and holes get stored in p and n regions respectively. If we short the diode by connecting p,n terminals with a wire, how do these stored ...
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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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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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Connecting phototriac substrate to adjacent pins

For a regulatory exercise I am analyzing the result of a short fault between a phototriac's substrate (MOC3023) and its anodes (one at a time). The datasheet warns ...
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Is there a way to experimentally separate the effects of gate voltage?

I'm currently doing experiments on new kind of semiconductors. These devices have a body (source, drain) and a top gate. These devices show a response to gate voltage. The conductance changes with ...
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How does a MOSFET conduct in saturation region?

It is a simple question but I could not find a straightforward answer. When a MOSFET enters saturation region, the channel length starts to decrease, and the channel width is the smallest near the ...
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Why in a MOS device the depletion zone width doesn't increase if the applied voltage is over threshold?

If a positive tension V is applied in a MOSCap, the depletion zone width will increase until the threshold voltage is reached. If the applied tension is above the threshold voltage the depletion layer ...
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Semiconductor physics, effective mass calculations, band edge. vs. DOS vs cyclotron resonance

I am trying to understand effective mass for electron carriers in the conduction band as found in experiments. I am using the equations in a simulator. The simulator models power mosfets from -85C to ...
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How much of a surface mount PIN diode is semiconductor?

The problem: manufacturers provide a lot of information on the operation and characteristics of the devices, but not on what's inside. I'm trying to incorporate the effects of a surface mount PIN ...
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Semiconductor Level Genetic Programming

I was reading a most likely old article about, Adrian Thompsons work on using genetic programming to generate circuit solutions for simple tasks such as frequency differentiation. This got me ...
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Does the Black's equation work for immortal wires / interconnections (or only for mortal ones)?

I'm trying to understand whether the Black's equation is only true for mortal wire / interconnections or it is also applicable to immortal wires (essentially when its \$jL\$ product is less than \$jL_{...
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How to calculate the total power of a LED using solid angle?

I have a LED with the max power of 130mW/sr and an opening angle of +-10° (so approx. around 20°). I conducted an experiment using this LED, the LED shines light to an un-doped silicon semiconductor ...
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Has any implementation succeeded to have shared key inside chipset and protect it from exploits?

Since there is a lot of demonstration like using SEM (Scanning Electron Microscope) to read bits from ROM through the scanned image of chipset, is there any implementation that has managed to succeed ...
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MOSFET gate substrate voltage

In a MOSFET the channel is formed between gate and the body it would sense to use gate body voltage to form the channel. Why is gate source voltage used to form the channel?
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Designing BJT that's beta value is 120

I want to design a BJT that's beta value is 120 Following this picture can I say that the components of the base current are like this? J(B) = J(pE) + J(R) + J(RB) - J(G) - J(pC0) I want to design ...
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(Too?) simple model of a pn junction

I want to build a simple model of a pn junction in order to show high school students how it works. I am not looking for something precise, so I use really simple discretization and I discard units. I ...
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Solar cell DIY with monocrystalline silicon wafer

I would like to make my own solar cell- From a quick search on youtube, these 2 videos are apparently always the #1 result for "solar cell diy" keyword or similar: Video 1 Video 2 The ...
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IGBT modelling from datasheet

how to model igbt from the APT150GN120J datasheet. ...
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Mobility of electrons vs holes in semiconductors (intrinsic vs extrinsic)

I was reading my class notes and it was written that electrons are more mobile than holes because the effective mass of electrons are lower than that of holes. (μ=eτ/m*) I checked online to find the ...
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Calculation of Rated Power for IGBT Module

For an IGBT module with the following characteristics, how can we calculate the rated power? I mean how much is the rated power for this module?
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How can you measure voltage differences less than thermal voltage (~26mV at room temp)?

If thermal voltage is the average voltage of any given electron relative to the voltage at ground state, and this presumably fluctuates, how can you make any measurement on a circuit more accurate ...
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Unknown logo on FGS25N120ANTD IGBTs. Which semiconductor manufacturer is this?

I bought 5 FGS25N120ANTD IGBTs from my local vendor a while back. I was unable to identify the manufacturer, based on the logo. Can somebody help me out?
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Semiconductor mass action law question

I was told that the mass action law $$np = n_i^2$$ only applies to compensated semiconductors and intrinsic semiconductors, and it does not apply to n-type or p-type semiconductors. Is this true? I ...
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Can anyone properly explain me the characteristic curve of the p-type JFET?

I know how a MOSFET works. But recently I wanted to know details about JFET. When V(GS) = 0 volts there will obviously a current flowing through the p-type channel. What confuses me is how the ...
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IGBT chip metalization

Consider an IGBT chip within a power module. The top surface of the chip is often metalized by aluminum (with approximately 5 microns thickness) to bond some aluminum wires into the chip; I am hazy ...
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What happens if doping concentration is less than Intrinsic concentration? Will the semiconductor act as intrinsic or extrinsic? Please Explain

Si has intrinsic conc of 1.08*10^10 If it is doped with conc less than intrinsic concentration what happens
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BJT transistor working and construction

Why is electron concentration zero at collector side of the base in BJT transistor? And if electron concentration decreases with distance and becomes zero at the end base region how can it produce ...
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Single Crystal Growing and Orientation (Silicon) using Czochralski Process

I'm working on small bibliographic research on photovoltaic panels, and I have chemistry background. I have confusion on crystallization (Czochralski method) imposed by the seed and following specific ...
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Identity and advice on replacement of SM diode

I have a Sonos Play:3, which is past its warranty. I dismantled it to find it has the well documented fault with a blown capacitor. However, there is also damage also to one of the surface mount ...
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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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Failures on underside layers of a chip in IGBT power modules

Does somebody know how I can detect a layer of IGBT modules in which a thermal failure, e.g., voids, cracks, delaminations of solder joints, has taken place? We know there is fatigue in both solder ...
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Can you buy Aluminum Nitride transistors?

We all know wide bandgap semiconductors, currently galium nitride and silicon carbide are the superstars becose many companies make them at relatively reasonable price. They aren't just mere lab ...
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Peltier Module constant time and thermal Load

Hi everyone I am new to this forum. I am doing a project where I need to control one of the sides temperature of a Peltier device against human skin. So one side is in contact with the skin, and the ...
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2 answers
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Discerning between transistor types

How do you tell different semiconductors (mainly transistors, sometimes even voltage regulator ICs, etc.) apart? Do they all basically look the same; or are there visual clues to indicate a certain ...
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What kinds of semiconductors are used for high voltage devices?

IIRC, gallium nitride is one of them. But what about silicon? What do they use for making thyristor valves found in High Voltage Direct Current power stations?
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What does the channel voltage in a MOSFET really mean and how does it lead to the Fermi level splitting shown?

Many books (Chenming-Hu Ch.6 Page 15, Neamen Page 413) use the term 'channel voltage' \$V(y)\$ to mean 'the potential in the inverted channel at a point \$y\$ distance away from the source along the ...
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In this semi-ideal photodiode, what would be the physical interpretation of this current?

A real photodiode can be expressed as a circuit made of several ideal components, it looks something like this: simulate this circuit – Schematic created using CircuitLab I copied it from here ...
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Why is the diode reverse biased in the determination of energy gap?

I know that the energy gap increases when we reverse bias the diode, but I still don't see why forward bias won't do the trick. How exactly does the width of the band gap matter in measuring it? A ...
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Current density in an ideal pn junction diode

I found that the current density is as above. I am going really crazy with this problem as I can't get any clue from anywhere. I have been googling for 10 hours and have no idea. Please help. The ...
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BJT NPN transistor

I am confused on a topic regarding NPN BJT transistors. When there is a collector-emitter voltage (VCE) applied to the NPN transistor (as shown in the figure) without a emitter-base voltage (VBE), it ...
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Why does the Schottky barrier height remain constant?

If a metal and a semiconductor are connected, they are going to equilibrium. For this, the Fermi level has to be equal. So far I understood that this causes a charge exchange till said equilibrium has ...
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