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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 ...

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Why does the minority carrier concentration increase exponentially towards the junctions in a forward biased power diode? (graph included)

[Image Source: Power Electronics - Converters Applications and Design by Ned Mohan] Let's take the p+ side. Since the anode is of a higher potential (forward bias), shouldn't the electrons (minority) ...
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IGBT: Ic in terms of Tj, Vce and Vge

The graph below is for IGBT (part number: ifs75b12n3e4_b31). Could somebody give me a relationship for Ic in terms of junction temperature (Tj), Vce, and Vge?
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How deep does the depletion region in power diode penetrate the lightly doped n- layer under no bias?

I could find references for describing the depletion layer in a power diode under reverse bias and the consequent classification of Non-punch through and Punch-through diodes. But I couldn't find a ...
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485 views

Why do power diodes have a p+ n- n+ construction and why not p+ p- n+?

I've been learning about power diodes and how they differ from low power diodes with the addition of a lightly doped n-type layer. This n-type layer improves the breakdown voltage rating of the ...
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1answer
25 views

Ic and Vce equations of IGBT

I know in IGBTs while operating, parameters Ic (collector current) and Vce (collector-emitter voltage) are Tj (junction temperature) and Vge (gate-emitter voltage) dependent. Is there anything else ...
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31 views

Calculation of Vce from Ic-Vge Characteristic

We have found the Ic-Vge (collector current vs gate-emitter voltage) characteristic of an IGBT device as shown below at a high Vce (collector-emitter voltage) value (here 20V) from the datasheet (...
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1k views

Are some CPUs implemented in standard cells and are others customized?

Explaining the question more, I see some die pictures which are implementing a Cortex-M0, with Bluetooth LE and so on, depending on the chip functionality, and are appearing like this (nRF51822): ...
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Performing Capacitance -Voltage characteristics under different temperatures.

Performing Capacitance -Voltage characteristics under different temperatures. The higher the temperature, the higher the capacitance measured for the same device(capacitor). As far as is know this has ...
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31 views

Ic-Vge IGBT Curve

In the figure below, presented in the manufacturer datasheet, you can see the Ic-Vge curve of an IGBT device. As mentioned, it has been drawn at Vce=20V. What does this equality mean? Can we have such ...
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38 views

Are both electrons and holes responsible for conductivity in an extrinsic semiconductor (both n-type and p-type)?

In a semiconductor, the drift velocity Vd and E(electric field intensity) are directly proportional to each other.. with the proportionality constant as mobility of charge carriers.. in the formula I ...
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55 views

Can really small transistors be modeled as in undergrad textbooks?

Most undergrad textbooks on microelectronics (those covering semiconductors, diodes, BJT's, FET's, etc.) that I have laid my hands on discuss semiconductor concepts such as charge carries, drift, ...
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70 views

What do we mean by “gate plateau voltage”?

While reading some semiconductors datasheets, I've found something called "gate plateau". What do we mean by this term ? Reference: AND8029 application note page 2, from ON Semiconductor written by ...
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1answer
152 views

Large SiGe ASICs for digital logic

I am trying to understand if digital ASICs with tens of millions of silicon-germanium gates exist. A comment in another post states (emphasis mine) "SiGe can hit 5 GHz pretty easily even with half a ...
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4answers
531 views

Exotic semiconductors for fast digital ASIC

I am researching exotic semiconductors for a digital ASIC with a few million logic gates which should run as fast as possible within a $30 million budget. (Specifically, I need to do a single fully-...
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1answer
43 views

How could the Gate-Source potential difference be neglected?

I’ve been reading the book Electronic Principles by Malvino In the Voltage-Divider bias section of JFET, if gate current is negligible then how did Gate Voltage attain a negative value, given Vdd ...
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1answer
51 views

MOSFET common source amplifier output impedance calculation

What I've read in microelectronic texts like Prof's Razavi's Fundamentals of Microelectronics is that for calculating output impedance, one has to make all independent sources 0, i.e., short all ...
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2answers
58 views

Why conductivity increases in semiconductor when doped?

I know it depends upon the concentration of electrons and holes . So if we add donor atoms, even though electron concentration in conduction band increases , hole concentration decreases due to more ...
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1answer
31 views

Why in semiconductor studies, we are only concerned with reduced zone representation of e-k diagram?

Does electron transition from conduction band to valence band takes place only in first Brillouin zone? Or can it happen in any other Brillouin zone?
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Diode current components

I have the following two questions in the derivation of current in a diode. 1) In forward bias, an assumption "abrupt junction" is made and field is equal to 0 is also made. But then we still use ...
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2answers
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Measuring junction temperature of LED tape?

My boss at work wants me to figure out a method of measuring the junction temperature of an LED that is part of a reel of tape. Unfortunately, there is no datasheet for the LED modules themselves, ...
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1answer
51 views

Simple diode question

I have the following doubts about a p-n junction diode: 1) If we short the diode ( connect it's terminals together without any power source) then how is the Kirchoff's law across the loop satisfied? ...
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3answers
974 views

How should I understand the intrinsic body diode inside a MOSFET?

I know there is an intrinsic body diode inside all the MOSFETs, but I'm confused about the reason why it's there. I've searched the articles but can't find a good explanation for it. Can anyone use ...
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2answers
264 views

Why won't this DIY transistor attempt conduct

I've been trying to make a crude transistor device at home. So far I have not been successful. My electrical understanding is next to non existent other than what I've learned in the last 3 months ...
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1answer
57 views

Why carriers move when Electric field is applied on Haynes-Shockley experiment

I would like to know why excess carriers/minority move when an electric field is applied at the Haynes-Shockley expirement
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7answers
162 views

Confusion regarding this Op-Amp circuit

So I have started learning about Operational Amplifiers. In case of idea Op-Amps, Vd=0 as amplification is very large and Vo is limited by Vcc(the supply voltage). Here in this inverting Op-Amp ...
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1answer
150 views

What the difference between pin and pn diodes i-v curve?

For my understanding there should be no big difference in i-v curve between regular p-n junction and p-i-n junction, the only difference i can think about is do to the bigger resistance of the ...
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1answer
94 views

Confusing regarding measuring barrier potential of a pn junction using a voltmeter

I have been trying to understand why we can't measure the Barrier potential existing in an unbiased pn diode but on seeing the answers I am quite confused. There seems to be two answers to this ...
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45 views

Variation of Fermi level in doped semiconductor with applied voltage

Is Fermi level of p or n type semiconductor constant with respect to applied voltage ? Please explain. From the attached image it seems Fermi level of intrinsic semiconductor varies but that of ...
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2answers
70 views

When Pin diode is no longer junction?

For p-i-n junction with intrinsic region d, I need to answer what happens when d is very large. So from simple logic, I believe that at some point there will be no diffusion of charge carriers from p-...
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1answer
64 views

on-state voltage

I am trying to study an ever-on IGBT. in other words, IGBT is tried to be on in a long time. To this purpose, a +15V constant dc voltage is applied to the gate-emitter. But, when connecting a +2V ...
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0answers
53 views

MOS Capacitor Band Edges

I am trying to understand the MOS-Capacitor band edge shapes. When negative voltage is applied for gate, why does the band edge across the insulator shift upward (and linear decreasing band edge)? ...
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2answers
118 views

Equivalent circuit of a photodiode

What can I learn from an equivalent circuit model of photodiode like the following? I've actually gone the whole way beginning from doping semiconductors through each noise term to the amplification ...
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2answers
53 views

semiconductor equilibrium and steady state

Why should equilibrium imply steady state? For example, there is a process whose rate increases with time and this process can be exactly balanced by an inverse process whose rate also increases with ...
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2answers
548 views

What does the second code on transistors mean?

I have several transistors, I understand that the last digits on the first line define what the transistor is. There's a second code as well. I've added some photos. What does this code mean?
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1answer
63 views

Identifying the logic function of this specific MOS layout

I am not sure about the functionality of the following MOS layout. I came up with the logic function AND(NOT(AB),C). Can anyone confirm or correct me ? PS: The steps I made are attached
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47 views

Non-uniform temperatue distribution

Please assume a semiconductor chip like IGBT or MOSFET heated by a specific power loss. It is found that the more the power loss is, the more severe the chip's temperature distribution non-uniformity ...
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1answer
105 views

Electrons and Holes in a semiconductor

In an exercise I have an un-doped silicon I find that p=1.80e+11 ,n=6.60e+10 , should the numbers be more close to each other? (for example in GaAs I find 1.10e+14 and 1.60e+14)?? (also p number of ...
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2answers
19 views

What properties can be changed to maximize a p-n diodes effectiveness at higher temperatures? [closed]

So the reverse bias breakdown voltage of a diode gets smaller as temperature increases. What can be done to change that? Can the concentration of dopants of the p or n layers be changed to make this ...
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1answer
47 views

Conceptual understanding of semiconductors - definition of holes

I am studying semiconductors and I have a very basic question on the definition of a hole. Why do we add up the contributions of holes and electrons when calculating the current density ( J = (n.q.un +...
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79 views

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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1answer
548 views

Why is Junction Temperature called so?

Why is the silicon die temperature inside a semiconductor device referred to as "Junction" Temperature ? Though this name may make sense for minority carrier devices where there is maximum power ...
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0answers
30 views

Changing gate threshold voltage in IGBT

I want to divide a semiconductor chip into two sections and then build two different gate threshold voltages (Vth) for the sections. How can I do it? I think it should be done by methods (maybe by ...
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1answer
360 views

Difference between Vth and Vge?

What is the difference between the threshold voltage (Vth) and gate-emitter voltage (Vge) for IGBT devices? How can I calculate Vth of an IGBT chip?
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1answer
144 views

MOSFET pinch-off [duplicate]

I have difficulties understanding what happens in MOS-FET-pinch-off: Take an N-MOSFET: Near the source the gate-bulk voltage is high enough to form an inversion layer. So we have electrons as ...
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2answers
58 views

Can a semiconductor device discharge power capacitors

Trying to figure out how to discharge a capacitor yielding 75 Joule - 177v @ 4700uf. I am uncertain which or even if a semiconductor device is up to the task. Can semis do it? If yes then which can do ...
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1answer
94 views

GaN & SiC piezoelectricity problematic?

I read that galium nitride and silicon carbide are piezo materials.Does this cause some problems? I can imagine that unwanted piezoelectricity directly in the circuit path would cause some kind of ...
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1answer
30 views

Temperature-Dependent Electrical resistance Si and SiC

In a power electronics device, it seems that silicon carbide (SiC) has a higher variation of electrical on-state resistance with temperature in comparison to silicon (Si). Does anybody know the reason?...
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2answers
136 views

Identifying parts of a transistor die

In books, I have studied that in a Transistor, the Base is the layer sandwiched in between Collector an Emitter. Wikipedia also mentions that "The base is physically located between the emitter and ...
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2answers
121 views

Does an LED’s free electrons ever run out?

I’m aware that LEDs are doped with impurities on each p-type and n-type material to increase the charge carriers of each semiconductor. My curiosity now is, how does each side continue to have extra ...
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2answers
92 views

Accurate explanation of diode reverse bias mechanism

For quite some time I haven't been able to convince myself how reverse bias works using conventional explanations that involve words like 'minority carriers', 'majority carriers' etc. which do not ...