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Questions tagged [semiconductor-physics]

Semiconductor physics is the branch of solid state physics that focuses on specific properties of semiconductors. It studies dynamics of different perturbations (mainly electrons and holes) in the semiconductor crystal and the ways to harness it in electrical circuits.

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Reverse bias under 0.7V

Assume we have a diode. Well, I was wondering what is happening if we connect the negative terminal of the battery to the p type region and the positive terminal of the n type region to the positive ...
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23 views

MOSFET Body terminal

What is the point of the body terminal in a MOSFET. If we assume Vsoure=0, Vdrain>0 then we will have a linearly changing voltage from drain to source. Then if Vgate>0 , depending on the difference ...
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MOSFET operation

I have 2 questions about the the MOSFET operation. When we apply voltage at the gate is the depletion region between the drain and the p type semiconductor destroyed? If we put a resistor to the ...
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Is the current flowing through a zener diode in forward bias greater than the current flowing through an ordinary pn junction diode in forward bias?

Does current flowing through a zener diode, when forward biased, increase due to heavy doping?
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Reverse bias voltage drop

In reverse bias , when we go up the breakdown voltage why is there a voltage drop across the diode?.I mean the diode does resist to the flow of charges but when the electrons flow inside the diode ...
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Diodes normal polarised with voltage below forward voltage

Assume we have a circuit with a diode and a voltage source . The voltage source has potential 0.4V .If we polarise forward the diode ( p type region connected to cathode and n type region connected to ...
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Why does applying a voltage through the gate on a transistor help lower the potential barrier?

At the potential barrier, all that atoms are "satisfied"; they each have the appropriate number of electrons in their valence shell since the free electrons on the n-type side fill the holes on the p-...
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Reverse breakdown

What happens to a PN junction after the biasing voltage reaches the reverse breakdown voltage ?That is what exactly happens to that immobile majority charge Carriers ?Do they also contribute to the ...
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22 views

Diffusion current and depletion region with doping

I've been told that depletion region width decreases when we increase doping in a P-N junction. But doesn't this contradicts the fact that diffusion current increases with current? I'm probably mixing ...
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Metal Oxide Semiconductor (MOS) Capacitor strong inversion

Why the electron bands in the Body of the MOS capacitor do not bend much futher after the threshold voltage is applied? What stops them from doing it? For reference Modern Semiconductor Devices for IC ...
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Drude model for diodes

Well I was wondering how we can apply the drude model for diodes.The normal drude model is used on conductors and insulators and since the diode in forward bias is a good conductor(not the best but no ...
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The difference between optical phonons and acoustic phonons in terms of energy absorption

Why can the energy of a photon be directly absorbed by an optical phonon but not by an acoustic phonon?
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How do you calculate the electric field from conduction and/or valence band energy?

I am currently using a program to calculate the band diagram of a semiconductor structure in 3D. I am wondering if its possible to use the finite difference method to calculate the electric field. ...
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Low energy electrons occupy holes

In Tipler's Physics it is said that for a temperature $T>0$ the only electrons that can gain energy from collisions are the ones with initial energy greater than $E_F-K_BT$. I understand that, ...
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Diodes reverse bias to zero bias

Let's assume we have a diode and a battery.We connect the positive terminal of the battery(cathode) to the n-type region of the diode and the negative terminal of the battery(anode) to the p-type ...
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1answer
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How can electrons travel from the valence band into the conduction band?

I'm currently studying Introductory Semiconductor Device Physics by Parker. In band-theory, we know that if an electron is at the top of an energy band, then there are no allowed states immediately ...
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Why is silicon a good dopant for GaAs?

I have been looking into how GaAs and InGaAs quantum dots can be doped to make them negatively charged and I've found that they are doped will silicon. However, I'm struggling to understand why ...
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1answer
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Does doped semiconductor have free electrons at 0K?

For intrinsic semiconductors, they don't have any free electrons at conduction band at 0k and behave like insulators. But if doped, let's say n-type doped, they will have extra electrons which do not ...
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Is semiconductor wafer neutral after ion implantation?

If ions are implanted in a silicon wafer as the term 'ion implantation' suggests, how can the wafer be electrically neutral after the semiconductor doping? Aren't the ions ions electrically charged? ...
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Figure Description of Equilibrium in a Crystal Lattice

I am reading an Introductory Semiconductor Physics by Parker. The textbook states the following: The ionic crystal itself is formed by the ions coming together in an equilibrium configuration. ...
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Photovoltaic cell as an instrument for measuring intensity of light

I teach a lab in which my students measure the transmission of light through polarizing films oriented at an angle with respect to one another. To measure the intensity of the light, we use a silicon ...
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Forward bias semiconductors

Well I have done my research (click me! about reverse bias and I have understood it pretty well.What I dont understand is why dont we apply the same rule for forward bias as well.For example if you ...
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Can anyone help me to clear some questions about diodes and transistors?

i don't understand the basic of the working of diodes, because i imagine that if we have a n-p junction and we want to pass current through from side of n region to p region, if we beat the potencial ...
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Why don't electrons build up opposite electric field in a semiconductor diode in open switch mode?

I understand that during the closed switch mode the opposite electric field gets wider, but i don't see the reason when in open switch mode when electrons beat the opposite p-n field (0,3-0,8 volts), ...
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Why Li is not added as contact by ion implantation method in p type HPGe detector? [duplicate]

n+ contact of p type Ge is ~700µm thick compared to p+ contact of n type Ge only ~0.3µm. The process of adding the contact is different. n+ contact Li is added by diffusion process but p+ contact B is ...
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An ohmic contact

It is claimed that Schottky type of contact between low work function p-type semiconductor and higher work function metal creates an ohmic contact in which current can flow both sides almost fluently ...
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Why do semiconductor lasers become weaker after extended use (not due to battery)?

Why do semiconductor lasers become less bright as they are used for longer periods of time (assuming their battery is full)? Does it have something to do with the PN junction reaching some kind of ...
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Quantum tunneling in zener diodes

Well Zener diodes operate as a voltage regulator because of the Zener effect-Quantum tunneling . Quantum tunneling is the effect when an electron faces an energy barrier but after the energy barrier ...
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Why does the space charge in the depletion region in a pn-junction not create an electric field in the neutral region?

The majority carrier conduction electrons in the n-region of a pn-junction are closer to the the positively charged donor ions than the negatively charged acceptor ions in the p-region. The situation ...
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33 views

What is the density of states $SiO_2$?

We build the model by the finite element method. In our model here is silicon dioxide (SiO2). To carry out calculations, it is necessary to know the density of states and the effective mass. Question:...
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1answer
34 views

Under which condition the drift velocity stops increasing proportionally with respect to the electric field

Our professor asked us a question the other day but i wasn't able to figure it out. If we increasing Electric field then drift velocity will increase, Because of this Equation: Vd = μ * E But at ...
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Why and how do holes in the valence band of the p-type material of a p-n junction diffuse through to the valence band of the n-type material

tl;dr -- See the question title I quote from this Wikipedia article on the depletion region: By definition, the N-type semiconductor has an excess of free electrons (in the conduction band) ...
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1answer
36 views

Ion Implantation

I have a very basic question regarding ion plantation: when Silicon is doped with Boron, for example, it is doped by Boron atoms (3 valent electrons). When it is doped with phosphorus, for example, it ...
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Semiconductors with low thermal conductivity (lattice matched to GaAs)

What are the semiconductors with lowest thermal conductivity that can be grown on GaAs with the least possible incorporated strain (i.e. lattice-matched or close to it)? GaAs has thermal conductivity ...
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Can I consider electron scattering with grain boundaries in metal as a tunneling process?

I am reading about the Mayadas-Shatzkes model (MS model). when electrons are scattered with the grain boundary, there is a probability that it will be transmitted to the other side of the grain ...
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Quantum tunneling requirements

Why does quantum tunneling require a narrow potential barrier? I mean what makes zener diodes so unique is that they dont undergo heating because their potential barrier is very narrow.
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1answer
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Electric fields and electric potentials in semiconductors

The zener diode is heavilier doped than a normal diode , that is why its depletion region is smaller than the delpetion region of a normal diode and that is why the electric field is very strong.Zener ...
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2answers
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Why does the p-region have a higher energy level than the n-region in a diode?

Looking at the image below, I'm curious as to why the p-type region is at a higher energy level than the n-type region when no external voltage is applied. How is that? The E-field, if I'm not ...
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Zener diode electric field working principle

Well I recently saw a video from khan academy about zener diodes.This video was suggested by another member of Stack Exchange Physics who I thank him very much . But I didnt understand some things:...
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1answer
30 views

Chemical bond in diodes

Well I have seen diodes with many breakdown voltages. How is this possible ? I mean when an electron fills a boron hole it a bond is created between the boron atom and the nearby silicon atom.Well in ...
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2answers
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Will the electron-hole pairs in a solar cell ever run out?

I have read from various sources that, the photon strikes the solar cell and creates and electron hole pair which then migrates to their respective ends of the cells, this creates a potential ...
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Compensation Doping (Doping with 2+ elements)

In my microelectronics class we are talking about doping transistors. We learned how to calculate carrier concentrations for basic situations when we are doping a piece of silicon with one element. ...
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why in intrinsic semiconductor positive Silicon atom is known as hole but in extrinsic semiconductor positive Phosphorus is immobile ion? [closed]

why in intrinsic semiconductor positive Silicon atom is known as hole but in extrinsic semiconductor positive Phosphorus is not hole
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Why do electrons move towards a vacant position (hole) in a crystal lattice?

Why do electrons in a crystal lattice move towards the vacant position? Aren't electrons stable in their current position?
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3answers
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Question about full wave bridge rectifier

Sorry if this is a stupid question, what I know is when a diode is forward biased, it conducts current, when it is reverse biased, it acts as an open branch if its $ PIV \geq V_{in}$ But in this ...
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Why does nMOS using N+ gate have lower Vth than nMOS using P+ gate ? (w/o band diagram)

I understand it from band diagram.(Band bending is more stiff in N+ gate case) However, I don't know what's essentially happening. If P+ gate and N+ gate have same dose, their poly depetion will be ...
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2answers
67 views

Difference between diode and LED

What is the difference between a diode and a led? I know a led is a diode and I know how they are used and so on but I'm not really sure why a regular is not also light emitting. Therefore, what is ...
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1answer
26 views

Resolve The Envelope Detector Circuit

I was working on a little project and I was wondering if the envelope detector circuit could be resolved analytically. Let me explain. The circuit is the one shown above, I know the values of $C$, $R$...
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Types of effective masses

I understand the existence of effective mass for electrons, light hole, heavy hole, and split-off. But how can they be different from the density of states effective mass of conduction and valence ...
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1answer
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Gamma spectrometry: effect on one peak when adding another source

Suppose I have a sample containing only 137Cs. Now assume it shows 1000 cps counts for 137Cs, 662keV energy. Now I added 60Co (1173, 1332 keV) source in the same sample. Compton scattering ...