What is Semiconductor: Definition and 397 Discussions
A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions and electron holes, at these junctions is the basis of diodes, transistors and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
Semiconductor devices can display a range of useful properties, such as passing current more easily in one direction than the other, showing variable resistance, and sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion.
The conductivity of silicon is increased by adding a small amount (of the order of 1 in 108) of pentavalent (antimony, phosphorus, or arsenic) or trivalent (boron, gallium, indium) atoms. This process is known as doping and the resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to the behavior of a metal in which conductivity decreases with an increase in temperature.
The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping greatly increases the number of charge carriers within the crystal. When a doped semiconductor contains free holes it is called "p-type", and when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for the useful electronic behavior. Using a hot-point probe, one can determine quickly whether a semiconductor sample is p- or n-type.Some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to the invention of the transistor in 1947, the integrated circuit in 1958, and the MOSFET (metal–oxide–semiconductor field-effect transistor) in 1959.
Homework Statement
Determine values for beta the constant of proportionality for a semiconductor.
Homework Equations
Given below.
The Attempt at a Solution
Im struggling with line 2 to line 3 of the solution. The problem I'm having is I can't see where the squared exponential term has...
Homework Statement
we look at a silicum n++ p+ n transistor. given:
NE= 1,0×1018 cm–3;
NB= 2,0×1016 cm–3;
NC = 2,0×1015 cm–3;
here E stands for the emitter, B for the basis and C for the collectorHomework Equations
a. calculate the distance in eV from the fermi-level to EFi for the emitter...
Taken from my textbook:
My understanding is that:
One valence electron, 2 spin states -> Half-filled Brillouin zone
Seeking inspiration from "Nearly Free Electron Model": gaps open up at zone boundaries
States nearer to zone boundaries get pushed down in energy further
Since a fermi...
I have calculated the electron transmission function T(E) over a potential step of height V0 using T-matrices. I model a semiconductor heterojunction, which requires different effective electron masses on either side of the step.
The wave functions on either side of the step are planar waves...
From some literature, I read the following band structure of the Al doped Si.
The explanation offered: "have vacant acceptor levels at energy Ea above the valence band. Electrons from the top of the valence band can be easily excited into these levels."
I thought the above explanation is...
I have calculated the electron transmission function T(E) over a potential step using T-matrices. I model a semiconductor heterojunction, which requires different effective electron masses on either side of the step.
We have 2 boundary conditions at the step at x = x0:
Y1(x0) = Y2(x0)...
As the atoms of a material are brought closer together to form the crystal lattice structure, there is an interaction between atoms, which will result in the electrons of a particular shell of an atom having slightly different energy levels from electrons in the same orbit of an adjoining atom...
What are the commonly asked questions for the semiconductor process engineer position ?
I am assuming cleanroom equipment working principles.. what else?
Thanks in advance for your responses.
Hello everyone,
I have a quick question about the energy of the silicon. I know that, as a semiconductor, the silicon has an energy gap between the valence band and the conduction band. But according to this image ...
Hello.
I'm currently taking a physics course that gives me the freedom to take any subject related to semiconductors and do some research on it, presenting it at the end of the semester. I know I want to do something related to programming, but I'm having a hard time finding a theme. Hence me...
Why is black phosphorus a semiconductor with a direct bandgap?
The problem is mentioned by the two following references:
"The three bonds take up all three valence electrons of phosphorus,so, unlike graphene, monolayer black phosphorus is a semiconductor with a predicted direct bandgap of 2 eV...
I'm trying to understand how a diode works and for this I've used(among other resources) the book written by Albert Malvino, Electronic Principles.
Everywhere I read about this topic, it says that when the N-type and P-type semiconductors are joined together, the free electrons from the N-type...
I understand the difference between p-type and n-type semiconductors but I just don't understand how adding a
p-n junction to a circuit affects it.
Can someone please explain how semiconductors work?
For example, if I had a circuit with just a battery and a light bulb, what would change if I...
When electrons leave the valence band and jump over the gap to the conduction band, what is the density of the remaining holes?
If 2.5 electrons/cm^3 leave the VB to the CB, will the density of remaining holes be 2.5 electrons/cm^3?
To me it is logical, but I am wondering if mass of electron...
I've been playing around with some ideas of electron-hole pairs in semiconductors lately, have realized that I'm confused about some basic conventions that maybe the physics forum community could help clear up.
Let's imagine that we have a direct gap semiconductor initially at zero temperature...
http://physics.stackexchange.com/questions/156708/can-the-relative-permittivity-of-a-semiconductor-material-be-lower-than-1
To measure the relative permittivity of a p-type semiconductor material (a metal phthalocyanine ) , a M-S-M structure was made by thermal evaporation method. The...
Given a material sample, what are the different experiments that one can perform on it to check if it's a conductor or a semiconductor. For eg, we can measure R at different temperatures. Anything else we can do?
How conductivity increases in n type semiconductor as ni^2 (formula nh multiplied by ne=ni^2 where nh=number of holes per unit volume and ne=number of free electrons per unit volume and ni=number of intrinsic charge carrier per unit volume remain constant?What is the use of increased number of...
I plotted n type carrier density vs temperature plot at zero applied bias and the intrinsic carriers dominate the extrinsic carriers at high temperature, now I wonder how plot changes if I apply positive bias to this semiconductor. Does intrinsic carriers dominate the others at lower temperature?
Hi Guys, i need your help, where can i download free articles about the band gap of semiconductor materials (like copper (II) oxide). don't mention sciencedirect and arxiv, because i already explore that, and they provide limited research articles. thank you.
What exactly is conduction band?electrons from valence band jump into conduction band where they exactly go ,do they go to higher shell or subshell or orbital or stays in same place with more kinetic energy?
I'm very new to semiconductors. I want to do basic calculations. How would I go about calculating and graphing the energy of the electrons and holes given the magnetic field and the state.
Also, how would I do the same for the electron and hole population.
I'm looking to buy a semiconductor cross reference book, for part numbers and diode and transistor parameters, including new smt parts. I had an old sgs Thomson book but it got lost in a move, if anyone could recommend me one that would be great.
I don't want a link to a website cross...
I've been doing a bit of reading on bandgaps of semiconductors and alloys of semiconductors. I was curious to know is the bandgap of a material, say Silicon, determined or calculated experimentally? How do scientists usually determine this in the lab?
Homework Statement
Homework Equations
Shown in question.
The Attempt at a Solution
So I was given this question for homework and I'm really not sure where to start. I'm not looking for somebody to do my homework for me, just somebody to point me in the right direction. The...
I have joined a research lab on semiconductor nano devices and have been recommended to study the Robert F. Pierret book "Fundamentals of Semiconductor Devices" but unfortunately I could not understand most of the concepts after reading first three chapters. I am a computer science graduate with...
If you research the materials semiconductors are made of you will find things such as aluminum gallium arsenide. How do you determine what the p-type and n-type are made of? Shouldn't there be a structural difference in order to create band gap?
I am getting an opportunity to do PhD in semiconductor devices. The professor is quite active in the field and publishing good research. I have no background in solid state physics. How difficult it could be with a computer science background? Also where should I start once enrolled in a...
Hi Guys, I read that the Fermi level of semiconductor, like germanium, is in-between the completely occupied upper band and conduction band, i.e. right in the gap. Why is that? shouldn't it have beed exactly the highest occupied level ?
Hi all,
I have a question and ask for a discussion. Can the pumping current of the semiconductor lasers such as DFB laser and FP-LD, be smaller than zero?
Best Regards,
Jason.galq
A new type of energy storage described which uses quantum way to store energy.
''Battenice''.
http://techon.nikkeibp.co.jp/english/NEWS_EN/20140224/335902/
How exactly new energy levels could form under UV light? What do the mean?
please see attached image for problem
if a dopant gives an electron it's an n-type, if a dopant takes an electron it's a p-type.
i can't see how to relate the hall coefficient value to the property of being a n-type or p-type semiconductor?
any pointers on this would really be...
I'm trying to understand the form of the absorption spectrum of a T=0K intrinsic semiconductor. The valence band/conduction band energy diagram looks like;
http://postimg.org/image/wyzvo9lsr/
As E = \frac{\hbar^2 k^2}{2m^*}
where m^* denotes the effective mass. The image doesn't...
Homework Statement
Estimate the electrical conductivity, at 135°C, of silicon that has been doped with 3 x 1024 per meter cubed of aluminum atoms. Assume values for electron and hole mobilities of 0.03 and 0.007 m2/V-s, respectively.
Homework Equations
σ=|e|(ne*μe+nh*μh)...
My question is about drift and diffusion current.In a semiconductor diode no "bias" condition diffusion is present and due to transfer of charges due to diffusion depletion region created and then this region has ions which produce electric field which results in drift current due to force the...
Homework Statement
The current-voltage characteristic curve of a semiconductor diode as a function of temperature T is given by the equation: ##I = I_0(e^{|e|\Delta V / k_BT}-1)##
where e is the base of the natural logarithm.
|e| is the charge of an electron
k_B is the boltzmann's...
I don't know if I am asking some stupid questions but I can't really move without knowing them.
(1) In reverse bias situation electrons attracted towards positive terminal and hole attracted towards negative terminal widen the depletion region .My question is that why can't these hole...
Homework Statement
Here is the problem in the book:
Here is the solution:
What I don't get is why the solution defines the fraction to be ni/(5*1022). Shouldn't it be 2*ni/(5*1022) since we have both donors and acceptors, so there are actually twice the number of atoms.
Also...
I'm aware that you "dope" them with phosphorous for n-type and boron for p-type (I'm aware other materials can be used and other dopants are preferred in other situations). My question is exactly how is this done? Temperature, Pressure, Sputtering, etc.A white paper or something of the exact...
The question asks for a pn junction, calculate the total bending through energy at zero bias of the conduction band edge passing from neutral n-type section to the neutral p-type section.
Additional info:
Band gap of silicon Eg = 1.1 eV
Density of states at conduction band (Nc) = 2.8e19...
Hi,
I am looking for a good book or any other online resource on semiconductor physics. What I need the book to cover is:
The PN junction i.e. the diode
BJT transistors
MOSFETS
In particullar I am interested in the derivation of the equations of the above components, the Shockley...
hey guys i just wanted to confirm something;
so, for systems of continuous energy states (or small separations of discrete energy states), we can plot a graph like this and call the fermi energy the middle point where Probability=1/2. like this
where, if T=0K, the transition from...
I understood that the fermi level is a hypothetical energy level given by the Fermi-Dirac distribution where the probability of finding an electron is exactly 50%. My question is: it always takes (Ec-Ev) energy to excite the electrons in the conduction band in an intrinsic semiconductor or...