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34

The reason is very simple. Computers depend on electronics. Even the first diodes and triodes that the first bulky computers were made up of depend on the quantum mechanical nature of matter. The present ones with the chip technology are directly dependent on energy levels and bands of conduction etc in the electronics used. Semiconductivity is a quantum ...


19

Yes. That is the operating principle of this device, among many others:


17

I find this quite an imprecise catch phrase. It's as correct as saying with out quantum mechanics there would be no atoms because electrons would have fall onto nuclei. There would be computers but not like the modern ones. The first (electrical) ones didn't depend on quantum mechanical effects, they used vacuum tubes in place of transitors. Not to mention ...


11

Any good book in Semiconductor Physics will have a description of the k.p method. Try Fundamentals of Semiconductor Physics by Peter Yu and Manuel Cardona. Another reference for Kane Model and EFA are chapters 2 and 3 of "Wave Mechanics Applied to Semiconductor Heterostructures" by Gerald Bastard. If you want a more mathematically/group theory oriented ...


9

As an engineer, I've had to get pricing on stuff I wasn't going to buy many times in the past. I doubt you'll find a website which will have the prices, but you can find them yourself in a few hours work. What you do is this: Call them up and ask for a "sales rep" (abbreviation for "sales representative" but nobody calls them by the full name) tell him/her ...


9

You might find the Yahoo "home_transistor" group a useful resource. There's also a series of videos on YouTube by Jeri Ellsworth including some where she makes transistors. In one, in particular, she takes the crystal out of a germanium point-contact diode and turns the crystal into a point-contact transistor (much like the Bell Labs transistor.) There ...


9

The absence of a material in a volume embedded into a larger volume that is fully filled by the material is always known as the hole. For example, look at this hole in soil. In semiconductors, the "soil" is replaced by the semiconductor material itself, with the right number of electrons per nucleus to make it neutral. So if there is an electron missing ...


8

Quantum mechanics led to a deeper understanding of field electron emission which was instrumental in developing the theory of electron energy bands and, in particular, an appreciation of the band gap. This let us work out the physics of semiconductors and develop models for selecting and refining semiconductor materials and treatments.


8

In calculating the electron dispersion you probably obtained the diagonalized Hamiltonian in the momentum space $$ H=\sum_\mathbf{k}\left[c^{\dagger}_{\mathbf{k}A},c^{\dagger}_{\mathbf{k}B}\right]\left[\begin{array}{cc}0 & \Delta(\mathbf{k})\\ \Delta^{\dagger}(\mathbf{k}) &0\end{array}\right]\left[\begin{array}{c}c_{\mathbf{k}A} \\ ...


8

Yes, your interpretation heuristically makes sense. As you may already know, as a consequence of Heisenberg's uncertainty principle, that an electron has a wave and particle nature. When you think of the wave nature of single particle states you are talking about Bloch states. When you're thinking about the particle nature you are talking about Wannier ...


8

The notion of a particle in nonrelativistic quantum mechanics is very general: anything that can have a wavefunction, a probability amplitude for being at different locations, is a particle. In a metal, electrons and their associated elastic lattice deformation clouds travel as a particle. These effective electron-like negative carriers are electron ...


7

A diode consists of two materials known as p-type and n-type semiconductors, connected in series which allows current to flow through them differently. In the n-type semiconductor, electrons travel with enough energy such that they're not attached to an atom and are said to be in the conduction energy band. For the p-type semiconductor, electrons "hop" from ...


7

The argument is not a mathematical Taylor expansion, there is an implicit physical argument here which is very well known but not given. The rate of a reaction (like recombination) at low density should be the product of the densities, with a coefficient that is independent of the density. This happens to be a mathematical Taylor expansion in the densities. ...


6

The moore's (empirical) "law" states that the number of transistors in a chip increases exponentially (doubles every 2 years). So the question is : is there a hard limit in the number of transistors in a chip? Or, in other words : Are there limits on the size of a chip and on the size of transistors? Indeed there are (almost). The matter is made of atoms, ...


5

The key difference between a Zener diode and a normal diode is that the Zener diode has a low breakdown voltage - typically in the few volts range. The breakdown voltage is low because the heavy doping means the depletion layer is very thin, and even at a low voltage the field strength over this thin depletion layer is very high. With a conventional diode ...


5

It's difficult to know for sure without having access to the Thouless paper that you mentioned. However, in my own research field we sometimes talk about two processes called tunnelling and hopping, that are distinguished as follows. Tunnelling is a coherent process in which electrons move from one lattice site to another, maintaining a definite phase ...


5

Think about why the diode does conduct current when it is forward-biased. In that case, there is an electric field pointing from the P-type end to the N-type end. Negative electrons want to climb up the field. The electrons get to the junction and find holes to fall into. Now that the electrons are in the P-type material they can find their way to the ...


5

The ${\rm sech}$ pulse is, in Kerr effect nonlinear optical mediums, an Optical Soliton. This means that it is the particular time variation such that the tendency of the pulse to spread out in time owing to linear dispersion is exactly counterbalanced by the nonlinear effect that tends to confine pulses in time. This balance is a stable one in a Kerr ...


4

I've heard this in many quantum mechanics talks and lectures, nevertheless I don't seem to grasp the idea behind it. There is no “idea” behind it. Just general fluff talk, like saying we wouldn’t have the lightbulb without Ohm’s Law (Fact: Lightbulbs were in existence before Ohm formalised his law, and the first practical Swan-Edison bulbs had one ...


4

The key word that makes the statement approximately true is "modern." There are many computing devices that can be (and have been) created using pre-transistor parts. Pascal and Leibniz constructed adding devices with gears. Babbage designed (but did not build) a programmable computer with gears, linkages and metal plates with holes in them. Completely ...


4

We can't see in the heads of committee members, but to understand the tradition of "what for what" in Nobel prizes, I think it is instructive to see the chain of Nobel prizes awarded for developments connected to nuclear magnetic resonance (NMR). Here's a list. There were three prizes in Physics during 1943-1952, two prizes in Chemistry during 1991-2002 ...


4

In an idealized semiconductor at absolute zero, all the valence states are occupied by electrons, and all the conduction states are empty. When you take one electron an place it into the conduction band, you leave behind a state that is no longer occupied in the valence band. Now, lets say you have a sample with a billion electons, all in the valence band, ...


4

From "The Transistor, A Semi-Conductor Triode", by J. Bardeen and W. H. Brattain, Phys Rev. 74(2), 230-231 (1948): "The device consists of three electrodes placed on a block of germanium as shown schematically in Fig. 1. Two, called the emitter and collector, are of the point-contact rectifier type and are placed in close proximity (separation ~0.005 to ...


4

Modern processors are built from CMOS technology. These digital circuits consume relatively little current when sitting in one state or the other. However, there is some inevitable capacitance on every node. When the output of a digital gate changes state, that capacitance is charged or discharged, which means current has to flow. The total average ...


4

"Equilibrium" means thermal equilibrium. The solid has one well defined temperature, and a constant Fermi energy. The Fermi energy is an energy value against which energy levels are compared to determine how fully occupied (or not) an energy level is. Generally when the Fermi level is constant throughout a solid electrons diffuse equally in all ...


4

The convention is that current flows in an electrical circuit from positive to negative. This was decided before electrons were discovered and before they were discovered to be negatively charged. You can identically consider the flow of electrical charge as either the movement of a negative electron from left to right, or the movement of the empty place ...


4

I was looking for a company who can provide Si (and potentially other) wafers of various types, and I can say the following: 1) You will have a hard time finding 'fixed' pricelist. Companies are not ready to quote you unless you are ready to buy XXX amount. 'I am just checking prices around' not gonna work. 2) Price is drastically different if you are ...


4

Determine = design or measure? A dark-ish room, a white piece of paper and a ruler should do for a bright LED. Modelling it accurately, especially if the LED has a plastic lens built-in and you don't know the precise details of the die position, is trickier. If the LED has a builtin lens then about the best you can do is just match the angle coming out of ...


4

Not really an expert on solid state physics, and I'm prepared to look an idiot here - but I don't think it's the low temperatures that help. By overclocking a CPU 5.5Ghz you are almost doubling the power consumption and hence the dissipation. A large reduction in the temperature of the cold site of the heat sink helps it remove twice as much power while ...



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