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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What sort of math deals with thermodynamics inside of semiconductors?

That is to say, how would one consider the thermodynamics of a complex chip like a modern CPU? I hear that designing the thermal efficiency of such systems is very difficult. I'm not sure why, ...
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71 views

Electron-Hole Spin Exchange Interaction

I am stuck with this seemingly "simple" Hamiltonian. I am dealing with an exchange term of a Hamiltonian for two different spin species: $$H_\text{exchange} = - \lambda J \cdot S = ...
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126 views

Internal Resistor in a Diode

When we talk about the resistance of a diode (of the P and N region), is this resistance like the one inside an Electro-Motive Force or it acts like a normal resistor (external electric field exist)? ...
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Definition of a semiconductor

Originally I had learned that solids are split into two categories: isolators/semiconductors, and metals. The fundamental difference between the two is the existence of a bandgap. Metals don't have ...
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117 views

Diffusion current and resistance of a diode

In a diode, there is a resistance in the p and n region, and electric field is required to move the charges in forward bias conditions. My question is: when there is diffusion current is the electric ...
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63 views

What is the difference between the Franz-Keldysh effect and free carrier absorption?

What is the difference between the Franz-Keldysh effect and free carrier absorption? My first guess to this is that the Franz-Keldysh effect involves a bandgap potential of non-zero volts D.C. while ...
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119 views

Semiconductor intrinsic carrier concentration is given by ni=BT^(3/2)*exp(-E/2kT), how is this derived?

The glorious book Sedra/Smith Microelectronic Circuits states that for a semiconductor the intrinsic charge concentration is is given by: $$ n_i = BT^{3/2}e^{-E_g/2kT} $$ Where $n_i$ is the ...
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73 views

Does reverse biasing hold any meaning in case if both terminals are n type semiconductors?

When we talk about an n-p-n transistor in common emitter configuration, we often say that emitter-collector circuit (the one towards right) is reverse biased. In what sense it is reverse biased? Here, ...
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191 views

Don't electrons have discrete energy levels in semiconductors?

I am having a hard time understanding the relation between the fermi distribution of electrons in a semiconductor, and the fact the electron energy states are discrete. The fermi distribution is ...
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selection of p substrate as wafer in typical cmos process flow

why is p-substrate typically used as wafer in the typical cmos process flow? why not n substrate?with respect to memories, Has it got anything to do with the aplha-paritcle radiation induced errors ...
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341 views

Why can solar cells be made of indirect and direct semiconductors? (Comparison between some pn-junction devices)

Various textbooks mention, but not go into detail, how semiconductor devices are optimized for their particular function. E-k space is trascendental to understand this, given that it depends on the ...
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397 views

Can the Fermi level go above the conduction band energy if doped heavily enough?

So for n-type Si with donor density $N_d$ and donor energy level $E_d$, $N_d^+ = N_d(1+\frac{1}{1+e^{\beta (E_d - E_f)}/2})$ is the number of ionized donors, so we get an relation between the number ...
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Cryogenic Conductivity of a Defective Semiconductor

If I have a semiconductor with a lot of defects what happens to its conductivity at at mK type temperatures? I'm expecting that defects would give rise to greater conductivity than for a perfect ...
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97 views

How is periodic potential approximation justified in semiconductor physics?

In semiconductor physics the usual approximation is that of infinite crystal. This seems to allow one to write Hamiltonian for electron subsystem (in adiabatic approximation) as having periodic ...
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42 views

Literature on semiconductor modeling

Analysis and Simulation of Semiconductor Devices by Selberherr (Amazon link) seems to be the book on the basics of the craft, yet it was written in 1984. Are there any more recent books or have the ...
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114 views

Increasing the efficiency of photovoltaic power cells

Given that solar cells use one or more semiconductor materials to convert light to electricity, and that the efficiency of that conversion is dependent on the material and the wavelength of the light, ...
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36 views

Why are generally two of three effective masses identical?

In indirect semiconductors, the effective mass of electrons depend on the direction. There are three principle directions pointing away from the global energetic minimum in which the effective masses ...
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211 views

Confusion about depletion layer in pn-junction?

Here: external link Seek: around (2:53) Since n-type and more electrons than p-type and vice versa for holes, they diffuse and in the process neutralize in the central region. How is the ...
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34 views

Doped Semiconductor and jump of electrons

This confuses me: In the wikipedia article it talks about how the majority charge carrier is electrons for an N-type semiconductor How come the electrons in the conduction band don't just jump into ...
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74 views

Resistance of a diode in different regime and the physics of recombination current

I would like to ask question about the resistance of a diode under different regime. Surely, in reverse bias, it has a breakdown voltage, and in forward bias,it rises exponentially according to the ...
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124 views

inability of indirect gap semiconductors to emit light efficiently

what is reason of inability of indirect gap semiconductors to emit light efficiently?
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Why organic materials' hole mobility is usually higher than electron mobility?

Most of OFETs, and in particular OTFTs, are p-type (p-channel devices), because the hole mobility is higher than the electron mobility in most organic materials (wikipedia). What is the reason for ...
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What does Fermi level in the band gap mean?

What does it mean that the Fermi level for some semiconductors lie in the band gap? Is Fermi level definition different from what is know as usual? We define the Fermi level as the highest level of ...
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207 views

Does doping silicon affect its coefficient of thermal expansion (CTE)?

Everywhere I have searched I always see the CTE of silicon listed as 2.6*10e-6 °C^-1. However, I have silicon that was phosphorus-doped to an ion concentration of of 2.41*10e11 atmos/cm^3, and I would ...
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Ohmic contacts in a diode (metal-semiconductor junction) - contact difference of potential $V_0$ - how to compute

I'm reading "Microelectronics" by Millman, Grabel. Premise: The book developed, for a pn step-graded junction, the contact potential as $$ V_0 = V_T \text{ln} \frac{p_{p0}}{p_{n0}} = - V_T ...
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Electric Field inside a diode

When a voltage is applied to a diode (Forward or Reversed bias) the depletion zone is changed due to charges change in this region. My question is in both case (Forward or Reversed bias), how the ...
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133 views

Is the built-in potential in a PN junction the same as the “knee” or “turn-on” potential?

Considering a PN junction with a difference in fermi level between the P and N type regions given by eV0. Does this V0 correspond to the potential at which the diode "switches on"? My intuition tells ...
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242 views

How is the bandgap reference diode so accurate? (temperature changes bandgap?)

I am studying about bandgap references (wiki). As a black box approach, (from what I know) it can be seen as a system which gives a stable voltage reference irrespective of the highly varying ...
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Topology of a bit

From a math perspective, it seems obvious that the electric field (or voltage which ever) of a bit in a computer, when its in a stable 0, or 1 state, must have a singularity, a set of points where the ...
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331 views

What limits the doping concentration in a semiconductor?

Si and Ge can be blended in any ratio, $\mathrm{Si}_x\mathrm{Ge}_{1-x},\ 0\le x\le 1$. So do InxGa1-x. So what exactly causes doping impurities inside Si/Ge/etc. to saturate at $\sim 10^{-19}\ ...
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Can a strained diamond actually become conductive?

According to about.com, "The electrical resistivity of most diamonds is on the order of 1011 to 1018 Ω·m" (source) However, according to the diamond band diagram, it seems that under a certain ...
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302 views

Graded semiconductors - hole concentration function of x

I'm stuck at page 37 of the (second ed.) of "Microelectronics" by Millman & Grabel, section "1-7 Graded Semiconductors". Before that section, it spent some time explaining the phenomenon of ...
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102 views

Semiconductors and energy bands

The valence and conduction band of a semi-conductor are often drawn as here click. This plot has essentially two features and I would like to understand them. The peak and the valley of the two ...
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3D Density of states

I have the following dispersion relation: $$\epsilon(\vec{k})=\frac{\hbar}{2}\left(\frac{k_x^2}{m_1}+\frac{k_y^2}{m_2}-\frac{k_z^2}{m_3}\right)$$ (note the minus sign in the third term). And I am ...
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Periodic momentum space in band structure

I often see pictures like this in physics, this one for Silicon band structure. (source, NB: it's the German page for Silicon). There you see the plot of the energy in terms of the momentum $k$. ...
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Hole, solid state physics

In n-type semi conductor, when hole is created, which starts to move, but not in p-type semi conductor, hence, is a hole a static or dynamic? hole is absence on electron, absence means nothing, then, ...
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Exciton in semi-conductor

I don't understand why an exciton describes only the interaction between an electron hole and an electron in the conduction band? How is this interaction different from the interaction between an ...
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168 views

Why are laser pulses Sech Squared in temporal shape?

Ultrashort pulses from mode-locked lasers often have a temporal shape which can be described with a squared hyperbolic secant ($\mathrm{sech}^2$) function: $$ P(t)=P_0 \mathrm{sech}^2 \left( ...
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Why an undoped heterojunction causes potential barrier?

In this image (source) a potential double-barrier was created using GaAs and AlAs lattices (undoped). Why would any potential barrier be formed, if all the bonds are electrostatically balanced (i.e. ...
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Why the current through a resonant tunnel diode drops when the bound state goes below the conduction band?

The IV curve of a resonant tunneling diode is N-shaped. The rise in current flow happens because the bound state (the energy state in the well) enters the thermal area of the conductor ($\mu_1 + ...
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Why a tunnel diode (TD) is called a diode?

Traditionally, a diode is a 2-terminal device that limits current to flow in one direction, i.e. a rectifier. But a "tunnel diode", according to wikipedia, is not rectifying: In the tunnel diode, ...
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Why do silicon solar cells only produce ~0.6V when the band gap of silicon is ~1.1V?

I've been researching into this and can't quite figure out where that lost voltage is going. When silicon is excited by a photon within its absorption spectrum, it will always have an internal ...
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295 views

Crystal structure of Silicon

From what I was reading, Silicon has a FCC unit cell but they also said that the Silicon atoms form a tetrahedron at 109 degrees from each other. Then they said that the tetrahedron is formed by ...
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451 views

Lattice and carrier temperature

If I hold a semiconductor sample at a certain temperature $T$, its lattice temperature $T_l$ will equalize: $T_l=T$. But how is this lattice temperature related to the carrier (electron or hole) ...
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485 views

Question on Shockley's equation for FETs

I'm currently studying FETs (Field Effect Transistors) in Navy school. What I know so far is that in FETs, $V_{gs}$ is reversed biased, creating a depletion zone. What this means in plain English is ...
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114 views

Why don't electrons simply diffuse back when illuminating a photodiode?

Assuming you connect the cathode and the anode with a conductor (no sources), why can't the electron-hole pairs created by the photons diffuse back instead of going through the wire? My reasoning is ...
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Couting the occupied states in band structure

I work with several dft codes and I have produced the band structures of some doped semiconductors with their plots. The problem I have is that I do not know how I can analyze the band structure and ...
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A question about Memristors

A question about memristors: These semiconductor entities have been defined in terms of magnetic flux leakage, and a non-linear relationship to the electric charge that has flowed. In essence, the ...
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What makes Monocrystalline silicon a good semi-conductor? [closed]

I'm researching Monocrystalline silicon for a school project and focusing on its application in Electronics. One area I'm researching is why the material is a good semiconductor, and what properties ...
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Why is the heavy/light hole band not called heavy/light electron band?

Are the bands called heavy hole, light hole and electron band, just because the charge carriers are holes/electrons or is there some deeper reason I missed? The question might seem stupid, but it ...