Quantum Wells - Science topic

I want to measure the electrons effective mass, concentration, and mobility in an AlAs/InGaAs quantum well on an InP substrate. Is there a book or guide on designing a Hall bar for such measurements?

My main uncertainties concern the following points:

I have found some papers on this topic, but they do not provide detailed fabrication procedures.

For reference, the epitaxial structure is as follows:

I am working on a project using Sentaurus TCAD to design a Silicon and Silicon-Germanium quantum well structure. Below is the physics configuration I have implemented:

Physics(Region = "R.emitterl1") {

HeteroInterface

}

physics(Region = "R.qbl1") {

HeteroInterface

Active(Type=QuantumWell)

QWLocal(

eDensityCorrection

hDensityCorrection

)

}

Physics(Region = "R.emitterl2") {

HeteroInterface

}

physics(Region = "R.qbl2") {

HeteroInterface

Active(Type=QuantumWell)

QWLocal(

eDensityCorrection

hDensityCorrection

)

}

Physics(Region = "R.emitterl3") {

HeteroInterface

}

I encounter the following error when selecting materials via the "include material" function:

Could you please assist me in resolving this issue? Specifically, I need guidance on:

Thank you in advance for your support. I appreciate any insights or documentation references that can help address this problem.

Best regards,

Yuan

I'm making quantum well with 2 different bandgap materials, but I'm not sure quantum confinement effect was occurred because the well width is ~ 60 nm.

How can I make sure that effect? Is there any technique or equipment (for example, PL) to measure quantume confinement?

Thank you.

Hello everyone ,

for a layered quantum well, does the addition of layers in the quantum well increases its depth.

What is the highest EQE ever achieved by a light-emitting diode containing a multiple quantum well structure? I'm looking for record values achieved for different colours / wavelength regions (red, green, blue, UV, IR).

I am trying to simulate a Single Quantum Well green LED using Silvaco. I want to see the effect of adding an insulator to the sidewall of the structure. However, when I do that, the current in I-V characteristics increases by 1 order of magnitude and I can observe a band bending in the insulator and the semiconductor. How do I resolve this issue to obtain a reasonable band diagram after adding insulator?

We have fabricated free-standing monolayer MoS2 (0.8 nm thickness). The surrounding medium(both side) are air (insulating in nature). The monolayer MoS2 has a band gap of 1.8 eV. It is a kind of double heterostructure condition.

Therefore, Is it correct to consider that a free-standing structure is a quantum well or not?

I would like to study the interaction of intense light with quantum wells and wires. I would appreciate it if you inform me which software you use.

Dear All,

I need experimental researches that explain the tradeoff between short circuit current and open circuit voltage when we increase the number of QW, or width.

Thanks in advance

What substrate should be used and what materials should be used for quantum well etc.

I am able to solve the Schrodinger Equation of AlGaAs-GaAs Single Quantum well for eigenvalue study. Please suggest how to simulate for Schrodinger-Poisson equation self consistently in COMSOL

I am trying to use k.p theory to calculate bandgap of range of nanowire diameters. Can someone show me any example file in Matlab or script in any other language? Also if someone can suggest book for the beginning user? 

I am looking for the deepest quantum well created by semiconductors bands offset in heterostructures. Would greatly appreciate any help!

I would like someone to guide me to simulate a quantum well solar cell based on SiGe / Si. If I find this silvaco code example it will really help me a lot

Hi.

I am trying to simulate a 10 QW hetero-structure in Silvaco Atlas. I am trying to extract the following parameters of the quantum wells -

If anybody has extracted above parameters from the simulations of MQW structure, then please let me the models in Silvaco which are useful.

Thanks

Hi ,

this is a basic question which came to mind..

Can we have the well material and the bulk(host) material same and different material for barrier ? If we have Type-1 band structure and lower bandgaps for well, higher bandgaps barriers, then will there be any real problem implementing this structure ? In text books/references, I find the barrier and the bulk material are same and different material for same.

Thanks

Prabhu

I was trying to build a quantum well structure using ATLAS TCAD where in barrier and well material need to be repeated many times, say 50 times. What I thought is defining a material for barrier and well, grouping them and repeating them through programming ( in lines of "for loop in HLL"). Is this idea possible Silvaco ? Please let me know if anybody has done similar work/code.

Thanks

Prabhu

Hello!

I'm trying to modulate the electron density in a thin layer of InGaAs highly doped (25nm, 1e19cm-3 n-doped) using field effect with a MOS-like structure, but for the moment, I can only change about 1e17cm-3 of the free electron density (Hall effect measurement) when I apply a +/-4V gate voltage.

Our computation using 1D-Poisson code '(Sneider's one) shows a much larger modulation (about 5e18cm-3). We are not sure what was not taken into account in the computation.

Is this feasible to modulate such large electron density? I'm searching in the literature but I haven't found any study about this. In MOS transistor I saw doping levels of 1e17cm-3 but not as high as what I'm studying.

Thanks!

N. LE-Tuan

I am writing a program for quantum well simulation. To increase the no. of wells i have come across a statement MQW in SILVACO ATLAS. If i use i am getting error or the simulation getting inturrepted. Can anyone please guide me through this.

The fact that , electron can have only discrete energy level is obtained by solving schrodinger equation with boundary conditions, which is a mathematical derivation .

Physically, What makes the electron possess only certain energies ?

Or is there any physical insight or explanation or physical intution which can arrive at same conclusion(without math) that electron can have only discrete energy levels inside potential well

In solar cell applications I need to model PN junction, In lumerical's FDTD we can create new material in material database, there we can make any material with desired np density (electron hole density), but after that my simulation diverges due to material gain I suppose. 

Dear all:

I am currently working on nanostructured solar cells simulation. I study analytically the impact of nanostructures such as quantum wells and quantum dots on solar cells, but I also want to learn about and use other free software to performe numerical simulations on nanostructured solar cells and for comparison. Please, in your experience can you recommend me any potential free sofware to performe numerical calculations on the impact of nanostructures on solar cells (in particular inorganic solar cells) based on quantum mechanics and semiconductor physics? Is it there any free of charge software or all are for paid? If so, please can you help me with links to access the sofware? How much does non-free software approximately cost? Thank you very much for your kind response in advance!

I am working on III Nitride multi-quantum well light-emitting diodes using Crosslight APSYS. Here I would like to extract the electron and hole wave functions, Can anyone please suggest how to extract it?

Thanks in advance.

Regards,

Ravi

I want to calculate the QWSC performance. The problem encountered is how to introduce the Quantum well in the structure . Can anyone suggest to me how can I simulate QWSC without any problem? Thank You!!

The development of quantum well solar cells QWSCs (Quantum Well Solar

Cells) has generated a great deal of interest. These configurations have shown good

promise to optimize the conversion efficiency of current solar cells because of the

high rate of absorption losses present in them.

I need a help in this point : How to introduce the quantum well in CIGS absorber part, using silvaco software?

I have read that, from broadening of the peak the existence of defects is realised. Is it right? If so, I want to know the reasons of broadening.

Formation of quantum well is a reason I have found. How quantum well is related to defects?

Thanks in advance.

I am trying to simulate the thermal resistance of an AlGaN/GaN based laser. Mainly, I want to see the temperature profile of the assymetric design of the paper in the attachment (Arafin et al 2019). The device consist of three quantum wells each having 20 nm thickness. Pumping 1.5 W of electrical power (10e16 W/m³), I see there is a temperature rise of around 14K. So the thermal resistance was found to be 9 K/W. Can anyone tell me what is the typical thermal resistance of this kind of devices? Thanks!

Dear frnds,

From my point of view SSB is happening due to following reasons in double quantum wells.

1. Due to variational technique

2. symmetry in envelop function and inherent asymmetry impurity wave function

3. self-consistent calculation of Coulomb interaction.

Kindly give reasons beyond this.

In addition to the width of the well, there is still planar size.

Among different shapes of well, which is the most suited well in terms of efficiency

Since quantum well lasers are made up with heterostructures is there any chance of a photon to be emitted with a different energy of the one related to the well bandgap? I mean the energy of the bandgap of the semiconductor without the well.

Dear Researchers,

What is the effective mass of electron and hole of In_xGa_1-xN and does the effective mass depends on the indium mole fraction x?

and Does it also depends on the thickness of the quantum well of InGaN in InGaN\GaN MQW structure?

Thank you.

I need to study the 14 band k.p model for which I need Heavy hole energy, Spin orbit Split off energy, coupling parameter of Al in AlGaAs/GaAs quantum well.

The MQW is (GaAs/AlAs) on GaAs substrate?

I getting a convergence problem while simulating InGaN/GaN multiple quantum well solar cell. How can I solve it?

Note: The problem occur when I add quantum well region, without quantum well region the code runs fine.

Also I have adjusted the mesh so there is no problem in messing I guess,

additionally I use GUMMEL and NEWTON numerical technique. Any suggestion how to remove the convergence issue?

I am studying diffusion of electron spins under different optical excitation conditions for some compound semiconductors quantum well.

Is there some methods to measure electrons temperature in a quantum well, other than PL?

I have seen many authors introduce the Dresselhaus contribution after averaging over the growth direction of a confining quantum well or wetting layer, thus giving the linear expression and a cubic (the latter often being neglected). However, in a dot, there is also quantum confinement in the x-y directions. Whilst this may not be so tightly confined as in the z direction, it is of the same order as a typical quantum well width or less, so shouldn't one also average the Dresselhaus Hamiltonian over these lateral dimensions?

If this were carried out, though, the Dresselhaus term would disappear altogether (since <kx> = <ky> = 0). This does seem to be implied by some authors, who only consider the Rashba term. So far, though, I have not seen any explicit comments to the effect that the Dresselhaus term disappears. I was wondering if there is an issue here and if so, is there a general consensus?

Martin Vaughan

In the literature there are many investigations and results on PL spectroscopy for thin films and quantum wells. But if I need the exact band gap of thick  film, for example InGaAsN alloys with nonuniform structure or constituent concentration in depth, is the Pl useful?

Can any one suggest me where can I get the e-book of 'Wave mechanics of electrons in metal' by Stainley Raimes ?

What methods can be used to model mathematically this problem.

Any detailed physical explanation would be highly appreciated.

Hello, 

I am currently working on the k.p method, and more specifically the application of this method, for the calculation of electronic bands in quantum well structure. 

I would like to use finite difference method for my calculation on matlab software, unfortunately I am a newbie in this technique. I think I can generate the code to create the discretized hamiltonian but I don't know how to resolve it and treat the eigenvalues. 

Does anyone have a detail algorithm, or some article related to the problem ? 

There are different numerical methods to solve the k.p Hamiltonian for multi quantum well structures such as the ultimate method which is based on a quadrature method (e.g. doi: 10.1016/0039-6028(94)90904-0), or one based on a finite-different method (e.g. doi: 10.1063/1.342118). In both, so-called spurious solutions can emerge and different methods exist to eliminate them (e.g. doi: 10.1063/1.3689821). However, I am searching for a comprehensive overview of the different numerical models and solutions regarding the spurious solutions to find advice on which numerical model and solution should be preferred.

Are they same? I read some of the post in RG regarding this question but didn't get a clear idea. 

Thank you for your time. 

electronic band gap from optical band gap

Dear Researchers and seniors

For example, if I am creating a bulk heterojunction of an organic material (pentacene) and PbS quantum dots, what are the key points that i should be looking out for? how can i know if it is even possile to mix those two?

Seen from the attached pictuire.

Based on bandgap requirement, Ic1=Ic2.

Because Ic2 and Ic3 are in series--> Ic2=Ic3

Because of size ratio n, Ic4=n*Ic3

So Ic4=n*Ic1

But Ic4 and Ic1 are in series, Ic4 should be equal to Ic1. It conflicts with Ic4=n*Ic1.

Where is my error in this above deduction? I'm puzzled about it.

I have read several papers and books from Professor Tapan, I have seen that he is almost devoted to spectral methods. I was wondering the type of technique for work. Will this based on spectral methods too or FD/FV methods. ?

Im looking to extract the quantification energy band of quantum wells from Silvaco Atlas, can help me to do it please?

Somebody show me how i can extract and plotting the transitions energies of quantum dots structure using silvaco please

I am trying to extract the real and imaginary dielectric constant for a 2D semiconductor with alternating layers of high and low dielectric (a quantum well material). I am using a Wollam Ellipsometer with their software and cannot produce a meaningful fit for the raw data. 

Are there any tricks towards finding the correct model? Also, I have a general idea of what the dielectric constant should be for each layer (6.1 and 2.1) and the models I've produced are not where close to that. 

How to use non parabolic band approximation for the analysis of interband effects of electrons for plasmonic device application?

How does surface electronic properties (i.e band structure, electron affinity and Ionization energy) vary from bulk to nano domain (i.e quantum well, nanorod etc.) and can we get any information of 2DEG formation using XPS or UPS.

I have a Si p-i-n diode structure with semiconducting iron disilicide quantum wells inside the i-Si layer. The width of the QWs is about 25 nm. Under reverse bias (at the avalanche mode), clear and significant red shift of the photoresponse edge is observed. I suppose that it results from quantum cinfined Stark effect. Next, I want to calculate energy shift of the ground state and compare it with experimental results. One can easily solve it for the case of the infinite quantum wells and weak field regime. In my case, the quantum well is finite and high field is applied.

Could anyone please help me with this situation?

As a starting point I have chosen Article (see attachement).

Applied Field range: 0,2-2,4 MV/m.

m*=0.83 m0(electrones) and 0.21 m0 for holes.

Barriers height is about 0.2 eV

Quantum well width is 25 nm

nano wire solar cell with kdse  structure.

Is there any difference between Surface Optical (SO) and Interface (IF) phonon modes in Raman spectra of Nanostructure and multi quantum wells (MQW), respectively ?

Im going to take as a example a quantum well (i.e 2DEG). Literature says that motion of electrons is quantised in the vertical direction for a 2DEG, therefore motion in the vertical direction is forbidden. The way I understand this is , if motion in the vertical direction is quantised, it means  the particle can take certain (discrete) energy values in that direction, meaning its k-vector in that direction can take certain values therefore it can move in that direction. I know I am wrong in my reasoning, I just do not know where? Some light please :)

I got extra peaks in UV-Vis of ZnS nanowires at 500 nm.

is there literatures or book to understand the complete details about How the 2D electron gas in the Quantum well structure (AlN/GaN) will influence its Raman modes and photoluminescence spectra?

How its band diagram look like?? how these structure will influence its phonon dispersion curves? How it will exactly affects the Raman modes of Quantum well structure?

Can someone provide me any references which report the relative magnitude of the slow decaying component to fast decaying component A2/A1 in a biexponential decay function of the time-resolved photoluminescence measurement for InGaAs/GaAs quantum wells? I would like to know the ratio A2/A1. The quantum wells could be based on homoepitaxy (on GaAs substrates) or heteroepitaxy (e.g. on Si substrates).

Im looking to know the main difference of using QDs and QWs in a solar cell, and when we can use QDs or QWs

How to handle tunneling modes and modes which pop-off from the well on applying external field-bending the potential profile. Looking for tunneling and unconfined modes by integrating the wavefunction square in well and surrounding regions while studying QCSE using effective mass model and restricting to lowest two solutions which would be the only significant solutions while operating away from band-edge were used but at the cost of generality. Latter works only for deep wells. Shallow wells will have eigen values popping-out and causing steps in calculated refractive indices or absorption coefficients while band-bending for ex. under external field. Using the continuum solutions is often recommended, I wish to avoid that since it makes the code computationally heavy.

I synthesized a nanostructure, ofcourse its dimensions were less than 100 nm. I doped a metal in the semiconductor nanostructure. Then Photoluminescence spectroscopy was carried out at 10 to 100 Kelvin with a step of 10 Kelvin and also at higher temerature. I found some of the peaks which were never reported before. So, I decided to calculate the electron transitions in the nanostructure which might be behaving like quantum well due to its dimensions. So, please let me know, is there any tool, software, mathematical model etc. which can be applied to calculate the band transition of the Doped semiconductor nanostructure, which might be behaving like quantum well?

Can the k.p method be used to short period superlattice like 1ML InAs/4 ML GaAs?

i mean to ask, they are what type of states and how they are helped out in quantum well......

we are working on a simple quantum well simulation (AlGaAs/GaAs) in Sentaurus Device

The k.p Luttinger Hamiltonian H for bulk semiconductors considering 8 bands (cb, hh, lh, so, each twice spin degenerate) can be found in many publications and text books, all using some different definitions of the wave function at the Gamma-point, but otherwise equivalent. Let us consider the explicit bulk Hamiltonian from this page (http://www.optronicsdesign.com/en/theory/hamiltonian.php), especially the general form Eq. (5).

Next, I like to compute the band structure of quantum wells, using the "ultimate concept" (see http://journals.aps.org/prb/abstract/10.1103/PhysRevB.48.8918). I would like to know how I construct the Hamiltonian for a quantum well from the bulk Hamiltonian. Here is how I understand the approach:

(1) All k.p parameters P get z-dependent P->P(z), for example the Luttinger parameters, the bulk band edges etc.

(2) I have to replace k_z P(z) and k_z^2 P(z) by 1/2[k_z + k_z'] P(k_z-k_z') and k_z k_z' P (k_z-k_z') according to Table I. P(k_z) is the Fourier transform of P(z). The resulting Hamiltonian now depends on k_z-k_z': H=H(k_z-k_z').

(3) I now have to solve the integral equation \int_{-\infty}^\infty dk_z' H(k_z-k_z') \Phi(k_z') = E \Phi(k_z) where \Phi is a spinor containing the different bulk band components of the lattice periodic part of the wave function.

(4) Numerically, I would have to write the integral as a sum, \sum_j dk_z^(j) H(k_z^(i)-k_z^(j)) \Phi(k_z^(j))  = E \Phi(k_z^(i)) and then formulate this as a matrix times a vector, see attached figure (note that a dk should be included in the matrix). In that, a double underline means that it is the bulk 8x8 matrix from step 2, and the single underlined \Phi is a 1x8 vector containing the 8 bulk components of the lattice periodic part of the wave function. So this is a (8*num_k_z)x(8*num_k_z) matrix, when num_k_z the number of k_z points in my numerical grid is.

(5) Solve the eigenvalue problem defined by step 4 for each k_\parallel I like and I should end up with the band structure of the system.

Is this in principle correct or did I miss something?

when we grow semipolar InGaN/GaN MQWs, if we add high temperature capping layer (AlGaN) to the MQWs, then the indium diffusion (desorption) happens. This fact is due to the high indium composition in the QWs (around 570nm). Do you have any ideas to suppress the indium diffusion? or normally (in c-plane or semipolar samples), how to change the growth condition to solve this kind of problem?

I want to measure I-V curve of an Infrared photodetector under illumination condition but I don't know which photon source to use. Would you please introduce me an appropriate infrared light source (brand and part number) to this aim? By the way, I need a source with wavelength of about 1550 nm.

 infrared photodetector

I mean in the context of light-matter interaction.

I would like to know if there is a simple method of calculating the absorption coefficient (alpha at different wavelengths) for a quantum well.

Cordially,

Semiconducting nanoparticles can be classified as QDs, Q wires and Q wells. I have doubt whether this quantum confinement is only in semiconductors. Is this aclassification based on confinement is possible in carbon materials or any conductors or any material other than semiconductors.