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General Questions and Answers / Re: Is there a fundamental physical limit for the On/Off ratio of a transistor?
« on: May 8, 2019, 16:28 »
Can anyone answer my question? many thanks!
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2
General Questions and Answers / Is there a fundamental physical limit for the On/Off ratio of a transistor?
« on: May 3, 2019, 17:57 »
Dear QuantumATK experts,
I would like to know if there exists a physical limit for the transistor On/Off ratio in terms of the channel material energy band gap.
For example, Si has a band gap of 1.14 eV and it may have some kind of limits on the maximum On/Off ratio in the form of exp(Eg/KT)?
I am not sure about this relation exists or not because I don't have a strong background in physics, but I would like to justify my result from the calculation.
Thanks!
I would like to know if there exists a physical limit for the transistor On/Off ratio in terms of the channel material energy band gap.
For example, Si has a band gap of 1.14 eV and it may have some kind of limits on the maximum On/Off ratio in the form of exp(Eg/KT)?
I am not sure about this relation exists or not because I don't have a strong background in physics, but I would like to justify my result from the calculation.
Thanks!
3
General Questions and Answers / How to interpret the iso-surface plot in transmission eigenstates analysis
« on: April 8, 2019, 21:44 »
Hi,
I would like to do an electron transport analysis using the transmission eigenstates tool in VNL.
I have the following two questions regarding the isosurface plot option for the eigenstates.
(1) For choosing the isovalue, should I choose the isovalue = the eigenvalue that I am interested in? e.g. I have a eigenvalue = 0.5, I should choose the isovalue = 0.5?
I checked this tutorial page and it seems to say so. https://docs.quantumatk.com/manual/Types/TransmissionEigenstate/TransmissionEigenstate.html#transmissioneigenstate-c
(2) The phase of the eigenstates is expressed using a color legend, what does the phase of the eigenstates mean? Does it have anything to do with the transmission contribution? How to interpret it physically?
Any help is appreciated! Thank you in advance.
I would like to do an electron transport analysis using the transmission eigenstates tool in VNL.
I have the following two questions regarding the isosurface plot option for the eigenstates.
(1) For choosing the isovalue, should I choose the isovalue = the eigenvalue that I am interested in? e.g. I have a eigenvalue = 0.5, I should choose the isovalue = 0.5?
I checked this tutorial page and it seems to say so. https://docs.quantumatk.com/manual/Types/TransmissionEigenstate/TransmissionEigenstate.html#transmissioneigenstate-c
(2) The phase of the eigenstates is expressed using a color legend, what does the phase of the eigenstates mean? Does it have anything to do with the transmission contribution? How to interpret it physically?
Any help is appreciated! Thank you in advance.
4
General Questions and Answers / Re: How to calculate to total inelastic transmission?
« on: April 8, 2019, 17:27 »
Can anyone respond to my question? Please help!
Thanks!
Thanks!
5
General Questions and Answers / How to calculate to total inelastic transmission?
« on: April 1, 2019, 20:29 »
Dear QuantumATK expert,
I would like to calculate the total inelastic transmission for a device at positive 0.2V bias. Should I sum up the inelasticTransmissionAsymmetricPositiveBias and inelasticTransmissionSymmetricPositiveBias because my device is at a positive biased state, and thus neglect for negative transmission? Or should I sum up all the 4 transmissions? (neg_sym, neg_asym, pos_sym, pos_asym)
What is the meaning for negative transmission generated at a positive biased state? i.e. the options in the plot settings of Inelastic Transmission Spectrum Analyzer of VNL.
Thank you!
I would like to calculate the total inelastic transmission for a device at positive 0.2V bias. Should I sum up the inelasticTransmissionAsymmetricPositiveBias and inelasticTransmissionSymmetricPositiveBias because my device is at a positive biased state, and thus neglect for negative transmission? Or should I sum up all the 4 transmissions? (neg_sym, neg_asym, pos_sym, pos_asym)
What is the meaning for negative transmission generated at a positive biased state? i.e. the options in the plot settings of Inelastic Transmission Spectrum Analyzer of VNL.
Thank you!
6
General Questions and Answers / Re: Is Dynamical matrix and Hamiltonian Derivative Independent of Spatial region
« on: March 11, 2019, 18:17 »
Thanks for the reply!
I don't understand that is it possible to choose to include or not include the gate effect?
My understanding is since the gate is there, its effect will be accounted for in the calculation. If we do not want to include the gate effect, then we have to delete the gate from the device, but that is not what we want.
In my test cases. I calculated an inelasticTransmissionSpectrum using the dHdR of different value of gate voltage VG, 0V and 1.5V. They gave me the exactly same result.
I just wonder if it doesn't matter what value of VG a dHdR is calculated at.
I don't understand that is it possible to choose to include or not include the gate effect?
My understanding is since the gate is there, its effect will be accounted for in the calculation. If we do not want to include the gate effect, then we have to delete the gate from the device, but that is not what we want.
In my test cases. I calculated an inelasticTransmissionSpectrum using the dHdR of different value of gate voltage VG, 0V and 1.5V. They gave me the exactly same result.
I just wonder if it doesn't matter what value of VG a dHdR is calculated at.
7
General Questions and Answers / Is there a way to calculate the local inelastic current?
« on: March 6, 2019, 22:12 »
Dear ATK experts,
I am studying the e-ph interaction in a two-probe device. I am wondering if it is possible to calculate the local inelastic current and plot them pictorially, just like the TransmissionPathway did.
From my understanding, the transmission pathways split the transmission coefficient into local bond contributions Tij and plot them using the volume-weighted arrow on the atomic bonds, which is pretty nice and helps a lot in carrier transport analyzing. But it seems like it only calculates from the regular transmission coefficient. i.e. the transmission without considering e-ph interaction.
So my question is, in ATK, is there a way to calculate the local inelastic current which takes into account the e-ph interaction effect?
Thanks!
I am studying the e-ph interaction in a two-probe device. I am wondering if it is possible to calculate the local inelastic current and plot them pictorially, just like the TransmissionPathway did.
From my understanding, the transmission pathways split the transmission coefficient into local bond contributions Tij and plot them using the volume-weighted arrow on the atomic bonds, which is pretty nice and helps a lot in carrier transport analyzing. But it seems like it only calculates from the regular transmission coefficient. i.e. the transmission without considering e-ph interaction.
So my question is, in ATK, is there a way to calculate the local inelastic current which takes into account the e-ph interaction effect?
Thanks!
8
General Questions and Answers / Re: Is Dynamical matrix and Hamiltonian Derivative Independent of Spatial region
« on: March 6, 2019, 21:59 »
Thank you for the reply!
I have read about this tutorial case study. The use of bulk dynamical matrix and bulk Hamiltonian derivatives does help for reducing the calculation time. But it only valid for a homogenous device configuration as I understand.
The device that I am studying have defects in the scattering region, i.e. it is not homogenous along the c direction. Therefore I will need to calculate the dynamical matrix and Hamiltonian derivatives for the whole device instead of its bulk configuration, in order for calculating the inelasticTransmissionSpectrum.
Therefore my question is, if I want to calculate the inelasticTransmissionSpectrum at different gate voltages (suppose I have a transistor device), do I need to calculate the dynamical matrix and Hamiltonian derivatives at these gate voltages as prior for the corresponding inelasticTransmissionSpectrum calculation? Or calculating them at one gate voltage is enough and can be used for all other gate voltages?
i.e. Are dynamical matrix and Hamiltonian derivatives independent of gate voltage?
Based on my understanding of them from the ATK manual, I feel like they are. And I did some toy case study which confirmed my guess.
Can you provide some opinion about this?
Thanks!
I have read about this tutorial case study. The use of bulk dynamical matrix and bulk Hamiltonian derivatives does help for reducing the calculation time. But it only valid for a homogenous device configuration as I understand.
The device that I am studying have defects in the scattering region, i.e. it is not homogenous along the c direction. Therefore I will need to calculate the dynamical matrix and Hamiltonian derivatives for the whole device instead of its bulk configuration, in order for calculating the inelasticTransmissionSpectrum.
Therefore my question is, if I want to calculate the inelasticTransmissionSpectrum at different gate voltages (suppose I have a transistor device), do I need to calculate the dynamical matrix and Hamiltonian derivatives at these gate voltages as prior for the corresponding inelasticTransmissionSpectrum calculation? Or calculating them at one gate voltage is enough and can be used for all other gate voltages?
i.e. Are dynamical matrix and Hamiltonian derivatives independent of gate voltage?
Based on my understanding of them from the ATK manual, I feel like they are. And I did some toy case study which confirmed my guess.
Can you provide some opinion about this?
Thanks!
9
General Questions and Answers / Is Dynamical matrix and Hamiltonian Derivative Independent of Spatial region
« on: March 3, 2019, 17:15 »
Hi,
I am calculating the InelasticTransmissionSpectrum for a defective GNR device which requires DynamicalMatrix and HamiltonianDerivative calculated first.
I am wondering if the Dynamical matrix and Hamiltonian Derivative calculation are independent of the spatial region? i.e. For the same device configuration with different Gate voltage on the metallic region, do I need to calculate the Dynamical matrix and Hamiltonian Derivative differently? Or I can use the Dynamical matrix and Hamiltonian Derivative calculated at one gate voltage for all other gate voltage.
I am studying the transfer characteristics of the device, so I need to calculate the inelastic current of the device at different gate voltage.
Thank you!
I am calculating the InelasticTransmissionSpectrum for a defective GNR device which requires DynamicalMatrix and HamiltonianDerivative calculated first.
I am wondering if the Dynamical matrix and Hamiltonian Derivative calculation are independent of the spatial region? i.e. For the same device configuration with different Gate voltage on the metallic region, do I need to calculate the Dynamical matrix and Hamiltonian Derivative differently? Or I can use the Dynamical matrix and Hamiltonian Derivative calculated at one gate voltage for all other gate voltage.
I am studying the transfer characteristics of the device, so I need to calculate the inelastic current of the device at different gate voltage.
Thank you!
10
General Questions and Answers / Is it possible to calculate Inelastic current for defective device configuration
« on: February 21, 2019, 18:34 »
Hi,
Is it possible to use the InelasticTransmissionSpectrum module in ATK to account for e-ph interaction and calculate the inelastic current for a defective device? e.g. a GNR tunneling transistor where the GNR has edge/vacancy defects.
There is already a QuantumWise tutorial of calculating TransmissionSpectrum for a GNR device with Stone-Wales defect. I wonder if the InelasticTransmissionSpectrum also applies to defective structures.
If yes, are the procedures different from calculating the inelastic current of a pristine device?
Thanks!
Is it possible to use the InelasticTransmissionSpectrum module in ATK to account for e-ph interaction and calculate the inelastic current for a defective device? e.g. a GNR tunneling transistor where the GNR has edge/vacancy defects.
There is already a QuantumWise tutorial of calculating TransmissionSpectrum for a GNR device with Stone-Wales defect. I wonder if the InelasticTransmissionSpectrum also applies to defective structures.
If yes, are the procedures different from calculating the inelastic current of a pristine device?
Thanks!
11
General Questions and Answers / Re: How to export the spectral current from InelasticTransmission spectrum
« on: January 23, 2019, 21:42 »
Anyone has any thought about my question?
12
General Questions and Answers / Re: How to export the spectral current from InelasticTransmission spectrum
« on: January 21, 2019, 19:51 »
Thank for the reply!
What I am interested in is the Spectral current plot type provided in the Inelastic Transmission Spectrum Analyzer. (see attached image)
I can see the spectral current but cannot export the data for further processing.
What I am interested in is the Spectral current plot type provided in the Inelastic Transmission Spectrum Analyzer. (see attached image)
I can see the spectral current but cannot export the data for further processing.
13
General Questions and Answers / How to export the spectral current from InelasticTransmission spectrum
« on: January 20, 2019, 20:05 »
Hi,
Is there a way to calculate the spectral current from the InelasticTransmission spectrum object? e.g. just like the regular method used in normal transmission spectrum TransmissionSpectrum.spectralCurrent()?
I checked the manual, but there is no such method or any related method for InelasticTransmission class.
In the VNL, from the Inelastic Transmission Spectrum Analyzer I can see the spectral current, but I don't know how to export the data.
Thank you in advance for any help!
Is there a way to calculate the spectral current from the InelasticTransmission spectrum object? e.g. just like the regular method used in normal transmission spectrum TransmissionSpectrum.spectralCurrent()?
I checked the manual, but there is no such method or any related method for InelasticTransmission class.
In the VNL, from the Inelastic Transmission Spectrum Analyzer I can see the spectral current, but I don't know how to export the data.
Thank you in advance for any help!
14
General Questions and Answers / Re: Inconsistency in the current analysis for InelasticTransmissionSpectrum
« on: January 11, 2019, 16:24 »
Thank you for the reply!
I think I have got the answer.
"In situations where there are no electrode states at the Fermi energy, like in a low- or un-doped semiconductor, the direct use of the LOE and XLOE expressions will result in zero inelastic currents, when evaluated at the Fermi energy. In that case, the inelastic transmission spectra must be calculated at a range of energies (like the normal TransmissionSpectrum). The current can then be calculated as:
bias = numpy.linspace(-0.1,0.1,100)*Volt
current = inelastic_transmission_spectrum.inelasticCurrentIntegral(bias=bias)"
I think I have got the answer.
"In situations where there are no electrode states at the Fermi energy, like in a low- or un-doped semiconductor, the direct use of the LOE and XLOE expressions will result in zero inelastic currents, when evaluated at the Fermi energy. In that case, the inelastic transmission spectra must be calculated at a range of energies (like the normal TransmissionSpectrum). The current can then be calculated as:
bias = numpy.linspace(-0.1,0.1,100)*Volt
current = inelastic_transmission_spectrum.inelasticCurrentIntegral(bias=bias)"
15
General Questions and Answers / Re: Inconsistency in the current analysis for InelasticTransmissionSpectrum
« on: January 10, 2019, 17:02 »
Thank you for the reply!
But can you give me a little more details?
Why only the bias window (-0.1eV,0.1eV) is considered in calculating the total current?
Thanks!
But can you give me a little more details?
Why only the bias window (-0.1eV,0.1eV) is considered in calculating the total current?
Thanks!