Thermal Modeling of Very Small Scale Devices

2004 ◽  
Author(s):  
A. Bulusu ◽  
D. G. Walker
Keyword(s):  
Phonon Scattering ◽  
Electronic Device ◽  
Electron Tunneling ◽  
Quantum Effects ◽  
Small Scale ◽  
Channel Current ◽  
Scattering Rate ◽  
Scattering Effects ◽  
Computationally Intensive ◽  
Electron Phonon Scattering

As electronic device dimensions shrink down to the nanoscale regime, quantum effects such as electron tunneling and quantum confinement become significant. Along with quantum effects, various scattering processes such as carrier-carrier and carrier-defect scattering will influence device performance. Many transport models are not mature enough to couple the thermal effects with electronic solutions at such small scales. Incorporation of strong scattering influences on the electron transport in most cases is extremely difficult and computationally intensive. In this paper, we study a simple model that allows for integration of electron-phonon scattering effects in a nanotransistor. An acoustic deformation potential based electron-phonon scattering model is used to incorporate scattering in the device. A 7.5% drop in channel current was observed for a scattering rate of 1013/sec while current flow dropped by 50% for higher scattering rates. The effective channel resistance due to scattering was found to increase by a factor of 1.3. The results are compared to the I-V characteristics obtained using the non-equilibrium Green’s function (NEGF) formalism and were found to match well. The effect of phase-breaking scattering was also studied using NEGF where a 25% decrease in channel current was obtained thus demonstrating the importance of including scattering effects with quantum transport.

Modeling of Electron Transport in Thin Films With Quantum and Scattering Effects

2005 ◽  
Author(s):  
A. Bulusu ◽  
D. G. Walker
Keyword(s):  
Electron Transport ◽  
Phonon Scattering ◽  
Simulation Models ◽  
Quantum Effects ◽  
Effect Of Temperature ◽  
Channel Current ◽  
Couple Quantum ◽  
Scattering Effects ◽  
Computationally Intensive ◽  
Electron Phonon Scattering

With device dimensions shrinking to nanoscales, quantum effects such as confinement and tunneling become significant in electron transport. In addition, thermal transport in devices is directly coupled to charge transport even in highly scaled devices. While electron-phonon scattering usually helps restore thermodynamic equilibrium, shrinking device dimensions may not ensure enough scattering to restore equilibrium. The simultaneous consideration of scattering effects, which is usually described as particle behavior, and quantum effects, which are wave in nature, is extremely difficult and computationally intensive. Most device transport simulation models are not mature enough to couple quantum effects with strong scattering effects. In this paper, we couple quantum effects and scattering influences on electron transport using the non-equilibrium Green’s function formalism. Results indicate a 45 to 70 percent decrease in channel current for the case of near-elastic, phase-breaking, electron-phonon scattering. The single phonon energies ranged from 2meV to 20meV. The results illustrate the importance of including scattering effects with quantum transport. In addition, the NEGF model is used to assess the effect of temperature on device characteristics of thin film superlattices whose applications include thermoelectric cooling of electronic and optoelectronic systems. Results show the predicted Seebeck coefficient to be in good agreement with the measured values.

scholarly journals Modeling of Thermoelectric Properties of Semi-Conductor Thin Films With Quantum and Scattering Effects

2006 ◽  
Vol 129 (4) ◽  
pp. 492-499 ◽  
Author(s):  
A. Bulusu ◽  
D. G. Walker
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Quantum Effects ◽  
Effect Of Temperature ◽  
Fundamental Parameters ◽  
Scattering Effects ◽  
Electron Phonon Scattering

Several new reduced-scale structures have been proposed to improve thermoelectric properties of materials. In particular, superlattice thin films and wires should decrease the thermal conductivity, due to increased phonon boundary scattering, while increasing the local electron density of states for improved thermopower. The net effect should be increased ZT, the performance metric for thermoelectric structures. Modeling these structures is challenging because quantum effects often have to be combined with noncontinuum effects and because electronic and thermal systems are tightly coupled. The nonequilibrium Green’s function (NEGF) approach, which provides a platform to address both of these difficulties, is used to predict the thermoelectric properties of thin-film structures based on a limited number of fundamental parameters. The model includes quantum effects and electron-phonon scattering. Results indicate a 26–90 % decrease in channel current for the case of near-elastic, phase-breaking, electron-phonon scattering for single phonon energies ranging from 0.2 meV to 60 meV. In addition, the NEGF model is used to assess the effect of temperature on device characteristics of thin-film heterojunctions whose applications include thermoelectric cooling of electronic and optoelectronic systems. Results show the predicted Seebeck coefficient to be similar to measured trends. Although superlattices have been known to show reduced thermal conductivity, results show that the inclusion of scattering effects reduces the electrical conductivity leading to a significant reduction in the power factor (S2σ).

The effect of electron effective mass mismatch on electron - phonon scattering rate in a quantum well

1997 ◽  
Vol 12 (3) ◽  
pp. 296-299 ◽  
Author(s):  
Zheng Yisong ◽  
Lu Tianquan ◽  
Wang Yiding ◽  
Wu Xuhong ◽  
Zhang Chengxiang ◽  
...  
Keyword(s):  
Quantum Well ◽  
Effective Mass ◽  
Phonon Scattering ◽  
Electron Effective Mass ◽  
Scattering Rate ◽  
Electron Phonon Scattering

Anisotropy of the electron-phonon scattering rate in metals

1975 ◽  
Vol 19 (1-4) ◽  
pp. 49-50 ◽  
Author(s):  
V. F. Gantmakher ◽  
V. A. Gasparov
Keyword(s):  
Phonon Scattering ◽  
Scattering Rate ◽  
Electron Phonon Scattering

Point measurements of the electron-phonon scattering rate in silver

1983 ◽  
Vol 50 (3-4) ◽  
pp. 379-389 ◽  
Author(s):  
V. A. Gasparov ◽  
J. Lebech ◽  
K. Saermark
Keyword(s):  
Phonon Scattering ◽  
Scattering Rate ◽  
Electron Phonon Scattering

The Dynamics of a Small-Scale Portable Electronics Device Under Impact Stimuli

2006 ◽  
Author(s):  
Gerard A. Kelly ◽  
Jeff M. Punch ◽  
Suresh Goyal
Keyword(s):  
Electronic Device ◽  
Initial Conditions ◽  
Electronic Devices ◽  
Drop Test ◽  
Small Scale ◽  
Portable Electronics ◽  
Simulation Techniques ◽  
Acceleration Data ◽  
Computationally Intensive ◽  
Free Drop

The reliability of portable electronic devices is of critical importance due to the consumer boom in mobile telephony in recent years. Impact is a key driver of failure in portable electronics and, in current design practice, extensive testing is used in conjunction with finite element simulations to ensure product reliability under impact stimuli. Testing is time-consuming and expensive – both free-drop and constrained drop tests are usually applied – and simulation techniques are very computationally intensive. The response of portable electronic devices to impact is currently not well understood, and there is clear need for investigation into the range of acceleration levels experienced by a representative model of a portable electronic device on impact. In this paper, free-drop testing was carried out on test vehicles representative of a typical mobile phone in order to acquire acceleration data from impact events. Drop test vehicles from Nylon and aluminium were used to provide a means of comparison for diverse material properties. The primary conclusion was that the dynamics of each drop event were highly sensitive to the initial conditions of the drop test, which was evident from wide variances in the acceleration data.

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