Support

Support Options

Submit a Support Ticket

 
Version 47
by Michael Anderson
Version 48
by Michael Anderson

Deletions or items before changed

Additions or items after changed

1 [[Image(picture_11.png, 700px, class=align-center)]]
2
3 -
This nanoHUB "topic page" provides an easy access to selected nanoHUB educational material on semiconductor devices that is openly accessible.
+
This nanoHUB "topic page" provides an easy access to selected nanoHUB educational material on computational electronics that is openly accessible.
4
5 We invite users to participate in this open source, interactive educational initiative:
6
7 * [http://www.nanohub.org/contribute/Contribute content] by uploading it to the nanoHUB. (See "Contribute Content") on the nanoHUB mainpage.
8 * Provide feedback for the items you use on the nanoHUB through the review system. (Please be explicit and provide constructive feedback.)
9 * Let us know when things do not work by filing a ticket through the nanoHUB "Help" feature on every page.
10 * Finally, let us know what you are doing and [http://www.nanohub.org/feedback/suggestions/your suggestions] improving the nanoHUB by using the "Feedback" section, which you can find under "[http://www.nanohub.org/support/Support]"
11
12 Thank you for using the nanoHUB, and be sure to [http://www.nanohub.org/feedback/success_story/share your nanoHUB success stories] with us. We like to hear from you, and our sponsors need to know that the nanoHUB is having impact.
13
14 [[Div(start, class=clear)]][[Div(end)]]
15
16 -
The purpose of the ACUTE tool-based curriculum is to introduce interested scientists from academia and industry in advanced simulation methods needed for proper modeling of state-of-the-art nanoscale devices. The multiple scale transport in doped semiconductors is summarized in the figure below, in terms of the transport regimes, relative importance of the scattering mechanisms, and possible applications.
+
The purpose of the ACUTE tool-based curriculum is to introduce interested scientists from academia and industry to the advanced methods of simulation needed for the proper modeling of state-of-the-art nanoscale devices. The multiple scale transport in doped semiconductors is summarized in the figure below, in terms of the transport regimes, relative importance of the scattering mechanisms, and possible applications.
17
18 [[Image(intro1.png, 250px, class=align-left)]]
19 [[Div(start, class=clear)]][[Div(end)]]
20
21 Figure: Relationship between various transport regimes and significant length-scales.
22
23 [[Image(intro2.png, 250px, class=align-left)]]
24 [[Div(start, class=clear)]][[Div(end)]]
25
26 -
We first discuss the energy band structure that enters as an input to any device simulator. We then begin with the discussion of simulators that involve the drift-diffusion model, and then move into simulations that involve hydrodynamic and energy balance transport and conclude the semi-classical transport modeling with application of particle-based device simulation methods.
+
We first discuss the energy band structure that enters as an input to any device simulator. We then move on to a discussion of simulators that involve the drift-diffusion model, and then to simulations that involve hydrodynamic and energy-balance transport, and conclude the semi-classical transport modeling with application of particle-based device simulation methods.
27
28 -
Having discussed and utilized the semiclassical simulation tools and their applications, we then move into inclusion of quantum corrections into classical simulators. The final set of tools is dedicated to the far-from equilibrium transport, where we will utilize the concept of pure and mixed states and the distribution function. Several tools that utilize different methods will be used for that purpose. We will utilize tools that use the recursive Green’s function method and its variant, the Usuki method. Also, we will utilize the Contact Block Reduction tool as the most efficient and most complete way of solving the quantum transport problem since this method allows one to simultaneously calculate source-drain current and gate leakage which is not the case, for example, with the Usuki and the recursive Green’s function techniques that are in fact quasi-1D in nature for transport through a device. A table that shows the advantages and the limitation of various semi-classical and quantum transport simulation tools is presented below.
+
Having discussed and utilized the semiclassical simulation tools and their applications, we then move on to include quantum corrections into the classical simulators. The final set of tools is dedicated to the far-from equilibrium transport, where we will utilize the concept of pure and mixed states and the distribution function. Several tools that utilize different methods will be used for that purpose. We will utilize tools that use the recursive Green’s function method and its variant, the Usuki method. Also, we will utilize the Contact Block Reduction tool as the most efficient and most complete way of solving the quantum transport problem since this method allows one to simultaneously calculate source-drain current and gate leakage which is not the case, for example, with the Usuki and the recursive Green’s function techniques that are in fact quasi-1D in nature for transport through a device. A table that shows the advantages and the limitation of various semi-classical and quantum transport simulation tools is presented below.
29
30 [[Image(intro3.png, 250px, class=align-left)]]
31 [[Div(start, class=clear)]][[Div(end)]]
32
33 More details on the actual tool design and information on commercial tool usage can be found on the web pages:
34
35 [[Resource(4921)]]
36
37 [[Resource(5092)]]
38
39
40
41 == Energy Bands and Effective Masses ==
42
43 === [/tools/acute/ Piece-Wise Constant Potential Barrier Tool in ACUTE]– Open Systems ===
44
45 The [/tools/acute/ Piece-Wise Constant Potential Barrier Tool in ACUTE] allows calculation of the transmission and the reflection coefficient of arbitrary five, seven, nine, eleven and 2n-segment piece-wise constant potential energy profile. For the case of multi-well structure it also calculates the quasi-bound states so it can be used as a simple demonstration tool for the formation of energy bands.
46
47 [[Image(pcpbt.png, 200px, class=align-left)]]
48 [[Div(start, class=clear)]][[Div(end)]]
49
50 Also, it can be used in the case of stationary perturbation theory exercises to test the validity of, for example, the first order and the second order correction to the ground state energy of the system due to small perturbations of, for example, the confining potential. The PCPBT tool can also be used to test the validity of the WKB approximation for triangular potential barriers.
51
52 [[Div(start, class=clear)]][[Div(end)]]
53
54 Exercises:
55
56 [[Div(start, class=clear)]][[Div(end)]]
57
58 * [[Resource(4831)]]
59
60 * [[Resource(4833)]]
61
62 * [[Resource(4853)]]
63
64 * [[Resource(4873)]]
65
66 * [[Resource(5319)]]
67
68 * [[Resource(4849)]]
69
70 * [[Resource(5102)]]
71
72 * [[Resource(5130)]]
73
74 [[Div(start, class=clear)]][[Div(end)]]
75
76
77 === [/tools/acute/ Periodic Potential Lab in ACUTE] ===
78
79 The [/tools/acute/ Periodic Potential Lab in ACUTE] solves the time independent Schroedinger Equation in a 1-D spatial potential variation. Rectangular, triangular, parabolic (harmonic), and Coulomb potential confinements can be considered. The user can determine energetic and spatial details of the potential profiles, compute the allowed and forbidden bands, plot the bands in a compact and an expanded zone,
80
81 [[Image(ppl.png, 250px, class=align-left)]]
82 [[Div(start, class=clear)]][[Div(end)]]
83
84 and compare the results against a simple effective mass parabolic band. Transmission is also calculated. This Lab also allows the students to become familiar with the reduced zone and expanded zone representation of the dispersion relation (E-k relation for carriers).
85
86 Exercises:
87
88 * [[Resource(4851)]]
89
90 [[Div(start, class=clear)]][[Div(end)]]
91
92
93 === [/tools/acute/ Bandstructure Lab in ACUTE] ===
94
95 In solid-state physics, the electronic band structure (or simply band structure) of a solid describes ranges of energy that an electron is "forbidden" or "allowed" to have. It is due to the diffraction of the quantum mechanical electron waves in the periodic crystal lattice. The band structure of a material determines several characteristics, in particular its electronic and optical properties. The [/tools/acute/ Bandstructure Lab in ACUTE] tool enables the study of bulk dispersion relationships of Si, !GaAs, !InAs. Plotting the full dispersion relation of different materials, students first get familiar with a band-structure of direct band-gap (!GaAs, !InAs) and indirect band-gap semiconductors (Si). For the case of multiple conduction band valleys one has to determine first the Miller indices of one of the equivalent valleys and from that information it immediately follows how many equivalent conduction bands one has in Si and Ge, for example.
96
97 [[Image(bsl.png, 250px, class=align-left)]]
98 [[Div(start, class=clear)]][[Div(end)]]
99
100 In advanced applications, the users can apply tensile and compressive strain and observe the variation in the bandstructure, bandgaps, and effective masses. Advanced users can also study bandstructure effects in ultra-scaled (thin body) quantum wells, and nanowires of different cross sections. Bandstructure Lab uses the sp3s*d5 tight binding method to compute E(k) for bulk, planar, and nanowire semiconductors.
101
102 Exercises:
103
104 * [[Resource(5201)]]
105
106 * [[Resource(5031)]]
107
108 * [[Resource(4890)]]
109
110 * [[Resource(4880)]]
111
112
113 [[Div(start, class=clear)]][[Div(end)]]
114
115
116 ==Drift-Diffusion and Energy Balance Simulations==
117
118
119 === [/tools/acute/ PADRE Tool in ACUTE] – Modeling of Si-based devices===
120
121 [/tools/acute/ PADRE Tool in ACUTE] is a 2D/3D simulator for electronic devices, such as MOSFET transistors.
122
123 [[Image(padre.png, 250px, class=align-left)]]
124 [[Div(start, class=clear)]][[Div(end)]]
125
126 It can simulate physical structures of arbitrary geometry--including heterostructures--with arbitrary doping profiles, which can be obtained using analytical functions or directly from multidimensional process simulators such as Prophet.
127 For each electrical bias, [/tools/acute/ PADRE Tool in ACUTE] solves a coupled set of partial differential equations (PDEs). A variety of PDE systems are supported which form a hierarchy of accuracy: (1) electrostatic (Poisson equation), (2) drift-diffusion (including carrier continuity equations), (3) energy balance (including carrier temperature) and (4) electrothermal (including lattice heating).
128
129 Several example problems that utilize [/tools/acute/ PADRE Tool in ACUTE] are given below:
130
131 * [[Resource(229)]]
132
133 * [[Resource(4894)]]
134
135 * [[Resource(4896)]]
136
137 * [[Resource(452)]]
138
139 * [[Resource(4906)]]
140
141 * [[Resource(3984)]]
142
143 * [[Resource(5051)]]
144
145 A variety of supplemental documents are available that deal with the PADRE software and TCAD simulation:
146
147 * [/site/resources/tools/padre/doc/index.html User Manual]
148
149 * [/site/resources/2006/06/01581/intro_dd_padre_word.pdf Abbreviated First Time User Guide]
150
151
152 A set of course notes on Computational Electronics with detailed explanations on bandstructure, pseudopotentials, numerical issues, and drift diffusion is also available.
153
154 * [[Resource(1516)]]
155
156 * [[Resource(980)]]
157
158
159 ===SILVACO Simulator – Modeling of Si-based and III-V devices===
160
161 In preparation.
162
163
164
165 == Particle-Based Simulators ==
166
167 === [/tools/acute/ Bulk Monte Carlo Lab in ACUTE] ===
168
169 [[Image(mc.png, 250px, class=align-left)]]
170 [[Div(start, class=clear)]][[Div(end)]]
171
172 The [/tools/acute/ Bulk Monte Carlo Lab in ACUTE] calculates the bulk values of the electron drift velocity, electron average energy and electron mobility for electric fields applied in arbitrary crystallographic direction in both column 4 (Si and Ge) and III-V (GaAs, SiC and GaN) materials. All relevant scattering mechanisms for the materials being considered have been included in the model.
173
174 [[Image(scattering.png, 250px class=align-left)]]
175 [[Div(start, class=clear)]][[Div(end)]]
176
177 Detailed derivation of the scattering rates for most of the scattering mechanisms included in the model can be found on Prof. Vasileska personal web-site http://www.eas.asu.edu/~vasilesk (look under class EEE534 Semiconductor Transport). Description of the Monte Carlo method used to solve the Boltzmann Transport Equation and implementation details of the tool are given in the
178
179 [[Resource(4843)]]
180
181 Available also is a voiced presentation
182
183 [[Resource(4439)]]
184
185 that gives more insight on the implementation details of the Ensemble Monte Carlo technique for the solution of the Boltzmann Transport Equation. Examples of simulations that can be performed with this tool are given below:
186
187 [[Resource(4845)]]
188
189 Exercises:
190
191 * [[Resource(5047)]]
192
193 * [[Resource(5277)]]
194
195 * [[Resource(5275)]]
196
197 * [[Resource(5321)]]
198
199 * [[Resource(5323)]]
200
201
202 === [/tools/acute/ Quamc2D Lab in ACUTE] ===
203
204 [/tools/acute/ Quamc2D Lab in ACUTE] (pronunciation: quamsee) 2-D is effectively a quasi three-dimensional quantum-corrected semiclassical Monte Carlo transport simulator for conventional and non-conventional MOSFET devices.
205
206 [[Image(quamc2d1.png, 250px, class=align-left)]]
207 [[Div(start, class=clear)]][[Div(end)]]
208
209 Device structures that can be simulated.
210
211 [[Image(quamc2d2.png, 250px, class=align-left)]]
212 [[Div(start, class=clear)]][[Div(end)]]
213
214 Phenomena that can be explained
215
216 A parameter-free quantum field approach has been developed and utilized quite successfully in order to capture the size-quantization effects in nanoscale MOSFETs. The method is based on a perturbation theory around thermodynamic equilibrium and leads to a quantum field formalism in which the size of an electron depends upon its energy. This simulator uses different self-consistent event-biasing schemes for statistical enhancement in the Monte-Carlo device simulations. Enhancement algorithms are especially useful when the device behavior is governed by rare events in the carrier transport process. A bias technique, particularly useful for small devices, is obtained by injection of hot carriers from the boundaries. Regarding the Monte Carlo transport kernel, the explicit inclusion of the longitudinal and transverse masses in the silicon conduction band is done in the program using the Herring-Vogt transformation. Intravalley scattering is limited to acoustic phonons. For the intervalley scattering, both g- and f-phonon processes have been included.
217
218 * [[Resource(4520)]]
219
220 * [[Resource(4543)]]
221
222 * [[Resource(4443)]]
223
224 * [[Resource(4439)]]
225
226 * [[Resource(5127)]]
227
228 Exercises:
229
230
231 ===Thermal Particle-Based Device Simulator===
232
233 In preparation.
234
235 Exercises and Other Resources:
236
237 * [[Resource(5350)]]
238
239
240 ==Inclusion of Quantum Corrections into Semi-Classical Simulation Tools==
241
242
243 === [/tools/acute/ SCHRED in ACUTE] ===
244
245 [/tools/acute/ SCHRED in ACUTE] calculates the envelope wavefunctions and the corresponding bound-state energies in a typical MOS (Metal-Oxide-Semiconductor) or SOS (Semiconductor-Oxide- Semiconductor) structure and a typical SOI structure by solving self-consistently the one-dimensional (1D) Poisson equation and the 1D Schrodinger equation.
246
247 [[Image(schred.png, 250px, class=align-left)]]
248 [[Div(start, class=clear)]][[Div(end)]]
249
250 To better understand the operation of [/tools/acute/ SCHRED in ACUTE] tool and the physics of MOS capacitors please refer to:
251
252 * [[Resource(4794)]]
253
254 * [[Resource(4796)]]
255
256 * [[Resource(5087)]]
257
258 * [[Resource(5127)]]
259
260 Exercises:
261
262 * [[Resource(4900)]]
263
264 * [[Resource(4902)]]
265
266 * [[Resource(4904)]]
267
268
269 === [/tools/acute/ 1D Heterostructure Tool in ACUTE] ===
270
271 The [/tools/acute/ 1D Heterostructure Tool in ACUTE] simulates confined states in 1D heterostructures by calculating charge self-consistently in the confined states, based on a quantum mechanical description of the one dimensional device. The greater interest in HEMT devices is motivated by the limits that will be reached with scaling of conventional transistors. The [/tools/acute/ 1D Heterostructure Tool in ACUTE] in that respect is a very valuable tool for the design of HEMT devices as one can determine, for example, the position and the magnitude of the delta-doped layer, the thickness of the barrier and the spacer layer for which one maximizes the amount of free carriers in the channel which, in turn, leads to larger drive current. This is clearly illustrated in the examples below.
272
273 [[Image(1dhet1.png, 180px, class=align-left)]]
274 [[Image(1dhet2.png, 180px, class=align-left)]]
275 [[Div(start, class=clear)]][[Div(end)]]
276
277 Exercises:
278
279 * [[Resource(5231)]]
280
281 * [[Resource(5233)]]
282
283
284 The most commonly used semiconductor devices for applications in the GHz range now are !GaAs based MESFETs, HEMTs and HBTs. Although MESFETs are the cheapest devices because they can be realized with bulk material, i.e. without epitaxially grown layers, HEMTs and HBTs are promising devices for the near future. The advantage of HEMTs and HBTs is a factor of 2 to 3 higher power density compared to MESFETs which leads to significantly smaller chip size.
285
286 HEMTs are field effect transistors where the current flow between two ohmic contacts, Source and Drain, and it is controlled by a third contact, the Gate. Most often the Gate is a Schottky contact. In contrast to ion implanted MESFETs, HEMTs are based on epitaxially grown layers with different band gaps Eg.
287
288
289
290 ==Quantum Transport==
291
292
293 === Recursive Green's Function Method for Modeling RTD's===
294
295 in preparation.
296
297
298 === [/tools/acute/ nanoMOS in ACUTE] ===
299
300 [/tools/acute/ nanoMOS in ACUTE] is a 2-D simulator for thin body (less than 5 nm), fully depleted, double-gated n-MOSFETs. A choice of five transport models is available (drift-diffusion, classical ballistic, energy transport, quantum ballistic, and quantum diffusive). The transport models treat quantum effects in the confinement direction exactly and the names indicate the technique used to account for carrier transport along the channel. Each of these transport models is solved self-consistently with Poisson's equation. Several internal quantities such as subband profiles, subband areal electron densities, potential profiles and I-V information can be obtained from the source code.
301
302 [[Image(nanomos.png, 250px, class=align-left)]]
303 [[Div(start, class=clear)]][[Div(end)]]
304
305 [[Resource(1305)]] 3.0 includes an improved treatment of carrier scattering. Some important information about [/tools/acute/ nanoMOS in ACUTE] can be found on the following links:
306
307 * [[Resource(2845)]]
308
309 * [[Resource(1533)]]
310
311
312 ===CBR===
313
314 in preparation.
315
316
317
318 ==Atomistic Modeling==
319
320
321 === [/tools/acute/ NEMO3D in ACUTE] ===
322
323 [/tools/acute/ NEMO3D in ACUTE] calculates eigenstates in (almost) arbitrarily shaped semiconductor structures in the typical column IV and III-V materials. Atoms are represented by the empirical tight binding model using s, sp3s*, or sp3d5s* models with or without spin. Strain is computed using the classical valence force field (VFF) with various Keating-like potentials.
324
325 [[Image(modeling_agenda5.gif, 250px, class=align-left)]]
326 [[Div(start, class=clear)]][[Div(end)]]
327
328 [/tools/acute/ NEMO3D in ACUTE] has been used to analyze quantum dots, alloyed quantum dots, long range strain effects on quantum dots, effects of wetting layers, piezo-electric effects in quantum dots, quantum dot nuclear spin interactions, quantum dot phonon spectra, coupled quantum dot systems, miscut Si quantum wells with SiGe alloy buffers, core-shell nanowires, allyed nanowires, phosphorous impurities in Silicon (P:Si qbits), bulk alloys.
329
330 [[Image(qdot.png, 250px, class=align-left)]]
331 [[Div(start, class=clear)]][[Div(end)]]
332
333 Boundary conditions to treat the effects of (surface states have been developed. Direct and exchange interactions and interactions with electromagnetic fields can be computed in a post-processing approach based on the NEMO 3-D single particle states.
334
335 Exercises:
336
337 * [[Resource(450)]]
338
339 * [[Resource(2925)]]
340
341
342 == Collection of tools that comprise ACUTE ==
343
344 [[Resource(4826)]]
345
346 [[Resource(3847)]]
347
348 [[Resource(1308)]]
349
350 [[Resource(941)]]
351
352 [[Resource(4438)]]
353
354 [[Resource(1092)]]
355
356 [[Resource(221)]]
357
358 [[Resource(5203)]]
359
360 [[Resource(1305)]]
361
362 [[Resource(450)]]

nanoHUB.org, a resource for nanoscience and nanotechnology, is supported by the National Science Foundation and other funding agencies. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.