Bandstructure Lab uses the sp3s*d5 tight binding method to compute E(k) for bulk, planar, and nanowire semiconductors. Using this tool, you can quickly compute and visualize the bandstructures of bulk semiconductors, thin films, and nanowires for various materials, growth orientations, and strain conditions. Physical parameters such as the bandgap and effective mass can also be obtained from the computed E(k). The bandedges and effective masses of the bulk materials and the nanostructures structures can be analyzed as a function of various strain conditions. As explained in a related seminar, correct band structure is essential for modeling devices at the nano scale.

• Chapter 5 of Quantum Transport by S. Datta (Cambridge, 2005)

Starting from version 2.0, the tool is now powered by a C code named OMEN. All previous versions were coded in Matlab. Version 2.0 is a radical new release of the code and we are aware of several issues that are not fully stable. We very much appreciate feedback if certain features of the tool do not function properly. The last 1.X version of Bandstructure Lab is still available at the following link: Bandstructure Lab Version 1.2 (published). Phyiscal Limitations:

• Different Tight-binding models can give different electron and hole effective masses. This happens since different band models give different curvatures.Always a higher and more sophisticated band model will give better estimation of effective masses. Eg: sp3d5s* TB models give better estimate of effective mass compared to sp3s* TB models.

Known issues with Version 2.0:

• bulk effective mass table is not correct for light, and heavy hole bands
• charge self-consistent calculation appears to be unstable for some devices
• nanowire dimensions exceeding 5-6nm in diameter appear to crash the simulations. More work is needed in the tool

Tool Versions

• 2.0.1: Bug Fixes :
  • Strain sweep now provides correct band edges as well as effective mass values for bulk.
• 2.0.1 New Features: Following new features will be available in the next release of the tool:
  • Transport effective masses for nanowires and UTB devices.
  • Self-consistent run for nanowire Gate all around FETs and DGMOS.
• 2.0.2 Bugfixes:
  • Bulk effective masses for light, and heavy hole bands have been corrected.
  • Charge self-consistent simulations are now stable.
  • Biaxial strain sweep related error has been removed. Now all the results appear that have completed.(Answer to the biaxial question too.)
• 2.0.2 New Features :
  • Transport effective masses for nanowires and UTB devices are now available.
  • Now 3D EK simulation data available with 3D bulk simulation as data file. (Answer to this question .
  • Self-consistent run for 1 gate bias now possible for Gate all around nanowire FETs and DGMOS.
• 2.0.3 New Features
  • Parallel execution on 24 cores in an instant-on parallel computing environment where appropriate. Used for nanowires and ultra-thin bodies with not too large cross section.

Wish List:

• Allow other types of crystals and new materials to be simulated to obtain bandstructure.
• Allow other bandstructure calculation like k.p.

Collaboration: Simulation of larger structures and new materials can be done on collaborative basis. We would like to know what you want to achieve and we can work towards it. Please feel free to contact the developers of the tool.

1. nanoelectronics