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The crystal structure of the III-V semiconductors

The crystal structure of the III-V semiconductors. Diamond and Zincblende Lattices.

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The crystal structure of the III-V semiconductors

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  1. The crystal structure of the III-V semiconductors Diamond and Zincblende Lattices Unit cells for silicon (Si) and gallium arsenide (GaAs) Silicon - diamond lattice GaAs - zincblende (cubic zinc sulfide) lattice (most other III-V and many II-VI semiconductors have zincblende lattice)Diamond and zincblende lattice based on tetragonal pattern of bonds from each atom to nearest neighbors-two interlocking facecentered- cubic lattices lattice parameter (or constant), a- repeat length of the unit cells e. g., GaAs, a = 5.65 Å (Angstroms) = 0.565 nm.

  2. The band structure ?

  3. One relevant conduction band is formed from S- like atomic orbitals “unit cell” part of wavefunction is approximately spherically symmetric. The three upper valence bands are formed from (three) P- like orbitals and the spin-orbit interaction splits off lowest, “split-off” hole (i. e., valence) band. The remaining two hole bands have the same energy (“degenerate”) at zone center, but their curvature is different, forming a “heavy hole” (hh) band (broad), and a “light hole” (lh) band (narrower) First Brillouin zone E vs. k banddiagram of zincblende semiconductors

  4. Compound Semiconductors (alloys) For optoelectronics, most devices are fabricated of“compound semiconductors” particularly III-V materials made from •Group III (Al, Ga, In) and •Group V (N, P, As, Sb) elements •Sometimes Si and Ge (Group IV) are used as photodetectors •Sometimes II-VI (e.g. ZnSe) and IV-VI materials (e.g., PbTe) Alloys of compound semiconductors used extensively to adjust the basic materials properties, e.g., lattice constant, bandgap,refractive index, optical emission or detection wavelength EXAMPLE – InxGa1- xAs (where x is the mole fraction of indium) InxGa1- xAs is not strictly crystalline because not every unit cell is identical (random III site location), but we treat such alloys as crystalline to a first approximation

  5. The Human eye response Lasers and LEDs for displays or lighting must emit in the 430-670 nm wavelength region (bandgaps of 3.0-1.9 eV).

  6. Technologically Available Materials

  7. Some of the applacations Large Area, Full Color Displays LED Traffic Lights

  8. the first principles calculationguess first compare charge convergence new

  9. Empirical tight binding Hv= < |Hv-ESv|= 0

  10. The Hamiltonian in sp3d2

  11. The equation came from ETB

  12. Volume optimization for InN by wien2K

  13. Volume optimization for InAs by wien2K

  14. Volume optimization for InSb by wien2K

  15. Band structure of InN by wien2k

  16. Band structure of InAs by wien2k

  17. Band structure of InSb by wien2k

  18. Band structure of InN by ETB

  19. Density of states for InN

  20. Band structure of InAs by ETB

  21. Density of states for InAs

  22. Band structure of InSb by ETB

  23. Density of states for InSb

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