1. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith CRYSTAL STRUCTURES LECTURE 5 (18 slides)

2. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith xy z  up Constructing an FCC crystal lattice Note how the FCC is justifiably called cubic close-packed (CCP).

3. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith x y z  up Homework 5: A base 2-D close-packed square lattice can be found in the both the SC and FCC lattices. The 3-D extension differs, Resulting in a close-packed cubic lattice for FCC but a much less Dense SC layout. BCC is also not close-packed. Can you find, in any plane of the BCC lattice, a 2D close-packed structure? Discuss the (111) plane in this regard. What is the plane that looks closest to the one below? x y

4. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Building an FCC lattice in an obvious way First layerSecond layerThird layer Note: certain planes clearly show HCP patterns. HOME: what plane is this?

5. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Diamond and Zincblende Lattices 8-atom unit cell made from FCC 4-atom unit cell by putting another atom at a/4+b/4+c/4 from each FCC atom FCC Zincblende lattice has different species in FCC sublattices: e.g. InP, GaAs

6. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Analyzing the diamond lattice FCC BCC Conclusion: the octant shown is an incomplete BCC lattice pattern. Use this in one of the HW’s Regarding packing fraction Note: 4 bonds helps explain that C forms a diamond lattice structure

7. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Our favorite nine III-V binary semiconductors form zincblende lattices As Ga Basic FCC lattice of Ga FCC lattice for As

8. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Again, thanks to some popsicle sticks, some Elmer’s glue and a bunch of Marbles from Michael’s Arts and Crafts Store, a digital camera and Photoshop software HCP starting plane – builds up, but at each plane, one can choose different sites for the triad – as shown above Hexagonal Close Packing

9. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith HCP and FCC contain HCP-type planes Hexagonal Close-Packed Cubic (FCC) Close-Packed Top view In fact, these lattice types have the same packing fraction. Open (seen from above) all layersClosed within 3 layers

10. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Crystalline Element Lattice Types Reference: http://www.uis.edu/~trammel/sci/unit_cells/sld30.htm IIIIVVVI II VII BCC has 8 nearest neighbors diamond lattices HCP has 12 nearest neighbors

11. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Streetman and Banerjee 6)1.4 7)1.7 8)1.10 9)1.14 Assigned Problems 5-8.

12. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith CRYSTAL GROWTH

13. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Czolchraski Crystal Growth Method Ref: S&B Figs. 1.10,1.11 12” diameter by 1 meter Si boule Made by pulling seed from Si melt seed

14. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Epitaxial Growth Methods LPE (Liquid Phase Epitaxy) – precipitation from liquid phase onto substrate, controlled by time and temperature VPE (Vapor Phase Epitaxy) – fast gas flow velocity over heated substrates; surface reaction of compounds releases desired atoms MBE (Molecular Beam Epitaxy) – for monolayer-level control of stoichiometry – beams of elements to be deposited Reference: Mandatory reading (hand out): E. D. Jungbluth, “Crystal Growth Methods Shape Communications Lasers,” Laser Focus World, vol. 29, pp. 61-72 (Feb., 1993). Start with suitably oriented crystal substrate – grow layers of identical (homoepitaxy) or different material (heteroepitaxy) maintaining lattice type, orientation and lattice constant.

15. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Epitaxial Growth Technologies Reference: Mandatory reading (will hand out): E. D. Jungbluth, “Crystal Growth Methods Shape Communications Lasers,” Laser Focus World, vol. 29, pp. 61-72 (Feb., 1993). LPE VPE MBE

16. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Epitaxial Growth Methods 2” dia wafer cassette InP-based laser substrate Reference: E. D. Jungbluth, ibid. Reference: G. P. Agrawal 2-D Lithography and etching at these stages

17. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith A superlattice of MBE-Grown Layers Ref: S&B Fig. 1.16 Alternating layers of GaAs (dark) and AlAs (light) with 4-monolayer periodicity: SUPERLATTICE CB VB

18. Semiconductor Electronic Devices EECS 321 Spring 2002 CWRUProf. Dave Smith Assignment 10. Read. E. D. Jungbluth, “Crystal Growth Methods Shape Communications Lasers,” Laser Focus World, vol. 29, pp. 61-72 (Feb., 1993). a) What is an acceptable substrate defect density? b) How would you hook up a DC battery to make Jungbluth’s Fig 1’s device lase? How would you convert it into a detector instead? c) Compare substrate heating techniques in the cases of LPE, VPE and MBE. d) Several different bandgap-engineered devices types are mentioned and they are more suitable for some techniques than others. Name one type suitable for each fab method and why is that method preferred? E.g.: use the figure right bottom.