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handout12 - Handout 12 Energy Bands in Group IV and III-V...

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1 ECE 407 – Spring 2009 – Farhan Rana – Cornell University Handout 12 Energy Bands in Group IV and III-V Semiconductors In this lecture you will learn: • The tight binding method (contd…) • The energy bands in group IV and group III-V semiconductors with FCC lattice structure ECE 407 – Spring 2009 – Farhan Rana – Cornell University FCC Lattice: A Review a a a 1 a r 2 a r 3 a r () z y a a ˆ ˆ 2 1 + = r z x a a ˆ ˆ 2 2 + = r y x a a ˆ ˆ 2 3 + = r Face Centered Cubic (FCC) Lattice: x y z Unit Cell Most group VI and group III-V semiconductor, such as Si, Ge, GaAs, InP, etc have FCC lattices with a two-atom basis
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2 ECE 407 – Spring 2009 – Farhan Rana – Cornell University Lattices of Group IV Semiconductors (Silicon, Germanium, and Diamond) • The underlying lattice is an FCC lattice with a two-point (or two-atom) basis. • Each atom is covalently bonded to four other atoms (and vice versa) via sp3 bonds in a tetrahedral configuration Diamond lattice (Si, Ge, and Diamond) x y z () 1 , 1 , 1 4 1 a n = r 1 , 1 , 1 4 2 = a n r 1 , 1 , 1 4 3 = a n r 1 , 1 , 1 4 4 = a n r Nearest neighbor vectors 1 n r 2 n r 3 n r 4 n r Basis vectors 0 1 = d r 1 , 1 , 1 4 2 a d = r ECE 407 – Spring 2009 – Farhan Rana – Cornell University Lattices of III-V Binaries (GaAs, InP, InAs, AlAs, InSb, etc) • The underlying lattice is an FCC lattice with a two-point (or two-atom) basis. In contrast to the diamond lattice, the two atoms in the basis of zincblende lattice are different – one belongs to group III and one belongs to group V • Each Group III atom is covalently bonded to four other group V atoms (and vice
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handout12 - Handout 12 Energy Bands in Group IV and III-V...

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