E E 339 - CN16-heterojunctions

E E 339 - CN16-heterojunctions - Heterojunctions 1 Outline...

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1 Heterojunctions 1 Definition and varieties Obtaining the equilibrium band diagram (quick discussion Outline discussion) Summary 2
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2 Heterojunctions ” are formed between different semiconductor materials (vs. “ Homojunctions ” in homogeneous materials) … … not necessarily lattice matched but generally with layer thicknesses kept below the critical thickness Heterojunctions: definition and flavors thicknesses kept below the critical thickness. Because the bandstructure, in addition to doping, can vary across the junction there are more possible types of junctions than in homogeneous materials. E.g., could form a “Pn straddling gap heterojunction,” where the capital letter indicates which material has the larger bandgap and “straddling,” indicates relative band offsets: Figure 5—45, modified a p-type, wide band gap semiconductor an n-type narrower band gap semiconductor, “prior” to junction formation. 3 There are three basic types of heterointerfaces : “straddling gap” (“Type I ”) … where, as a consequence, electrons and holes tend to be E c x E v E e h localized on the same side of the interface, “staggered gap” (“Type II ”) localized to oppositie sides of the interface, and h e “broken gap” (“Type III ” ) where electrons move freely between the valence band of one material and the conduction band of the other.
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E E 339 - CN16-heterojunctions - Heterojunctions 1 Outline...

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