Zero bandgap semiconductor

It is interesting to point out that, graphene is a zero-bandgap semiconductor with infinite exciton Bohr diameter such that confinement can be observed in any fragment. However, GQDs typically have dimensions in the... 

Figure 2 shows the energy band diagram of a direct bandgap semiconductor where is lower in energy than Ex, and spontaneous emission of a photon is the most likely path for recombination. In Fig. 2, the F valley of the conduction band is directly above the holes where the momentum change in the transition is nearly zero. Electrons in the X valley of the conduction band have a different momentum and thus cannot directly recombine with... 

Graphite is an example of a zero-bandgap pol)mer whose behavior is metal-like. Most pol)mers behave more like semiconductors and require doping to achieve high conductivity (see Chapter 20 for more details). 

In a manner analogous to confining the movement of an electron to a two-dimensional plane as in a quantum well structure, additional confinement conditions can also be imposed to realize confinement in both one and zero dimensions, to generate quantum wire and quantum dot structures (see Fig. 7). These structures can be realized physically by having a semiconductor material take on the form of an ultrasmall rectangular-shaped wire or an ultrasmall box, where the surrounding material is another semiconductor material of wider bandgap. For the quantum wire structure, the wire acts as a potential well that... 

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