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Si. As, a Group V element, introduces conduction electrons and creates N-type silicon, and is called a donor. B, a Group III element, introduces holes and creates P-type silicon, and is called an acceptor. Donors and acceptors are known m0 q4 as dopants. Dopant ionization Hydrogen: E ion = = 13.6 eV 8e energy ~50meV (very low). 0 2h2.
Figure 4: Band gap structure of an intrinsic semiconductor. (a) Schematic band diagram, (b) density of states g(E), (c) Fermi distribution function f(E), (d) carrier concentration ne(E) and nh(E). Ec, Ev and Ef represent the conduction band energy, valence band energy and Fermi energy level, respectively. of the conduction band, ne = ∫ 1 Ec g ...
Most semiconductor materials are single crystals. Figure 1.2 exhibits three cubic-crystal unit cells - simple cubic, body-centered cubic, and face-centered cubic. The element semiconductors, silicon and germanium, have a diamond lattice structure as shown in Figure 1.3.
Actual 3D Structure of a Silicon Crystal Lattice. Each Silicon atom is surrounded by 4 other Silicon atoms in a tetrahedral configuration. Silicon atomic density = 5x1022 cm-3. ECE 315 – Spring 2005 – Farhan Rana – Cornell University.
Each silicon atom is surrounded by four nearest neighb ors as illustrated by the shaded cluster in Fig. 1–2. We can represent the silicon crystal structure with the two-dimensional drawing shown in Fig. 1–4. An Si atom is connected to each neighbor with two dots representing the two shared electrons in the covalent bond. Figure 1–4
The most commonly used semiconductor is silicon or Si. In a Si crystal each Si atom forms a covalent bond with 4 other Si atoms. Si has 4 electrons in its valence (or outer most shell) and therefore it can bond with 4 other Si atoms. A cartoon depiction of Si crystal is then as shown in the Figure.
Gallium arsenide, germanium, and silicon are some of the most commonly used semiconductors. Silicon is used in electronic circuit fabrication and gallium arsenide is used in solar cells, laser diodes, etc. Types of Semiconductors Semiconductors can be classified as: Intrinsic Semiconductor Extrinsic Semiconductor
