(a) An intrinsic semiconductor is an insulator having a complete electron shell. Alternatively, an exciton may be described as an excited state of an atom, ion, or molecule, if the excitation is wandering from one cell of the lattice to another. Electrons and holes are created by excitation of electron from valence band to the conduction band. This electron is free for conduction about the crystal lattice. (b) However, thermal energy can create few electron-hole pairs resulting in weak conduction. The formation of multiple electron–hole pairs per absorbed photon in photoexcited bulk semiconductors is a process typically explained by impact ionization (I.I.). In the semiconductor, free charge carriers are electrons and electron holes (electron-hole pairs). Term (Index): Definition: electron-hole pair : whenever electron acquires energy sufficient to "move" from the valence band to the conductiorn band a free hole is created in the valence band, and hence, electron-hole pair is generated; when electron and hole recombine, electron-hole pair is anihilated. An electron hole (often simply called a hole) is the lack of an electron at a position where one could exist in an atom or atomic lattice. Therefore, it is evident that the number of electrons and holes will be equal because for each electron that escapes from an atom an empty place -a hole- … At absolute zero temperature intrinsic semiconductor behaves as insulator. For an electron trap, the energy required for an electron to occupy that energy state is significantly higher than the chance for a hole to occupy said state (Eqn.3). Atomic and molecular excitons. Electron is a negative charge carrier whereas hole is a positive charge carrier. From this, it seems that holes are simply lack of electrons that are given enough (thermal) energy to escape from a particular atom. The converse is true for a hole trap (Eqn.4). Electrons and holes are created by excitation of electron from valence band to the conduction band. - Due to the electron that raised to the conduction band by external energy, one hole left in the valence band and it will create electron-hole pair b) Name the two energy bands at which current (electron current and hole current) is produced in silicon. An electron hole pair consists of an electron (It occurs, when a crystall in ground state absorbs energy and gets into an excited state) and a defectelectron. 1.3 Current in Semiconductor a) What is an electron-hole pair? In the semiconductor, free charge carriers are electrons and electron holes (electron-hole pairs). In this process, an electron or hole with kinetic energy greater than the semiconductor bandgap produces one or more additional electron–hole pairs. However, at room temperature the electrons present in the outermost orbit absorb thermal energy. The probabilities for electron occupation and hole occupation are represented by equations one and two respectively. These electron-hole pairs can only move along the surface. An electron hole (often simply called a hole) is the lack of an electron at a position where one could exist in an atom or atomic lattice. Thermal energy may occasionally free an electron from the crystal lattice as in Figure above (b). 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