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Film Deposition: Dielectric, Polysilicon and Metallization
Published in Kumar Shubham, Ankaj Gupta, Integrated Circuit Fabrication, 2021
Polycrystalline silicon better known as poly-silicon is used as a gate electrode material in MOS devices, a conducting material for multi-level metallization and a contact material for devices having shallow junctions. Poly-silicon can be undoped or doped with elements such as As, P, or B to reduce the resistivity. The dopant can be incorporated in-situ during deposition, or later by diffusion or ion implantation. Polysilicon consisting of several percent oxygen is a semi-insulating material for circuit passivation.
Review of Solid State Physics
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
Dopant impurities are often added to a semiconductor to control its electrical properties. Dopants that add excess electrons to the chemical binding are called donors, because they need only a slight amount of thermal energy to transfer these excess electrons into the conduction band. Dopants that lack an electron to complete the valence bonding are called acceptors, because they need only a slight amount of energy to accept electrons from the valence band into their unfilled states. The simplified energy band structures for intrinsic, n-type, and p-type materials are depicted in Fig. 12.43. The concentration of donor atoms is denoted by ND with energy level ED, and the concentration of acceptor atoms is denoted by NA with energy level EA. If donors are added to the semiconductor, then the concentration of holes is reduced. The opposite occurs if acceptors are added to the semiconductor. Because dopants are generally used in such a small concentration that the energy band structure is unaffected, the general relationship between the free electron concentration and the free hole concentration is given by Eq. (12.131).
Formulation and Classification of Electronic Devices
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
Doping literally means adding impurities to something that is intrinsically pure. In the case of semiconductor, for example, doping is used purposefully for modulating its electrical properties. The impurities used are dependent upon the type of semiconductor. The most common dopants used to dope silicon (Si) (of n-type semiconductor, see Figure 1.15a), are phosphorus (P) or arsenic (As).
A Compact Electrical Modelling for Top-Gated Doped Graphene Field-Effect Transistor
Published in IETE Journal of Research, 2018
Abhishek Kumar Upadhyay, Nitesh Chauhan, S. K. Vishvakarma
We use the value of doping concentration from [7] that gives the values of bandgap for different concentration of doping for three different isomers. The doping concentration (Nf) is given as a percentage of dopant atoms to total atoms in the structure. But for our calculations, we require Nf in the standard form, i.e. in terms of no atoms/cm2 which can be calculated by simple geometry and menstruation. To get the required Nf, we first calculate Nf as the no of atoms per angstrom square (atoms/Å2) by dividing the no of dopants by the sum of the areas of individual hexagons, in Å2, which is calculated using individual bond length of every hexagonal structure's data as given in the said paper. We then change it into the no of atoms/cm2 which is Nf in the standard form. Also, the values of Nf were calculated for different doping concentrations as well as different doping structures. For configuration b, with 12% B doping, we get the highest Nf value of 7.38 × 1014 cm−2 corresponding to a bandgap of 0.72 eV.
Recent developments of doped g-C3N4 photocatalysts for the degradation of organic pollutants
Published in Critical Reviews in Environmental Science and Technology, 2021
Xiaolu Liu, Ran Ma, Li Zhuang, Baowei Hu, Jianrong Chen, Xiaoyan Liu, Xiangke Wang
As a n-type nonmetal semiconductor, nonmetal element doping could continue the metal-free character of g-C3N4. Additionally, due to the existence of high ionization energies and high electronegativity of nonmetals, they can easily form covalent bonds with other compounds by gaining electrons during reaction process (Lin, Li, et al., 2015). Usually, nonmetal introduction will break the symmetry of g-C3N4 and result faster separation speed of electron-hole pairs (Huang et al., 2015). The doping of various nonmetallic g-C3N4 are summarized in Table 1. The nonmetallic dopants include oxygen, phosphorus, sulfur, carbon, halogen, nitrogen and boron.
Excited state dynamics in a sodium and iodine co-doped lead telluride nanowire
Published in Molecular Physics, 2021
Kevin Gima, Talgat M. Inerbaev, D. S. Kilin
This work is based on understanding of the charge balancing of dopants in the doping process. Doping is the process of inserting impurities into a semiconductor to modify its properties. For instance, sodium doping works as follows: