Semiconductor Devices

10 Key excerpts on "Semiconductor Devices"

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  eBook - ePub

  The Fundamentals of Electrical Engineering

  • Felix Hüning(Author)
  • 2014(Publication Date)
  • De Gruyter Oldenbourg

    (Publisher)

  11 Semiconductor Devices

  Basic elements like resistors, capacitors or inductors are part of almost every electronic circuit. But besides these elements in particular Semiconductor Devices are extremely important to realize any complex electronic circuit. Semiconductors are used for devices like diodes or transistors as well as for rather complex integrated circuits (IC) like microprocessors and microcontrollers. These devices in general make use of the properties of doped semiconductors and combine n- and p-doped semiconductors and metals to realize different functionalities.

  The basis for most Semiconductor Devices is pure silicon and compound semiconductors like SiC or GaN to some extent. Highly sophisticated processes are used to produce these Semiconductor Devices in the form of small rectangular dies. Depending on the functionality of the device (MOSFET, microprocessor, etc.) different process technologies are used, but to some extent these techniques are rather similar. The semiconductor industry is highly innovative in order to continuously improve their technologies. In particular semiconductor structures have shrunk very rapidly. According to Moore’s law the number of transistor elements per area doubles every 12–24 months.

  The starting point for silicon dies, or chips is an extremely pure (>99,99999999 % purity) and crystallographically very well defined (very few crystal defects) cylindrical tube of silicon called an ingot. The diameter of the ingots ranges from 100–400 mm. From the ingot thin plates of silicon of some hundred micrometers thickness are cut. The surface of each wafer is separated into small rectangular areas known as dies. Dedicated process steps like photolithography, ion implantation for n- and p-doping, chemical etching, oxidation or vapor deposition are used repetitively to produce the required structures and elements onto the wafer. Small structures of the elements like the gate length of the transistors are is just about 20 nm in 2014! Up to several billion transistors on one die of some cm2

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  Introduction to Microelectronics to Nanoelectronics

  Design and Technology

  • Manoj Kumar Majumder, Vijay Rao Kumbhare, Aditya Japa, Brajesh Kumar Kaushik(Authors)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  1 Semiconductor Physics and Devices

  1.1 Introduction

  Semiconductors have revolutionized the field of electronics and play a prominent role in our day-to-day life. The seed of development of these modern solid-state semiconductors dates back to early 1930s. Each electronic device that we see around is made up of semiconductors. We wouldn’t have been able to achieve these remarkable results without them.

  1.1.1 Conduction in Solids

  The form in which matter exists is called the state of matter. Matter exists in many distinct states of which three states are well known and important. They are solids, liquids, and gases, and other states include plasma, Bose–Einstein condensates, degenerate matter, photonic matter, etc. These other states occur only in extreme conditions of pressure, temperature, and energy. The main difference in the structure of each state lies in the densities of the particles. The density of particles is highest in solids and lowest in gases. Figure 1.1 shows the alignment of particles in different states of matter and the processes through which we can convert one state of matter to another.

  FIGURE 1.1

  Alignment of particles in different states of matter.

  Solids are further classified into three types based upon the distance between their valence band and conduction band. This distance is called the bandgap [1 ]. The electrical conductivity of the substance depends upon the bandgap of the material. We say that the substance is able to conduct if there are free electrons in the conduction band. When energy is supplied to the elements, the electrons in the valence band get excited and jump up into the conduction band, allowing the passage of electricity through the substance. In conductive materials, no bandgap exists, due to which electrons can move easily between their valence band and the conduction band. Unlike conductors, insulators have a huge bandgap between the conduction and the valence band. The valence band remains full since no movement of electrons occurs, and as a result, the conduction band remains empty as well. In semiconductor materials, the bandgap between the conduction band and the valence band is smaller. At room temperature, there is enough energy accessible to displace a few electrons from the valence band into the conduction band. As temperature increases, the conductivity of a semiconductor material increases. Figure 1.2

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  Nanotechnology for Microelectronics and Photonics

  • Raúl José Martín-Palma, José Martínez-Duart(Authors)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 3 Review of Semiconductor Physics Abstract The technology of semiconductors exploded after the development of the transistor, followed by the invention of the integrated circuit and the microchip. As such, semiconductors are ubiquitous in our everyday lives, in part, because Semiconductor Devices have been found to be highly economical because of their miniaturization and reliability. Applications of semiconductors include transistors, diodes, microwave generators, solar cells, lasers, light-emitting diodes, thermistors, charge-coupled devices, and photodetectors, among others. In this chapter the key physical properties of bulk semiconductors are reviewed, from their band structure to transport and optical processes in these materials. Keywords Acceptor; Bandtail states; Biexciton; Degenerate semiconductor; Donor; Dopant; Law of mass action 3.1. Introduction We review in this chapter the physics of bulk semiconductors, which is needed for the understanding of the behavior of low-dimensional semiconductors in mesoscopic systems (Chapters 4 and 5). We will focus mainly on those electronic and optical properties related to the understanding of device applications such as transistors and lasers. The chapter starts with a description of the band structure of typical semiconductors. Next, the calculation of electron and hole concentrations in intrinsic and extrinsic semiconductors is presented. The mechanism of electron transport in semiconductors, both under the action of electric fields and carrier concentration gradients, is also revised. Generation and recombination of carriers in electric fields and under concentration gradients lead to the continuity equation and to such concepts as minority carrier lifetime and diffusion length

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  Understanding Solid State Physics

  • Sharon Ann Holgate(Author)
  • 2021(Publication Date)
  • CRC Press

    (Publisher)

  7 Chips with Everything Semiconductor Devices and Dielectrics

  7.1 Introduction to Semiconductor Devices

  Imagine for a moment a world without any electronic equipment. In this hypothetical world, there would be no mobile phones, no computers, no games consoles, no microwave ovens, and a complete absence of a host of other electronic gadgets that we tend to take for granted. This imaginary life would be our reality if it had not been for the invention of the transistor in 1947 by American physicists John Bardeen (1908–1991), Walter Brattain (1902–1987), and William Shockley (1910–1989), coupled with an increasing understanding of the properties of semiconductor materials.

  The transistor, and almost every other electronic component, is made mainly from semiconductor materials, including silicon (Si), germanium (Ge)—from which many of the first electronic devices were made—and gallium arsenide (GaAs). The most widely used of these is silicon, as many electronic components contain silicon, and almost all integrated circuits are mounted on silicon chips. Silicon occurs naturally as silica (also known as silicon dioxide) in several different forms including quartz and sand. Unlike many of the Earth’s resources, silicon is so abundant that it is unlikely to become used up. This is good news, as the semiconductor industry is one of the biggest industries in the world and more and more high-tech products come on the market each year.

  In this chapter, we will see how some of the most common electronic devices work, what they tend to be made from, and how they are manufactured. We will also discuss insulating materials, which, as we will discover, play an important role in Semiconductor Devices.

  7.1.1 p-n Junctions

  Forming a p-n Junction

  If a layer of p-type semiconductor is sandwiched next to a layer of n-type semiconductor, a p-n junction is formed. As Section 6.4.1 explained, both p-type and n-type semiconductors are electrically neutral overall, since intrinsic semiconductors are electrically neutral, and so are any dopant atoms. So before they are joined together, the p-type and n-type sides of a p-n junction are electrically neutral, but there is a large concentration of electrons in the n-type material and a large concentration of holes in the p-type material. Figure 7.1a shows band diagrams for isolated n-type and p-type materials. The Fermi energy is near to the valence band in the p-type semiconductor, and near to the conduction band in the n-type semiconductor because in both cases, there is a high dopant concentration. (Figure 6.25

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  Engineering Materials Science

  • Milton Ohring(Author)
  • 1995(Publication Date)
  • Academic Press

    (Publisher)

  12 SEMICONDUCTOR MATERIALS AND DEVICES: SCIENCE AND TECHNOLOGY 12.1 INTRODUCTION Semiconductors are a unique class of materials that have transformed society and technology in truly revolutionary ways. A reasonably large number of different semiconductor materials are used in assorted electronic and electro-optical devices. They are broadly divided into elemental and compound semiconductors. The relevant portion of the Periodic Table for these materials is indicated in Fig. 12-1. Elemental semiconductors stem from column IVA and notably include silicon, the most important of all semiconductors. In addition, there is germanium, the first semiconductor to be widely exploited in devices. Today, Ge has been virtually entirely supplanted by Si. Carbon in the form of diamond is also semiconducting. Diamond’s semiconducting properties have not yet been capitalized upon, but its remarkably high thermal conductivity has been used to draw heat away from semiconductor lasers, enabling them to operate more reliably. FIGURE 12-1 Elements of the Periodic Table that play an important role in semiconductor technology. Compound semiconductors are composed of elements drawn almost entirely from four columns of the Periodic Table, with two residing on one side next to column IVA and two adjacent to it on the other side. Columns IIB and IIIA, containing metals with nominal valences of 2 and 3, respectively, thus combine with the nonmetals of columns VA and VIA that have respective valences of 5 and 6. Important elemental and binary semiconductor materials are listed in Table 12-1, together with a complement of physical and electrical properties whose meanings will become clearer as the chapter develops. It is interesting to note that the compounds are either of the III–V type (e.g., GaAs, InP) or the II–VI type (e.g., CdTe, ZnS). Thus, eight electrons are available (3 + 5 = 8 or 2 + 6 = 8) to be shared by the atoms

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  Electronic Materials

  Principles and Applied Science

  • Yuriy M. Poplavko(Author)
  • 2018(Publication Date)
  • Elsevier

    (Publisher)

  exponential increase in electrical conductivity with temperature rise. Near absolute zero semiconductors are close to insulators.
• 2.  
  Semiconductors are crystals with a bandgap in electronic spectrum, which is in the range of 0.1–2.5 electron-volts. For example, gallium arsenide can be grouped under wide-gap semiconductors, while indium arsenide is a narrow-gap semiconductor. Among semiconductors there are some chemical elements (germanium, silicon, selenium, tellurium, arsenic, etc.), several alloys, and compounds. Almost all inorganic materials of the surrounding world are semiconductors. In nature, the most common semiconductor is silicon that occupies almost 30 percent of the earth's crust.
• 3.  
  Semiconductors have conducting as well as dielectric properties. In semiconductor crystals, atoms are usually joined by covalent bonds (i.e., pair of electrons bounded with two atoms); these electrons require a certain level of internal energy to release from atom that characterize the difference between semiconductors and dielectrics. This energy can be applied by energy fluctuations in crystal (room temperature thermal energy level is 0.026 eV).
• 4.  
  The analysis of Schrodinger equation for electrons in crystal (Bloch theorem) shows that electronic wave function depends on the wave vector k that module has a dimension of inverse length; by this way, the quasi-impulse p  = ħk can be introduced in a consideration. This concept is very useful for examining many problems in electronic theory of solids.
• 5.  
  In crystalline semiconductors, spatial atomic structure has long-range ordering, that is, the position of individual atoms (or groups of atoms) is repeated periodically within volume of crystal. Accordingly, the potential field is periodically changed with distance, divisible to period of structure. The compact recording of this condition is: U (r ) = U (r + na ), where a is period of structure and n