{"id":26462,"date":"2020-02-20T11:35:47","date_gmt":"2020-02-20T11:35:47","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=26462"},"modified":"2023-07-11T10:01:22","modified_gmt":"2023-07-11T10:01:22","slug":"types-of-semiconductors","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/types-of-semiconductors\/","title":{"rendered":"Types of Semiconductors"},"content":{"rendered":"<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<figure id=\"attachment_26115\" aria-describedby=\"caption-attachment-26115\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-strip-detector-semiconductors.png\"><img loading=\"lazy\" class=\"size-medium wp-image-26115\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-strip-detector-semiconductors-300x197.png\" alt=\"silicon strip detector - semiconductors\" width=\"300\" height=\"197\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-strip-detector-semiconductors-300x197.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-strip-detector-semiconductors.png 736w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26115\" class=\"wp-caption-text\">Silicin Strip Detector Source: micronsemiconductor.co.uk<\/figcaption><\/figure>\n<p>In general, <strong>semiconductors<\/strong> are inorganic or organic materials that can control their conduction depending on chemical structure, temperature, illumination, and the presence of dopants. The name <strong>semiconductor<\/strong> comes from the fact that these materials have <strong>electrical conductivity<\/strong> between a metal, like copper, gold, etc., and an insulator, like glass. They have an <strong>energy gap<\/strong> of less than 4eV (about 1eV). In solid-state physics, this energy gap or band gap is an energy range between the <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/conduction-and-valence-band-in-semiconductors\/\">valence band and conduction band<\/a> where electron states are forbidden. In contrast to conductors, semiconductors\u2019 electrons must obtain energy (e.g., from ionizing radiation) to cross the band gap and reach the conduction band. <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/\"><strong>Properties of semiconductors<\/strong><\/a> are determined by the energy gap between valence and conduction bands.<\/p>\n<h2>Types of Semiconductors<\/h2>\n<h3>Semiconductor Materials<\/h3>\n<p>There are many <strong>types of semiconductors<\/strong> in nature and others synthesized in laboratories; however, the best known are silicon (Si) and germanium (Ge).<\/p>\n<p><strong>Types of semiconductors:<\/strong><\/p>\n<ul>\n<li>\n<figure id=\"attachment_26466\" aria-describedby=\"caption-attachment-26466\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-26466\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material-300x209.jpg\" alt=\"silicon - semiconducting material\" width=\"300\" height=\"209\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material-300x209.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material-768x534.jpg 768w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material-1024x712.jpg 1024w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/silicon-semiconducting-material.jpg 1046w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26466\" class=\"wp-caption-text\">Purified silicon. Source: wikipedia.org License: Public Domain<\/figcaption><\/figure>\n<p><strong>Silicon. Silicon<\/strong> is a chemical element with the <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atomic-nuclear-structure\/atomic-number-proton-number\/\">atomic number<\/a> <strong>14<\/strong>, meaning\u00a0there are 14 protons and 14 electrons in the atomic structure. The <strong>chemical symbol<\/strong> for Silicon is <strong>Si<\/strong>. Silicon is a hard and brittle crystalline solid with a blue-grey metallic luster, and it is a tetravalent metalloid and semiconductor. Silicon is mainly used for charged particle detectors (especially for tracking charged particles) and soft X-ray detectors. The large band-gap energy (Egap= 1.12 eV) allows us to operate the detector at room temperature, but cooling is preferred to reduce noise. Silicon-based detectors are very important in high-energy physics. Since silicon-based detectors are very good for <strong>tracking charged particles<\/strong>, they constitute a substantial part of the detection system at the LHC in CERN.<\/p><\/li>\n<li>\n<figure id=\"attachment_26465\" aria-describedby=\"caption-attachment-26465\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-26465\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material-300x300.jpg\" alt=\"Germanium - semiconductor\" width=\"300\" height=\"300\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material-300x300.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material-150x150.jpg 150w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material-768x768.jpg 768w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/germanium-semiconducting-material.jpg 1024w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26465\" class=\"wp-caption-text\">12 grams polycrystalline germanium. Source: wikipedia.org License: CC BY 3.0<\/figcaption><\/figure>\n<p><strong>Germanium. Germanium<\/strong> is a chemical element with the <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atomic-nuclear-structure\/atomic-number-proton-number\/\">atomic number<\/a> <strong>32,<\/strong> which means there are 32 protons and 32 electrons in the atomic structure. The <strong>chemical symbol<\/strong> for Germanium is <strong>Ge<\/strong>. Germanium is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors, tin and silicon. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Germanium is widely used for <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/gamma-spectroscopy\/\"><strong>gamma-ray spectroscopy<\/strong><\/a>. In gamma spectroscopy, germanium is preferred due to its atomic number being much higher than silicon, increasing the probability of gamma-ray interaction. Germanium is more used than silicon for radiation detection because the average energy necessary to create an <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/electron-hole-pair\/\">electron-hole pair<\/a> is 3.6 eV for silicon and 2.9 eV for germanium, which provides the latter a better resolution in energy. On the other hand, germanium has a small band gap energy (E<sub>gap<\/sub> = 0.67 eV), which requires operating the detector at cryogenic temperatures.<\/p><\/li>\n<li><strong>Diamond<\/strong>. Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamonds are also very good electrical insulators, which are both useful and problematic for electrical devices. Diamond is a wide-bandgap semiconductor (Egap= 5.47 eV) with high potential as an electronic device material in many devices. Diamond detectors have many similarities with silicon detectors but are expected to offer significant advantages, particularly high radiation hardness and very low drift currents.<\/li>\n<li><strong><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/semiconductor-detectors-table-of-parameters.png\"><img loading=\"lazy\" class=\"alignright wp-image-26116\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/semiconductor-detectors-table-of-parameters.png\" alt=\"semiconductor detectors - table of parameters\" width=\"467\" height=\"297\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/semiconductor-detectors-table-of-parameters.png 630w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/semiconductor-detectors-table-of-parameters-300x191.png 300w\" sizes=\"(max-width: 467px) 100vw, 467px\" \/><\/a>CdTe and CdZnTe. <\/strong>Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) are promising semiconductor materials for hard X-ray and gamma-ray detection. These materials\u2019 high atomic number and density mean they can effectively attenuate X-rays and gamma rays with energies greater than 20 keV that traditional silicon-based sensors cannot detect. This significantly increases their quantum efficiency in comparison with silicon-based. The large band-gap energy (Egap= 1.44 eV) allows us to operate the detector at room temperature. On the other hand, a considerable amount of charge loss in these detectors produces a reduced energy resolution.<\/li>\n<\/ul>\n<h2>Intrinsic Semiconductor &#8211; Pure Semiconductor<\/h2>\n<p>An <strong>intrinsic semiconductor<\/strong> is completely pure without any significant dopant species. Therefore, intrinsic semiconductors are also known as pure semiconductors or i-type semiconductors.<\/p>\n<p><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/intrinsic-semiconductor-i-type-semiconductor.png\"><img loading=\"lazy\" class=\"alignright wp-image-26110\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/intrinsic-semiconductor-i-type-semiconductor.png\" alt=\"intrinsic semiconductors\" width=\"500\" height=\"347\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/intrinsic-semiconductor-i-type-semiconductor.png 817w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/intrinsic-semiconductor-i-type-semiconductor-300x208.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/intrinsic-semiconductor-i-type-semiconductor-768x533.png 768w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/a>The number of charge carriers at a certain temperature is therefore determined by the material\u2019s properties instead of the number of impurities. Note that a 1 cm<sup>3<\/sup> sample of pure germanium at 20 \u00b0C contains about 4.2\u00d710<sup>22<\/sup> atoms but also contains about 2.5 x 10<sup>13<\/sup> free electrons and 2.5 x 10<sup>13<\/sup> holes. These charge carriers are produced by thermal excitation. In intrinsic semiconductors, the number of excited electrons and the number of holes are equal: <strong>n = p<\/strong>. Electrons and holes are created by the excitation of electrons from the valence band to the conduction band. An <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/what-is-electron-hole\/\">electron-hole<\/a> (often simply called a hole) is the lack of an electron at a position where one could exist in an atom or atomic lattice. This equality may even be the case after doping the semiconductor, though only if it is doped with both donors and acceptors equally. In this case, n = p still holds, and the semiconductor remains intrinsic, though doped.<\/p>\n<p>Semiconductors have an energy gap of less than 4eV (about 1eV). Band gaps are naturally different for different materials. For example, diamond is a wide-bandgap semiconductor (Egap= 5.47 eV) with high potential as an electronic device material in many devices. On the other side, germanium has a small band gap energy (E<sub>gap<\/sub> = 0.67 eV), which requires operating the detector at cryogenic temperatures. In solid-state physics, this energy gap or band gap is an energy range between the valence band and conduction band where electron states are forbidden. In contrast to conductors, semiconductors\u2019 electrons must obtain energy (e.g., from ionizing radiation) to cross the band gap and reach the conduction band.<\/p>\n<p>Intrinsic semiconductors, however, are not very useful, as they are neither very good insulators nor very good conductors. However, one important feature of semiconductors is that their conductivity can be increased and controlled by <strong>doping<\/strong> with impurities and gating with electric fields. Recall that a 1 cm<sup>3<\/sup> sample of pure germanium at 20 \u00b0C contains about 4.2\u00d710<sup>22<\/sup> atoms but also contains about 2.5 x 10<sup>13<\/sup> free electrons and 2.5 x 10<sup>13<\/sup> holes constantly generated from thermal energy. Total absorption of a 1 MeV photon produces around <strong>3 x 10<sup>5<\/sup> electron-hole pairs<\/strong>. This value is minor compared to the total number of free carriers in a 1 cm<sup>3<\/sup> intrinsic semiconductor. As can be seen, the signal-to-noise ratio (S\/N) would be minimal. Adding 0.001% of arsenic (an impurity) donates an extra 10<sup>17<\/sup> free electrons in the same volume, and the electrical conductivity is increased by a factor of 10,000. The signal-to-noise ratio (S\/N) would be even smaller in doped material. Because germanium has a relatively low band gap, these detectors must be cooled to reduce the thermal generation of charge carriers to an acceptable level. Otherwise, leakage current-induced noise destroys the energy resolution of the detector. Doping and gating move the conduction or valence band much closer to the Fermi level and greatly increase the number of partially filled states.<\/p>\n<h2>Extrinsic Semiconductors &#8211; Doped Semiconductors<\/h2>\n<p>An <strong>extrinsic semiconductor<\/strong>, or <strong>doped semiconductor<\/strong>, is a semiconductor that was <strong>intentionally doped<\/strong> to modulate its electrical, optical, and structural properties. In the case of semiconductor detectors of ionizing radiation, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of changes in their electrical properties. Therefore, intrinsic semiconductors are also known as pure semiconductors or i-type semiconductors.<\/p>\n<p>The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties since these foreign atoms incorporated into the crystal structure of the semiconductor provide <strong>free charge carriers<\/strong> (electrons or electron holes) in the semiconductor. In an extrinsic semiconductor, these foreign dopant atoms in the crystal lattice mainly provide the charge carriers that carry electric current through the crystal. Two types of dopant atoms generally result in two types of extrinsic semiconductors. These dopants that produce the desired controlled changes are classified as either <strong>electron acceptors<\/strong> or <strong>donors,<\/strong> and the corresponding doped semiconductors are known as:<\/p>\n<ul>\n<li><strong>n-type Semiconductors.<\/strong><\/li>\n<li><strong>p-type Semiconductors.<\/strong><\/li>\n<\/ul>\n<p><strong>Extrinsic semiconductors<\/strong> are components of many common electrical devices, as well as many detectors of ionizing radiation. For these purposes, a semiconductor diode (devices that allow current in only one direction) usually consists of p-type and n-type semiconductors placed in a junction with one another.<\/p>\n<h3>n-type Semiconductors<\/h3>\n<p><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-n-type-donor.png\"><img loading=\"lazy\" class=\"alignright wp-image-26109\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-n-type-donor.png\" alt=\"extrinsic - doped semiconductor - n-type - donor\" width=\"501\" height=\"354\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-n-type-donor.png 791w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-n-type-donor-300x212.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-n-type-donor-768x542.png 768w\" sizes=\"(max-width: 501px) 100vw, 501px\" \/><\/a>An extrinsic semiconductor doped with electron donor atoms is called an <strong>n-type semiconductor<\/strong> because most charge carriers in the crystal are negative electrons. Since silicon is a tetravalent element, the normal crystal structure contains 4 covalent bonds from four valence electrons. The most common dopants in silicon are group III and V elements. Group V elements (pentavalent) have five valence electrons, allowing them to act as donors. That means adding these pentavalent impurities such as arsenic, antimony, or phosphorus contributes to free electrons, greatly increasing the conductivity of the intrinsic semiconductor. For example, a silicon crystal doped with boron (group III) creates a p-type semiconductor, whereas a crystal doped with phosphorus (group V) results in an n-type semiconductor.<\/p>\n<p>The conduction electrons are completely dominated by the number of <strong>donor electrons<\/strong>. Therefore:<\/p>\n<p><strong>The total number of conduction electrons is approximately equal to the number of donor sites, n\u2248N<\/strong><strong><sub>D<\/sub><\/strong><strong>. <\/strong><\/p>\n<p>The charge neutrality of semiconductor material is maintained because excited donor sites balance the conduction electrons. The net result is that the number of conduction electrons increases while the number of holes is reduced. The imbalance of the carrier concentration in the respective bands is expressed by the different absolute number of electrons and holes. Electrons are majority carriers, while holes are minority carriers in n-type material.<\/p>\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>Donor Level<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Donor Level<\/strong><\/p>\n<p>From the <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/band-gap-energy-gap\/\">energy gap<\/a> viewpoint, such impurities \u201ccreate\u201d energy levels in the band gap <strong>close to the conduction band<\/strong> so that electrons can be <strong>easily excited<\/strong> from these levels into the conduction band. The electrons are said to be the \u201c<strong>majority carriers<\/strong>\u201d for current flow in an n-type semiconductor. This shifts the effective <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/fermi-level\/\">Fermi level<\/a> to a point about halfway between the donor levels and the conduction band. Fermi level is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. The Fermi level is the surface of the Fermi sea at absolute zero, where no electrons will have enough energy to rise above the surface. In pure semiconductors, the position of the Fermi level is within the band gap, approximately in the middle of the band gap.<\/p>\n<\/div><\/div>\n<h3>p-type Semiconductors<\/h3>\n<p><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-p-type-acceptor.png\"><img loading=\"lazy\" class=\"alignright wp-image-26108\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-p-type-acceptor.png\" alt=\"extrinsic - doped semiconductor - p-type - acceptor\" width=\"499\" height=\"343\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-p-type-acceptor.png 808w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-p-type-acceptor-300x206.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/extrinsic-doped-semiconductor-p-type-acceptor-768x528.png 768w\" sizes=\"(max-width: 499px) 100vw, 499px\" \/><\/a>An <strong>extrinsic semiconductor<\/strong> <strong>doped with electron acceptor<\/strong> atoms is called a <strong>p-type semiconductor<\/strong> because most charge carriers in the crystal are <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/what-is-electron-hole\/\">electron holes<\/a> (positive charge carriers). The pure semiconductor <strong>silicon is a tetravalent element<\/strong>, and the\u00a0normal crystal structure contains 4 covalent bonds from four valence electrons. In silicon, the most common <strong>dopants are group III<\/strong> and <strong>group V elements<\/strong>. Group III elements (trivalent) all contain three valence electrons, causing them to function as acceptors when used to dope silicon. When an acceptor atom replaces a tetravalent silicon atom in the crystal, a vacant state (an electron-hole) is created. 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. It is one of the two charge carriers responsible for creating an electric current in semiconducting materials. These positively charged <strong>holes can move<\/strong> from atom to atom in semiconducting materials as electrons leave their positions. Adding trivalent impurities such as <strong>boron<\/strong>, <strong>aluminum,<\/strong> or <strong>gallium<\/strong> to an intrinsic semiconductor creates these positive electron holes in the structure. For example, a silicon crystal doped with boron (group III) creates a p-type semiconductor, whereas a crystal doped with phosphorus (group V) results in an n-type semiconductor.<\/p>\n<p>The number of acceptor sites completely dominates the number of electron holes. Therefore:<\/p>\n<p><strong>The total number of holes is approximately equal to the number of donor sites, p \u2248 N<\/strong><strong><sub>A<\/sub><\/strong><strong>. <\/strong><\/p>\n<p>The charge neutrality of this semiconductor material is also maintained. The net result is that the number of electron holes is increased while the number of conduction electrons is reduced. The imbalance of the carrier concentration in the respective bands is expressed by the different absolute number of electrons and holes. <strong>Electron holes<\/strong> are <strong>majority carriers<\/strong>, while electrons are minority carriers in p-type material.<\/p>\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>Acceptor Level<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Acceptor Level<\/strong><\/p>\n<p>From the <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/what-are-semiconductors-properties-of-semiconductors\/band-gap-energy-gap\/\">energy gap<\/a> viewpoint, such impurities \u201ccreate\u201d energy levels within the band gap <strong>close to the valence band<\/strong> so that electrons can be easily excited from the valence band into these levels, leaving mobile holes in the valence band. They create \u201cshallow\u201d levels, levels that are very close to the valence band, so the energy required to ionize the atom (accept the electron that fills the hole and creates another hole further from the substituted atom) is small. This shifts the effective Fermi level to a point about halfway between the acceptor levels and the valence band. Fermi level is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. The Fermi level is the surface of the Fermi sea at absolute zero, where no electrons will have enough energy to rise above the surface. In pure semiconductors, the position of the Fermi level is within the band gap, approximately in the middle of the band gap.<\/p>\n<\/div><\/div>\n<h3>The P-N Junction &#8211; Reverse Biased Junction<\/h3>\n<p>The <strong>semiconductor detector<\/strong> operates much better as a radiation detector if an external voltage is applied across the junction in the <strong>reverse-biased direction<\/strong>. The depletion region will function as a radiation detector. Improvement can be achieved by using a reverse-bias voltage to the P-N junction to <strong>deplete the detector<\/strong> of free carriers, which is the principle of most semiconductor detectors. Reverse biasing a junction increases the thickness of the depletion region because the potential difference across the junction is enhanced. Germanium detectors have a <strong>p-i-n structure<\/strong> in which the intrinsic (i) region is sensitive to ionizing radiation, particularly X and gamma rays. Under reverse bias, an electric field extends across the intrinsic or depleted region. In this case, a negative voltage is applied to the p-side and positive to the second one. Holes in the p-region are attracted from the junction towards the p contact and similarly for electrons and the n contact. In proportion to the energy deposited in the detector by the incoming photon, this charge is converted into a voltage pulse by an integral charge-sensitive preamplifier.<\/p>\n<p>See also: Germanium Detectors, MIRION Technologies. &lt;available from: https:\/\/www.mirion.com\/products\/germanium-detectors&gt;.<\/p>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>References:<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Radiation Protection:<\/strong><\/p>\n<ol>\n<li>Knoll, Glenn F., Radiation Detection and Measurement 4th Edition, Wiley, 8\/2010. ISBN-13: 978-0470131480.<\/li>\n<li>Stabin, Michael G., Radiation Protection, and Dosimetry: An Introduction to Health Physics, Springer, 10\/2010. ISBN-13: 978-1441923912.<\/li>\n<li>Martin, James E., Physics for Radiation Protection 3rd Edition, Wiley-VCH, 4\/2013. ISBN-13: 978-3527411764.<\/li>\n<li>U.S.NRC, NUCLEAR REACTOR CONCEPTS<\/li>\n<li>U.S. Department of Energy, Instrumentation, and Control. DOE Fundamentals Handbook, Volume 2 of 2. June 1992.<\/li>\n<\/ol>\n<p><strong>Nuclear and Reactor Physics:<\/strong><\/p>\n<ol>\n<li>J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).<\/li>\n<li>J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.<\/li>\n<li>W. M. Stacey, Nuclear Reactor Physics, John Wiley &amp; Sons, 2001, ISBN: 0- 471-39127-1.<\/li>\n<li>Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317<\/li>\n<li>W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467<\/li>\n<li>G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965<\/li>\n<li>Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.<\/li>\n<li>U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.<\/li>\n<li>Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 978-2759800414.<\/li>\n<\/ol>\n<\/div><\/div><div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-dotted\" style=\"margin:15px 0;border-width:2px;border-color:#999999\"><\/div><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<h2>See above:<\/h2>\n<p>Semiconductor Detectors<a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/semiconductor-detectors\/\" class=\"su-button su-button-style-flat\" style=\"color:#606060;background-color:#ffffff;border-color:#cccccc;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px\" target=\"_self\"><span style=\"color:#606060;padding:7px 20px;font-size:16px;line-height:24px;border-color:#ffffff;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px;text-shadow:0px 0px 0px #000000;-moz-text-shadow:0px 0px 0px #000000;-webkit-text-shadow:0px 0px 0px #000000\"><i class=\"sui sui-link\" style=\"font-size:16px;color:#5d5d5d\"><\/i> <\/span><\/a><\/p><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":26407,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"generate_page_header":""},"_links":{"self":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26462"}],"collection":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/comments?post=26462"}],"version-history":[{"count":3,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26462\/revisions"}],"predecessor-version":[{"id":38270,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26462\/revisions\/38270"}],"up":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26407"}],"wp:attachment":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/media?parent=26462"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}