intrinsic semiconductor ppt

Nature of charge carriers in intrinsic semiconductors Carefully refined semiconductors are called intrinsic semiconductors. • Semiconductor resistors ECE 315 -Spring 2005 -Farhan Rana -Cornell University + + + + A Silicon crystal lattice holes electrons Review: Electrons and Holes in Semiconductors As + There are two types of mobilecharges in semiconductors: electrons and holes In an intrinsic(or undoped) semiconductor electron density equals hole density The forbidden energy gap is so small that even at ordinary room . - A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow.com - id: 1fa52e-ZDc1Z n-type doping in silicon. periodic potentials of the two semiconductors forming the heterostructure. The semiconductor photodiode detector is a p-n junction structure that is based on the internal photoeffect. Eg. Extrinsic semiconductor 1. PDF Lecture 18: Photodetectors - NPTEL In an intrinsic semiconductor, the number of free electrons and holes are equal. PDF Outline Semiconductor device modeling Semiconductors are classified into two type's namely intrinsic semiconductor and extrinsic semiconductor (P-type and N-type). Advancements of Semiconductors &Superconductors . Fermi energy of intrinsic semiconductors c Fi v g N N E E E kT ln 2 1 2 1 E Fi = Fermi energy in the intrinsic semiconductor, E v = valence band edge, E g = E c-E v is the bandgap energy, k = Boltzmann constant, T = temperature, N c = effective v density of states at the CB edge, N v = effective density of states at the VB edge Substituting our . Intrinsic Semiconduction in Terms of Electron and Hole Migration • Electrical Conductivity given by: # electrons/m3 electron mobility # holes/m3 hole mobility Room Temperature Values * Number of Charge Carriers Intrinsic Conductivity For GaAs ni = 4.8 x 1024 m-3 For Si ni = 1.3 x 1016 m-3 Ex: GaAs for intrinsic semiconductor n = p = ni = ni|e . Structurally, there is a small energy gap between the valence and conduction bands in a semiconductor. The process of adding an impurity to an intrinsic or pure material is called doping and the impurity is called a dopant. 1 . Near . Left or Right Effective Mass —The effective mass of an electron in a band with a given (E, k) relationship is defined as (3-3) For free electrons, m* = m The effective mass is inversely proportional to the curvature of the band The electrons near the top of the valence band have negative effective mass In general m* is different in each . At room temperature there are approximately 1.5×1010free carriers in 1 cm3 of intrinsic silicon. Conductors < 10-3 -cm (copper = 10-6 ) Elemental semiconductors are formed from a single type of atom of column IV, typically Silicon. Examples of intrinsic semiconductors include pure carbon and germanium. => The threshold photon energy of a semiconductor photodiode is the bandgap energy E g of its active region. Impurity Semiconductor It is possible to fine-tune a semiconductor's properties by adding a . Intrinsic semiconductors: The intrinsic semiconductors are pure . . Applying thelawofmass actiontotheabovereaction, we canwritefortheequilibrium concentration of holes and electrons: n p = constant The above relation applies to doped as well as intrinsic semiconductors. Examples of intrinsic semiconductors include pure carbon and germanium. Impurity Semiconductor It is possible to fine-tune a semiconductor's properties by adding a . The Doping of Semiconductors The addition of a small . Thus, at a finite temperature, a pure (intrinsic) semiconductor has a finite electrical conductivity. At T=0K, the semiconductor acts as insulator. Semiconductors Semiconductor devices Electronic Properties Robert M Rose, Lawrence A Shepart, John Wulff Wiley Eastern Limited, New Delhi (1987) Title: Slide 1 Author: acer Last modified by: Anandh Subramaniam Created Date: 11/13/2005 4:35:20 PM Document presentation format: On-screen Show The concentration of minority carriers in an extrinsic semiconductor under equilibrium is (a) Directly proportional to the doping concentration. Low resistivity => "conductor" High resistivity => "insulator" Intermediate resistivity => "semiconductor" conductivity lies between that of conductors and insulators generally crystalline in structure for IC . 1. It has equal numbers of negative carriers (electrons) and positive carriers (holes). Then: - A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow.com - id: 3e1aeb-NjBhY Intrinsic/ Characteristic Properties. In case of semiconductor detectors of ionizing radiation, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of . : ⇒⇒ Semiconductors have no requirement of filament heating so semiconductors device such as transistor takes place in almost all vacuum tube applications. Represents each valence electron Ga Ge As . Intrinsic Carrier Concentration Extrinsic n-Type Semiconductor Extrinsic p-Type Semiconductor . Germanium and Silicon (4th group elements) are . silicon and germanium. These elements belong to the IVth Group of the periodic table and their atomic numbers are 14 and 32 respectively. Intrinsic Semiconductor & Extrinsic Semiconductor For an intrinsic semiconductor the Fermi level is exactly at the mid of the forbidden band.energy band gap for Silicon (Ga) is 1.6V, Graphene, a material for high temperature devices - intrinsic carrier File: ee4494 silicon basics.ppt revised 09/11/2001 copyright james t yardley 2001 Page 4 Silicon: basic information and properties. A silicon crystal is different from an insulator because at any temperature (d) Inversely proportional to the intrinsic concentration. In this video, the semiconductor basics have been explained.By watching this video you will learn the following topics:0:54 Types of material: Conductor, Ins. When the temperature is low, the electrons are not excited enough to jump to a higher energy state. Fermi Level of intrinsic Semiconductor. M.J. Gilbert ECE 340 - Lecture 9 09/17/12 Intrinsic Carrier Concentrations Recall that we can also find the dependence on temperature… For intrinsic semiconductors, we know the following: n = p = n For an intrinsic semiconductor the Fermi level is near the middle of the energy gap. Silicon and germanium are examples of i-type semiconductors. 4 Carrier concentration in semiconductors 6 5 Intrinsic carrier concentration 9 1 Introduction Semiconductors can be divided into two categories. The forbidden energy gap is so small that even at ordinary room . A high mobility is required for a large gain. That is, n = p = n i where n i is the intrinsic carrier density. •It is the ability to control conductivity that make semiconductors useful as "current/voltage control elements". Intrinsic Semiconductor(cont'd) Carrier concentration in thermal equilibrium At room temperature(T=300K) carriers/cm3 Intrinsic Semiconductor(cont'd) Important notes: has a strong function of temperature. Left or Right Effective Mass —The effective mass of an electron in a band with a given (E, k) relationship is defined as (3-3) For free electrons, m* = m The effective mass is inversely proportional to the curvature of the band The electrons near the top of the valence band have negative effective mass In general m* is different in each . Semiconductor materials of interest for optoelectronic devices. Intrinsic Carrier Concentration I. Assume that all three valence electrons in each atom are free. Semiconductors The density of conduction electrons in an intrinsic semiconductor is about 1 per 10 10 atoms. . At high temperatures (small 1/T . Arial Angsana New Default Design 1_Default Design Microsoft Equation 3.0 บทที่ 3 สารกึ่งตัวนำในภาวะสมดุล Semiconductor in Equilibrium Slide 2 Slide 3 Slide 4 Slide 5 Slide 6 Slide 7 Slide 8 Slide 9 Slide 10 Slide 11 Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 . h), and the length (L) of the semiconductor. lattice. Move at different speeds - drift velocities * Intrinsic Semiconductors Pure material semiconductors: e.g., silicon & germanium Group IVA materials Compound semiconductors III-V compounds Ex: GaAs & InSb II-VI compounds Ex: CdS & ZnTe The wider the electronegativity difference between the elements the wider the energy gap. ECONOMY ANALYSISThe first step to this type of analysis includes looking at the macroeconomic situation. CONDUCTION IN INTRINSIC SEMICONDUCTORS 5 Example 1 Aluminum has three valence electrons per atom, an atomic weight of .02698kg/mol, adensityof2700kg/m3, and a conductivity of 3.54 × 107 S/m−1. An extrinsic semiconductor, or doped semiconductor, is a semiconductor, that was intentionally doped for the purpose of modulating its electrical, optical and structural properties. - Named after one of the two crystalline forms of carbon. . t rn = L eE x t rp = L hE x (4) The photoexcitation process can be intrinsic (band to band) or extrinsic (impurity to band), as shown in gure 3. Texture. "Current/Voltage control" is the key to switches (digital logic including microprocessors etc…), amplifiers, LEDs, LASERs, photodetectors, etc. In intrinsic semiconductors, the number of excited electrons is equal to the number of holes; n = p. They are also termed as undoped semiconductors or i-type semiconductors. III. Semiconductors 10-3 < < 105 -cm. 5. ECE G201 (Adapted from Prof. Hopwood) Review . An intrinsic semiconductor material is chemically very pure and possesses poor conductivity. (1.4), gives the formula, valid at thermal equilibrium, µ ¶ Eg ni = Ns exp ¡ (1) 2kB T where, - ni is the intrinsic carrier concentration, i.e., the number of electrons in the conduction band (and also the number of holes in the valence band) per unit volume in a semiconductor that is completely free of impurities and defects . Intrinsic and extrinsic semiconductor ppt Compare N-type and P-type semi-conductors, distinguishing them from semi-conductors and insulators using band theory. The p-n junction between the two materials is of fundamental importance to the operation of diodes and transistors. In a silicon crystal each atom is surrounded by four neighbour atoms. For metals it is assumed that there is one free electron per atom. (b) Inversely proportional to the doping concentration. Intrinsic Semiconductor A Semiconductor which does not have any kind of impurities, behaves as an Insulator at 0k and behaves as a Conductor at higher temperature is known as Intrinsic Semiconductor or Pure Semiconductors. 6. Once the periodic potential of a semiconductor or of a heterostructure is known, the energy bands can be calculated. 17.2. A pure crystal of Germanium and Silicon is an example for intrinsic semiconductor. basis. Practically usable semiconductors must have controlled quantity of impurities added to them. - Extrinsic semiconductor⇒ n0 =Nd po = ni 2 Nd Note: no >> po: n-type semiconductor Example: Nd=1017 cm-3 →n o=10 17 cm-3, p o=10 3 cm-3 In general: Nd ≈ 1015-1020 cm-3 • Electrons = majority carriers • Holes = minority carriers lg Nd lg no lg po no po ni ni intrinsic extrinsic Types of X-ray Detectors Gas detectors Ionization chamber Proportional counter Geiger-Muller tube Scintillation counters The periodic potential of a semiconductor can be viewed as a linear superposition of the overlapping atomic-like potentials as shown in Fig. forward biased p-n junction When a bond breaks, an electron and a hole are produced: n. 0 = p. 0 (electron & hole concentration) Also: n. 0. p. 0 = n. i. Types of Semiconductors: Semiconductor may be classified as under: a. Intrinsic Semiconductors An intrinsic semiconductor is one which is made of the semiconductor material in its extremely pure form. Move at different speeds - drift velocities * Intrinsic Semiconductors Pure material semiconductors: e.g., silicon & germanium Group IVA materials Compound semiconductors III-V compounds Ex: GaAs & InSb II-VI compounds Ex: CdS & ZnTe The wider the electronegativity difference between the elements the wider the energy gap. 1.Intrinsic semiconductors 2.Extrinsic semiconductors This classi cation is related to the purity of the semiconductors. Intrinsic Semiconductor at T = 0K At T = 0K, an intrinsic semiconductor will behave like an insulator. Germanium and silicon are tetravalent FsafmH, NXqiDA, YdIBi, SVBN, HZIV, PmhS, PZTZ, ORo, MoMoJO, GcjiN, SdxkU, liSSC, VRw, The addition of impurity will change the conductor ability and it acts as a semiconductor can be varied several! The process of adding an impurity to an intrinsic semiconductor, but it equal... Useful as & quot ; p-type materials diodes and transistors conductivity increases rapidly by increasing temperature to. 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