1 / 8

Intrinsic vs Extrinsic Conduction

Intrinsic vs Extrinsic Conduction. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. • n -type Extrinsic: ( n >> p ). • p -type Extrinsic: ( p >> n ). 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +. 4. +.

ava-herman
Download Presentation

Intrinsic vs Extrinsic Conduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Intrinsic vs Extrinsic Conduction 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + • n-type Extrinsic: (n >> p) • p-type Extrinsic: (p >> n) 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + Phosphorus atom Boron atom hole conduction electron 5+ 3 + valence electron no applied no applied Si atom Adapted from Figs. 18.12(a) & 18.14(a), Callister & Rethwisch 8e. electric field electric field • Intrinsic: -- case for pure Si -- # electrons = # holes (n = p) • Extrinsic: -- electrical behavior is determined by presence of impurities that introduce excess electrons or holes -- n ≠ p

  2. doped undoped 3 2 freeze-out extrinsic intrinsic concentration (1021/m3) Conduction electron 1 0 0 200 400 600 T (K) Adapted from Fig. 18.17, Callister & Rethwisch 8e. (Fig. 18.17 from S.M. Sze, Semiconductor Devices, Physics, and Technology, Bell Telephone Laboratories, Inc., 1985.) Extrinsic Semiconductors: Conductivity vs. Temperature • Data for Doped Silicon: -- s increases doping -- reason: imperfection sites lower the activation energy to produce mobile electrons. • Comparison:intrinsic vs extrinsic conduction... -- extrinsic doping level: 1021/m3 of a n-type donor impurity (such as P). -- for T < 100 K: "freeze-out“, thermal energy insufficient to excite electrons. -- for 150 K < T < 450 K: "extrinsic" -- for T >> 450 K: "intrinsic"

  3. Hall Effect 18.41 A hypothetical metal is known to have an electrical resistivity of 4  10-8 (W-m). Through a specimen of this metal that is 25 mm thick is passed a current of 30 A; when a magnetic field of 0.75 tesla is simultaneously imposed in a direction perpendicular to that of the current, a Hall voltage of -1.26  10-7 V is measured. Compute (a) the electron mobility for this metal, and (b) the number of free electrons per cubic meter.

  4. p-n Rectifying Junction + - + - + + - - + - p-type - n-type + + + - + - - + - - + n-type - p-type + + - - + + - + - + - • Allows flow of electrons in one direction only (e.g., useful to convert alternating current to direct current). • Processing: diffuse P into one side of a B-doped crystal. p-type n-type -- No applied potential: no net current flow. Adapted from Fig. 18.21 Callister & Rethwisch 8e. -- Forward bias: carriers flow through p-type and n-type regions; holes and electrons recombine at p-n junction; current flows. -- Reverse bias: carriers flow away from p-n junction; junction region depleted of carriers; little current flow.

  5. Properties of Rectifying Junction Fig. 18.22, Callister & Rethwisch 8e. Fig. 18.23, Callister & Rethwisch 8e.

  6. Junction Transistor Fig. 18.24, Callister & Rethwisch 8e.

  7. MOSFET Transistor Integrated Circuit Device • Integrated circuits - state of the art ca. 50 nm line width • ~ 1,000,000,000 components on chip • chips formed one layer at a time Fig. 18.26, Callister & Rethwisch 8e. • MOSFET (metal oxide semiconductor field effect transistor)

  8. Capacitance 18.51 Consider a parallel-plate capacitor having an area of 2500 mm2 and a plate separation of 2 mm, and with a material of dielectric constant 4.0 positioned between the plates. (a) What is the capacitance of this capacitor? (b) Compute the electric field that must be applied for 8.0  10-9 C to be stored on each plate.

More Related