Lec3

Lec3 - Subject_03 Outline Introductory Concepts...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Introductory Concepts * Semiconductors Materials properties * Semiconductor energy bands Energy bands and forbidden gap Subject_03: Outline
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A proper understanding of the properties of semiconductor devices requires a detailed knowledge of the corresponding semiconductor MATERIALS from which they are fabricated * A semiconductor may be considered as a material whose electrical conductivity is INTERMEDIATE between that of a METAL and an INSULATOR * A NUMBER of different semiconductors are encountered in nature and these may be classified as either ELEMENTAL or COMPOUND semiconductors II III IV V VI Be Mg Zn Cd Hg B Al Ga In Tl Si Sn Ge C Pb Bi Sb As P N O S Se Te Po ELEMENTAL SEMICONDUCTORS ARE INDICATED IN BOLD Semiconductors Plot Energy Band Diagrams for: semiconductor/insulator/metal
Background image of page 2
The vast majority of semiconductors are COMPOUND semiconductors which may in turn be classified into a number of different groupings COMPOUND TYPE IV-IV III-V II-VI IV-VI Alloys * SEMICONDUCTOR SYMBOL SiC AlP AlAs GaN GaP GaAs ZnSe ZnTe CdSe CdTe PbSe PbTe Si 1-x Ge x Al x Ga 1-x As Al x In 1-x As SEMICONDUCTOR NAME Silicon Carbide Aluminum Phosphide Aluminum Arsenide Gallium Nitride Gallium Phosphide Gallium Arsenide Zinc Selenide Zinc Telluride Cadmium Selenide Cadmium Telluride Lead Selenide Lead Telluride Silicon Germanium Aluminum Gallium Arsenide Aluminum Indium Arsenide NOTE THAT THIS TABLE CONTAINS JUST A FEW LIMITED EXAMPLES OF COMPOUND SEMICONDUCTORS * ALLOYS ARE USUALLY DEFINED AS “A METALLIC MIXTURE OF METALS AND NON METALS” BUT THIS NEED NOT ALWAYS BE THE CASE Semiconductors
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The great advantage of semiconductor materials is that it is possible to VARY their conductivity over a much WIDER range than is possible in either metals or insulators * This is achieved by the CONTROLLED addition of a SMALL number of impurities known as DOPANTS * The number of dopants that is added to the semiconductor is typically a VERY SMALL fraction of the total number of atoms in the semiconductor Dopant levels normally range from one dopant atom per 10 8 to one dopant per 10 3 atoms of semiconductor atom A SCHEMATIC DIAGRAM THAT ILLUSTRATES THE DOPING CONCEPT THE SEMICONDUCTOR THAT IS TO BE DOPED IS PLACED INSIDE A SUITABLE HIGH-TEMPERATURE FURNACE AND THE DOPING ELEMENT IS THEN ADMITTED TO THE FURNACE IN GASEOUS FORM DOPANT ATOMS ARE INCORPORATED INTO THE SEMICONDUCTOR AND DIFFUSE DOWNWARDS BELOW ITS SURFACE THE DEPTH OF DIFFUSION IS SENSITIVE TO THE FURNACE TEMPERATURE AND DOPANT PRESSURE AND MAY BE CALIBRATED TO HIGH PRECISION AN ELEMENTARY BUT INTERESTING TUTORIAL ON THE FABRICATION OF INTEGRATED CIRCUITS CAN BE FOUND AT THE INTEL WEB SITE DOPANT ATOMS DOPED REGION UNDOPED SUBSTRATE Semiconductors
Background image of page 4
Semiconductors are generally inorganic solid materials that may occur in AMORPHOUS , POLYCRYSTALLINE or CRYSTALLINE forms * In the AMORPHOUS state there is little or NO
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/28/2011 for the course EE 2 taught by Professor Vis during the Winter '07 term at UCLA.

Page1 / 24

Lec3 - Subject_03 Outline Introductory Concepts...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online