新型电子第1章课件.pptVIP

CHAPER ONE SPECIAL DIODES 1.1 Introduction of this lesson 1.2 Introduction of semiconductor material 1. Conductors ◆ construction: have one, two or three valence electrons ◆ conductivity: materials that conduct electricity very easily ◆ examples: silver, copper, gold, and aluminum （have good conductors of electricity） 2. intrinsic semiconductor I. structure: a lattice structure the four valence electrons of each atom bond with the orbits of neighboring atoms to form a crystal structure called a lattice structure. II. temperature effect on resistance ◆ conductive materials: resistance increase with an increase in temperature ◆ semi conductive materials: resistance decrease with an increase in temperature Ⅲ. Why silicon is the most used semiconductor ◆ the ability to withstand heat ◆ intrinsic germanium exhibits about 1/1000th the amount of resistance as intrinsic silicon (2) extrinsic semiconductors N-type materials The structure of N-type materials (I) formation: doping semiconductor material with a pentavalent element such as arsenic, antimony or phosphorus. (II) majority current carriers: electrons (III) Conduction: caused by electron flow II. P-type materials struture of P-type material (I) formation: formed by doping semiconductor material with trivalent element such as aluminum, boron, gallium or indium. (II) majority current carriers: holes (III) Conduction: caused by hole flow III. PN-junction (I) formation: join N-type material and N-type material (II) barrier potential: a. formation : ◆ electrons and holes drifting ◆ positive ions are formed at the edge of the N -type material ◆ negative ions are formed at the edge of the P-type materials b. the voltage value of barrier potential: 0.3~0.4volts for germanium