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Basic Physics of Semiconductors(半导体的基本物理).pdf

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101 Basic Physics of Semiconductors * Einstein Relation: Our study of drift and diffusion has introduced a factor for each: (or ), and (or ), respectively. It can be proved that and are called the “Einstein Relation”: Note that: , at 300 K. Figure 1 summarizes the charge transport mechanisms. Fig.1 Summary of drift and diffusion mechanisms * PN Junction: We begin our study of semiconductor devices with the junction for three reasons. (1) The device finds application in many electronic systems, e.g., in adapters that charge the batteries of cell phones. (2) The pn junction is among the simplest semiconductor devices, thus providing a good entry point into the study of the operation of such complex structures as transistors. (3) The pn junction also serves as part of transistors. In this section, we study the properties and I/V characteristics of pn junctions. The following outline shows our thought process, indicating that our objective is to develop circuit models that pn junction see Fig. 2, the p and n sides are called the can be used in analysis and design. In a “ “anode” and the ”cathode” respectively. 101 102 Fig.2 Outline of concepts to be studied * PN Junction in Equilibrium Let us first study the pn junction with no external connections, i.e., the terminals are open and no voltage is applied across the device. We say the junction is in “equilibrium”. While seemingly of no practical value
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