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一、前言根据物质导电的能力,可以把它們分为三类:即导体(金属)、半导体和絕缘体。三类物质的能带分布如图1所示。从图1可以看出金属与絕緣体和半导体不同,在价电子带(滿带)与导带之間沒有禁带(△E=0),因此价电子都可以参与电流的传导作用。半导体的能谱中則有禁带存在,因此在正常状态下处于滿带中的价电子不能参与电流的传导作用。但是当受到热激活或光激活作用时,滿带中的电子可以被激发至导带,因而具有一定的电导。绝缘体在这方面与半导体并无原则区别,只是禁带宽度較大,换句话说,也就是把电子激发至导带时所需的激活能較大。此外,金属的电导随温度的升高而降低,而半导体的电导則随溫度的升
I. INTRODUCTION According to the material conductive ability, they can be divided into three categories: the conductor (metal), semiconductors and insulators. Three types of material with the band distribution shown in Figure 1. It can be seen from Figure 1 that metal is different from insulator and semiconductor in that there is no band gap between the valence band (full band) and the conduction band (ΔE = 0), so the valence electrons can participate in the current conduction. There are band gaps in the semiconductor’s energy spectrum, so the valence electrons in the full band under normal conditions can not participate in the current conduction. But when subjected to thermal or photo-activation, the electrons in the full band can be excited to the conduction band and thus have a certain conductance. Insulators in this regard and the semiconductor there is no principle difference, except for a larger band gap, in other words, that is, the activation of electrons to the conduction band when the activation energy required. In addition, the conductance of metals decreases with increasing temperature, while the conductivity of semiconductors increases with temperature