Electron mobility (solid-state physics) | Wikipedia audio article
Channel: wikipedia tts
Date: 2019-05-04

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Electron_mobility


00:02:48 1 Introduction
00:02:57 1.1 Drift velocity in an electric field
00:04:31 1.2 Definition and units
00:05:58 1.3 Relation to conductivity
00:06:38 2 Examples
00:08:58 3 Electric field dependence and velocity saturation
00:09:58 4 Relation between scattering and mobility
00:13:37 4.1 Ionized impurity scattering
00:15:17 4.2 Lattice (phonon) scattering
00:17:10 4.3 Piezoelectric scattering
00:17:47 4.4 Surface roughness scattering
00:18:28 4.5 Alloy scattering
00:19:11 4.6 Inelastic scattering
00:20:04 4.7 Electron–electron scattering
00:21:02 4.8 Relation between mobility and scattering time
00:21:46 4.9 Matthiessen's rule
00:22:55 4.10 Temperature dependence of mobility
00:28:26 5 Measurement of semiconductor mobility
00:33:02 5.1 Hall mobility
00:33:12 5.2 Field-effect mobility
00:42:01 5.2.1 Using saturation mode
00:42:39 5.2.2 Using the linear region
00:44:44 5.3 Optical mobility
00:47:03 5.4 Terahertz mobility
00:47:37 6 Doping concentration dependence in heavily-doped silicon
00:48:05 7 See also
00:53:02 8 References



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SUMMARY
=======
In solid-state physics, the electron mobility characterises how quickly an electron can move through a metal or semiconductor, when pulled by an electric field. There is an analogous quantity for holes, called hole mobility. The term carrier mobility refers in general to both electron and hole mobility.
Electron and hole mobility are special cases of electrical mobility of charged particles in a fluid under an applied electric field.
When an electric field E is applied across a piece of material, the electrons respond by moving with an average velocity called the drift velocity, 
  
    
      
        
        
          v
          
            d
          
        
      
    
    {\displaystyle \,v_{d}}
  . Then the electron mobility μ is defined as

  
    
      
        
        
          v
          
            d
          
        
        =
        μ
        E
      
    
    {\displaystyle \,v_{d}=\mu E}
  .Electron mobility is almost always specified in units of cm2/(V·s). This is different from the SI unit of mobility, m2/(V·s). They are related by 1m2/(V·s) = 104cm2/(V·s).
Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small number of electrons with high mobility for each, or a large number of electrons with a small mobility for each. For metals, it would not typically matter which of these is the case, since most metal electrical behavior depends on conductivity alone. Therefore mobility is relatively unimportant in metal physics. On the other hand, for semiconductors, the behavior of transistors and other devices can be very different depending on whether there are many electrons with low mobility or few electrons with high mobility. Therefore mobility is a very important parameter for semiconductor materials. Almost always, higher mobility leads to better device performance, with other things equal.
Semiconductor mobility depends on the impurity concentrations (including donor and acceptor concentrations), defect concentration, temperature, and electron and hole concentrations. It also depends on the electric field, particularly at high fields when velocity saturation occurs. It can be determined by the Hall effect, or inferred from transistor behavior.