Many engineers are having misconception on the relationship between temperature and electron mobility.
Well, if you awake only during the first 15 minutes of semiconductor fundamental lecture, then you may think that high temperature results in higher electron mobility. The answer is it depends. It is just one piece of story.
In the first place, high temperature will help electron to excite from valence to conduction band as mentioned in my earlier post. This is related to ion impurity. As the temperature gets increased further, the lattice (phonon) start to move. As more and more electrons get excited, there is a congestion of them leading to higher probability of collisions. This slows down the mobility. The higher the doping concentration, the slower the electron mobility.
As shown in the chart on the left, the higher the doping concentration results in higher probability of collisions. This causes the electron mobility to drop.
Then, at what temperature does the higher electron mobility be at? You may for a while think that it must have been at lower temperature. But that is not true.
As the figure on the right shows, there is an optimum temperature whereby it yields in higher electron mobility.
The figure illustrates clearly what I have mentioned above. There are two types of phenomena affecting the electron mobility. First being the impurity scattering and second being the lattice scattering.
The optimum temperature also depends on the doping concentration. As you see on the 5 curve lines illustrating different doping concentration. At 10^19, the optimum temperature is higher than the one for 10^18 and so on. Clearly at 10^14, the curve line is not yet shown sign of going down at ~150K.
Well hope this helps to clear your doubts. Nothing heavy, but good enough to get us to a proper foot-ground.
Cheers,
Pungky
Well, if you awake only during the first 15 minutes of semiconductor fundamental lecture, then you may think that high temperature results in higher electron mobility. The answer is it depends. It is just one piece of story.
In the first place, high temperature will help electron to excite from valence to conduction band as mentioned in my earlier post. This is related to ion impurity. As the temperature gets increased further, the lattice (phonon) start to move. As more and more electrons get excited, there is a congestion of them leading to higher probability of collisions. This slows down the mobility. The higher the doping concentration, the slower the electron mobility.
Then, at what temperature does the higher electron mobility be at? You may for a while think that it must have been at lower temperature. But that is not true.
The figure illustrates clearly what I have mentioned above. There are two types of phenomena affecting the electron mobility. First being the impurity scattering and second being the lattice scattering.
The optimum temperature also depends on the doping concentration. As you see on the 5 curve lines illustrating different doping concentration. At 10^19, the optimum temperature is higher than the one for 10^18 and so on. Clearly at 10^14, the curve line is not yet shown sign of going down at ~150K.
Well hope this helps to clear your doubts. Nothing heavy, but good enough to get us to a proper foot-ground.
Cheers,
Pungky
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