There could be three forms of velocity a carrier can have experience within a semiconductor lattice.Consider following questions associated to the carrier velocity. (a) What is the difference between the thermal velocity, drift velocity and velocity due to diffusion?Describe by describing the origin of each of these. (b) Which of the above can contribute to current in a semiconductor material. (c) Describe equations associated to each of the above. Write the relation for velocity for each case. (d) What is the origin of mobility u and diffusion constant D. Write the equation that relates them,what is this relation called?

Fig: 1

Fig: 2

Fig: 3

Fig: 4

Fig: 5