A p-type Si sample is used in the Haynes-Shockley experiment. The length of the sample is 2 cm, and two probes are separated by 1.8 cm. Voltage applied at the two ends is 5 V. A pulse arrives at the collection point at 0.608 ms, and the separation of the pulse is 180 sec. Calculate mobility and diffusion coefficient for minority carriers. Verify it from the Einstein relation.

Mobility of the minority carriers,

Diffusion coefficient for minority carriers,

Verified from Einstein relation as  

Explanation:

Length of sample,

Separation between the two probes, L = 1.8 cm

Drift time,

Applied voltage, V = 5 V

Mobility of the minority carriers ( electrons),

Where the drift velocity,

and the Electric field strength,

E = 5/2

E = 2.5 V/cm

Mobility of the minority carriers:

The electron diffusion coefficient,

, where Δt = separation of pulse seen in an oscilloscope in time( it should be in micro second range)

For the Einstein equation to be satisfied,

Verified.

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