Assuming that the electron mobility in intrinsic silicon

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Assuming that the electron mobility in intrinsic silicon is 1500 cm²/Vs room temperature (T = 300K) and the corresponding ‘volt equivalent of temperature’ V_T = 25·9 mV, what is the approximate value of the electron diffusion constant?

1. 40 cm²/s
2. 4 cm²/s
3. 400 cm²/s
4. 4000 cm²/s

Correct Option: A

Given, µ_n = 1500 cm²/V-sec
V_T = 25·9 mV
D_n =?

We know that	D_n	= VT
	µ_n

where,
D_n = Diffusion constant
µ_n = Mobility of electron
V_T = Volt equivalent of temperature
Now, D_n = µ_n V_T = 1500 × 25·9 × 10^–3 cm²/s = 38·85 cm²/s or D_n 40 cm²/s
Hence alternative (A) is the correct choice.