Electron mobility and life-time in a semiconductor at room

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Electron mobility and life-time in a semiconductor at room temperature are respectively 0.36m²/(Vs) and 340 µs. The diffusion length is:

1. 3.13 mm
2. 1.77 mm
3. 3.55 mm
4. 3.13 cm

Correct Option: B

We know that
L_n = √ D_nt_n
or L_n = √ µ_nV_Tt_n
where, L_n = Diffusion length
D_n = Diffusion constant
µ_n = Mobility of electron
t_n = Life-time of electron
V_T = Volt equivalent temperature = 26 mV
Given, µ_n = 0·36 m²/V.sec
t_n = 340 µs = 340 × 10–6 sec.
Now, L_n = √ 0.36 × 26 × 10^–3 × 340 × 10^–6
or L_n ≈ 1.77 mm