Electronic Devices and Circuits

Q1: An n type semiconductor is illuminated by a steady flux of photons with energy greater than the band gap energy. The change in conductivity Δσ obeys which relation?
[ Here, e is the electron charge, μ_n electron mobility, μ_p hole mobility, Δ_n (Δ_p) is the excess electron (hole) density ].

A Δσ = 0

B Δσ = e(σ_n + σ_p) Δ_n

C Δσ = e(μ_nΔ_n - μ_pΔ_p)

D Δσ = e μ_nΔ_n

ANS:B - Δσ = e(σ_n + σ_p) Δ_n

Yeah its D. Since mobility and e are both constants so, if there will be a change in conductivity it is probably due to change in concentration of carriers.

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