Problem $5\mathrm{.}4$

a$)$ A silicon P$-$I$-$N photodiode has an active light$-$receiving area of diameter $0\mathrm{.}4$ mm$.$ When light of

wavelength $700$ nm and an intensity of $0\mathrm{.}1$ mW$/$cm$2$ is incident on the diode, it generates a

photocurrent of $56\mathrm{.}6$nA$.$ What is the responsivity and external quantum efficiency of the

photodiode at $700$ nm $?$

b$)$ An InGaAs avalanche photodiode has a quantum efficiency, $,$ of $60\%$ at $1\mathrm{.}55$m in the absence

of multiplication $(=1).$ It is biased to operate with a multiplication factor of $12.$ Calculated the

photocurrent if the incident optical power is $20$nW$.$ What is the responsivity when the

multiplication factor is $12?$