Similar questions

Explain the following terms:

i. Quantum efficiency

ii. Responsivity

Marks: 2M/5M

Year: Dec2014, Dec2013, May2013, May2012,May2014

Quantum Efficiency ɳ:

1.Quantum Efficiency is defined as the ratio of number of electrons collected to the number of incident photons.

1. It is also defined as ratio of generated current flux to input photon flux.

$ɳ_q = \frac{number \ \ ofelectrons \ \ collected}{number \ \ ofincident \ \ photons}$

$ɳ_q = \frac{R_e}{R_p}$ = Quantum efficiency

Responsivity:

1. It represents the sensitivity of a photodetector.

2. The function of photodetector is to convert the optical signal into electrical signal.

3. More photons that strike the photodetector, more change carriers will be produced. i.e greater will be the photo current I.

4. The performance of a photodiode is characterized by a term Responsivity R.

5. Photocurrent is directly proportional to incident optical power ($P_{in}$).

$$I_p α P_{in} \\ \; \\ I_p = RP_{in}$$

As the energy of photon E = hv, then incident photon rate $R_p = \frac{P_{in}}{hv}$

where

$P_{in}$ = incident optical power

Electron rate $R_e = \frac{I_p}q$

Quantum efficiency $ɳ = \frac{R_e}{R_p}$

$$\boxed{R = \frac{ɳqλ}{hc}}$$

where v = c/λ and hc = E_p(energy of photon)

From above equation, Responsivity is directly proportional to Quantum efficiency at particular wavelength.