Optoelectronics problem. Please assist

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In summary, the given problem involves a phosphorus-doped Si photoconductor exposed to far IR radiation. The steady state resistance is 550 Ω and takes 20 μs to rise to 1 kΩ after the radiation is switched off. Using the dimensions of the photoconductor, the wavelength of IR, and the electron and hole mobility, the intensity of the far IR radiation and the carrier lifetime can be calculated. To find the intensity, it can be assumed that each excited carrier corresponds to a passing photon, and the photon energy and radiant power per unit area can be estimated. The photoconductor's conductivity changes with the absorbed photons, and the i-v curve is linear in the dark. Under voltage bias, the
  • #1

Homework Statement

A phosphorus (P) doped Si photoconductor is exposed to far IR radiation of unknown intensity. Its
steady state resistance is found to be 550 Ω. The far IR radiation is then
switched off, and the resistance of the photoconductor takes 20 μs to rise to 1
kΩ. Calculate the
i) intensity of the far IR radiation,
ii) carrier lifetime

Homework Equations

Dimensions of photoconductor = (Lx × Ly × Lz) = 6 mm × 25 mm × 12 mm
(N.B. current is flowing in the x-direction, while the far IR radiation is incident
on the x-y plane of the photoconductor).
Wavelength of IR, λ = 12 μm
Electron mobility μ
e = 2500 cm2 V−1 s−1
Hole mobility μh = 1800 cm2 V−1 s−1

The Attempt at a Solution

My attempt
Since the photoconductor was doped with P, the electron would be the majority carrier. And i equate
I = Area * (eVn + eVp)
= Area * (eVn)
And from this i would get

R= (length/area) 1/(eμn)
Since i have the resistance for steady state and during no illumination
I can apply the above formula with the resistance to find the n created by photons and the intrinsic n.

After which i have no idea what so ever on how to look for the intensity. Please help
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  • #2
Perhaps you could assume that every excited carrier corresponds to a photon passing through the sample. You should be able to estimate the photon energy quite precisely. Then calculate the radiant power per unit area incident on the sample.
  • #3
thanks.. will definitely try that out. Another question that came to my mind is a photoconductor's conductivity changes according to the absorbed incident photons. So the i-v curve would be linear? in the dark? And what happens under voltage bias? I keep thinking of a diode's i-v curve.

Related to Optoelectronics problem. Please assist

1. What is optoelectronics?

Optoelectronics is the branch of technology that deals with the study and application of electronic devices that can emit, detect, and control light.

2. What are some common optoelectronics problems?

Some common optoelectronics problems include device malfunction, signal interference, and difficulty in achieving desired performance levels.

3. How are optoelectronics problems solved?

Optoelectronics problems are often solved by troubleshooting and identifying the root cause of the issue. This may involve testing and replacing faulty components, adjusting settings, or redesigning the device.

4. What are some applications of optoelectronics?

Optoelectronics has a wide range of applications, including in fiber optic communication, medical imaging, solar energy, and consumer electronics such as LED displays and laser printers.

5. What skills are required to solve optoelectronics problems?

Solving optoelectronics problems requires a strong understanding of electronics, optics, and materials science. It also requires critical thinking and problem-solving skills, as well as the ability to analyze data and troubleshoot technical issues.

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