Optical response of In_xGa_1-xAs pin detector

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SUMMARY

The discussion focuses on the optical response of a GaAs/InGaAs/Si top-illuminated pin photodetector, specifically analyzing the photocurrent versus wavelength for varying compositions of In_xGa_1-xAs. The doping concentrations are set at 1e17 for p-type GaAs, 1e14 for the i-layer In_xGa_1-xAs, and 1e18 for n-type Si. The expected peak wavelengths for compositions x=0.05 and x=0.1 are 0.918 micrometres and 0.970 micrometres, respectively, based on their bandgap energies of 1.351 eV and 1.279 eV. However, for x=0.2 and x=0.3, the expected peaks disappear, indicating a need for further investigation into the physical mechanisms at play.

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  • Understanding of semiconductor physics, particularly bandgap energy and its relation to photocurrent.
  • Familiarity with the properties of InGaAs and its applications in photodetectors.
  • Knowledge of doping concentrations and their effects on semiconductor behavior.
  • Experience with optical characterization techniques for photodetectors.
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  • Research the effects of varying doping concentrations on the performance of InGaAs photodetectors.
  • Study the relationship between bandgap energy and wavelength in semiconductor materials.
  • Explore the physical mechanisms causing the disappearance of photocurrent peaks in In_xGa_1-xAs layers.
  • Investigate advanced optical characterization methods for analyzing photodetector responses.
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Researchers, optical engineers, and semiconductor physicists interested in the design and optimization of photodetectors, particularly those working with InGaAs materials.

ribella
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TL;DR
Plot of the photocurrent versus the wavelength of light of a GaAs/InGaAs/Si top-illuminated pin photodetector
Greetings,

I am trying to obtain a plot of the photocurrent versus the wavelength of light of a GaAs/InGaAs/Si top-illuminated pin photodetector, where the doping ratio for p-type GaAs is conc=1e17, for i-layer In_xGa_1-xAs conc=1e14 and for n-type Si conc=1e18. Firstly, for x=0.05, if we illuminate this structure with top light, the plot of the photocurrent versus the wavelength of light we obtain is as follows:
1726818041237.png


For x=0.1:

1726818141092.png


For x=0.2:

1726818158378.png


Finally, for x=0.3:

1726818194029.png


What I don't fully understand here is that the In_xGa_1-xAs layer is the active layer here and Eg=1.351 eV for x=0.05, so I would expect a peak of around 0.918 micrometres in the wavelength plot of the current coming out of the pin detector. The same situation is Eg=1.279 eV for x=0.1 and the corresponding cut-off wavelength is a peak at 0.970 micrometres. Moreover, for x=0.2 and 0.3 the peak disappears as you can see in the graphs. What could be the physical explanation for these phenomena?
 

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