Effect of the Near Surface Depletion Layer on Photo-Response of Direct Band Gap Semiconductor

Keneni Taye Serdo


In this study, the effects of the photo-responses of the near surface depletion layer and the deep bulk of gallium antimonide (GaSb) are investigated under different doping levels, injection level and illumination energies. First, the absorption rate of photons is described as a function of illumination energies at different locations inside the sample and as a function of the depth below the illuminated surface for photons with different energies. Then, the doping level dependence of the low injection level radiative, Auger and effective excess carrier lifetimes just under the surface and in the deep bulk are investigated by considering the variation of energy bending at the surface. The variation of the low injection level excess carrier lifetimes with the depth below the illuminated surface for samples with different doping levels is also described. This is followed by the description of the combined effects of doping and illumination energy on the photo-response of the entire bulk at slightly low injection level. Finally, the excess carrier injection level dependence of excess carrier lifetimes under the illuminated surface and deep bulk is also described for samples with different doping levels. Since photon absorption rate is directly related to the free carriers generation rate, the description of the photon absorption rate as functions of illumination energies and the depth below the illuminated surface is found to be the important and factors in the investigation in the photo-response of semiconductors along with the doping and the injection levels.  The analysis of the results also shows that, the under surface region is insensitive to the doping level and that of the deep bulk is highly affected by the doping level. The injection level dependence of the photo-response of the under surface region is similar for all samples with different doping. The energy of illumination each photon mainly suppresses the photo-responses of the points situated closer to the penetration depths of each photon below the illuminated surface of the sample.

Keywords: photo-response, direct band gap semiconductor, gallium antimonide GaSb

DOI: 10.7176/APTA/75-03


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ISSN (Paper)2224-719X ISSN (Online)2225-0638

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