Electroluminescence and photovoltaic effects of anodically fabricated metal/porous Si/Si sandwich structures based on n-type ultraviolet-porous Si


Unal B. , BAYLISS S.

JOURNAL OF APPLIED PHYSICS, cilt.80, ss.3532-3539, 1996 (SCI İndekslerine Giren Dergi)

  • Cilt numarası: 80 Konu: 6
  • Basım Tarihi: 1996
  • Doi Numarası: 10.1063/1.363226
  • Dergi Adı: JOURNAL OF APPLIED PHYSICS
  • Sayfa Sayısı: ss.3532-3539

Özet

The electroluminescence and photosensitive surface effects from metal/porous silicon/Si sandwich structures based on n-type ultraviolet-porous silicon were investigated in this study. Contacts were made by bonding to semitransparent coatings of Au (deposited by a novel technique of thermal evaporation) via Al electrodes. In the case of electroluminescence, studied by applying a current across the electrodes, orange light is emitted beneath the semitransparent gold film, and a reversible avalanche breakdown was observed at the interface at a reverse bias of around 22 V. The photosensitivity of the surface, which was coated with a thin gold film having an initial transmission of less than 60%, was observed to get worse when the above process was repeated several times, Furthermore, the avalanche breakdown voltage shifted slightly to higher values, possibly because of both structural fluctuations in the porous networks and/or Schottky conductive changes in between the metal-porous silicon interface resulting from the high current passed at breakdown and causing excess heat inside the device. Photovoltaic effects at the Schottky metal/porous Si barrier were also observed under a number of different types of illumination in the range from UV to visible, and under white light of different powers. The current-voltage characteristics of various sandwich structures operating as solar cells were measured, dong with the power efficiency of the solar cells under a calibrated tungsten bulb, this being over 0.35% under an illumination power of 12 mW/cm(2) The power efficiency (=-a+bP(in)) is found to increase linearly with increasing illumination power up to a saturation value that depends simply on preparation conditions. (C) 1996 American Institute of Physics.