engleski

Silicon/organic thin film heterojunctions for optoelectronic devices

Although silicon CMOS has been the process of choice for many uses in optoelectronic industry, its use for IR sensitive optoelectronic devices is limited to below ~1100 nm by the 1.11 eV band-gap of silicon. Extending the optical sensitivity range of silicon devices up to several microns, while maintaining good sensor responsivity, short rise and fall times, and maintaining the CMOS process compatibility, would be of great importance for possible telecom or other optoelectronic uses. Heterojunction interfaces between organic thin films and silicon often show synergetic advantages regarding certain properties. We present our work on optoelectronic devices based on heterojunctions of silicon and organic thin films of hydrogen- bonded pigment tyrian purple (6, 6′- dibromoindigo) formed by vacuum evaporation. Tyrian purple is an ambipolar organic semiconductor with an optical band-gap of 1, 9 eV and electron and hole mobilities of 0, 4 cm2/Vs, which forms rectifying junctions with p-doped silicon. Even though the band-gap of both materials in the heterojunction is relatively high, our devices show sub silicon- bandgap IR sensitivity up to 2500 nm with responsivity of ~5 mA/W in the telecom C-band. Finally, we show that micro- and nano- structuring of silicon substrates prior to vacuum evaporation of organic layer significantly improves the responsivity of hybrid silicon-organic photodiodes.

silicon; organic semiconductor; hybrid; heterojunction; optoelectronic; device

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