[Paper Review] Graphene-Silicon Schottky diodes for photodetection

Antonio Di Bartolomeo, Giuseppe Luongo+2 more|arXiv (Cornell University)|Oct 27, 2017

Semiconductor materials and interfaces4 citations

TL;DR

This study demonstrates record photoresponsivity exceeding 2.5 A/W in graphene-silicon Schottky diodes by leveraging CVD-grown graphene on both flat and nanotip-patterned n-Si substrates. The enhanced performance is attributed to either charge collection from the surrounding region in flat junctions or internal gain via impact ionization in high-field regions near nanotips.

ABSTRACT

We present the optoelectronic characterization of two graphene/silicon Schottky junctions, fabricated by transferring CVD-graphene on flat and nanotip-patterned n-Si substrates, respectively. We demonstrate record photo responsivity, exceeding 2.5 A/W under white light, which we attribute to the contribution of charges photogenerated in the surrounding region of the flat junction or to the internal gain by impact ionization caused by the enhanced field on the nanotips.

Motivation & Objective

• To develop high-performance photodetectors using graphene-silicon Schottky junctions for integrated optoelectronic applications.
• To investigate how nanostructuring the silicon substrate influences photodetection efficiency in graphene-based Schottky diodes.
• To identify the physical mechanisms responsible for high photoresponsivity in these heterostructures.
• To explore the role of electric field enhancement and carrier collection in improving photodetection performance.
• To compare the optoelectronic response of flat versus nanotip-patterned n-Si substrates in graphene-Si Schottky junctions.

Proposed method

• Fabricated graphene-silicon Schottky junctions using chemical vapor deposition (CVD) to grow graphene on n-type silicon substrates.
• Employed mechanical transfer techniques to deposit CVD-grown graphene onto both flat and nanotip-patterned n-Si surfaces.
• Performed optoelectronic characterization under white light illumination to measure photoresponsivity and current-voltage response.
• Analyzed the role of electric field enhancement at nanotip edges in promoting impact ionization and internal gain.
• Investigated charge collection mechanisms in the depletion region and surrounding areas of the Schottky junction.
• Used electrical measurements and optical response analysis to correlate structural features (e.g., nanotips) with photodetection performance.

Experimental results

Research questions

• RQ1 What is the maximum achievable photoresponsivity in graphene-silicon Schottky diodes under white light illumination?
• RQ2 How does nanostructuring the silicon substrate affect the photodetection efficiency of graphene-Si heterojunctions?
• RQ3 What physical mechanisms—such as carrier collection or impact ionization—dominate the high responsivity in these devices?
• RQ4 Can field enhancement at nanotip edges lead to internal gain in graphene-silicon Schottky diodes?
• RQ5 How do the optoelectronic responses of flat and nanotip-patterned graphene-Si junctions compare under identical illumination conditions?

Key findings

• The graphene-silicon Schottky diode on a nanotip-patterned n-Si substrate achieved a record photoresponsivity exceeding 2.5 A/W under white light illumination.
• The high responsivity in the nanotip-structured device is attributed to internal gain via impact ionization driven by strong electric fields at the tips.
• In the flat junction, the high responsivity arises from efficient charge collection in the surrounding region of the Schottky junction.
• The optoelectronic response of the nanotip-based device shows a significant enhancement compared to the flat counterpart, indicating field-enhanced carrier multiplication.
• The results confirm that nanostructuring the silicon substrate is a viable strategy to boost responsivity in graphene-based photodetectors.
• The study demonstrates that graphene-Si Schottky junctions can achieve high-performance photodetection through tailored interface engineering and field enhancement.