Journal
ACS APPLIED NANO MATERIALS
Volume 4, Issue 11, Pages 11938-11948Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsanm.1c02505
Keywords
N-GQD; photodetector; EQE; responsivity; detectivity; noise equivalent power; Si nanowire
Funding
- Department of Science and Technology (DST) [DST/INSPIRE/04/2015/003152]
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In this work, a significantly improved silicon nanowire (SiNW) based broadband photodetector is obtained by utilizing the core-shell structure of SiNWs with hydrothermally processed nitrogen doped graphene quantum dots (N-GQDs). The performance of the photodetector device is greatly enhanced by enlarging the effective surface area of the SiNW/N-GQD heterostructure through controlled KOH etching of SiNWs. The combination of SiNWs with low-cost hydrothermal processed N-GQDs results in enhanced optical absorption, suppressed dark current, photomultiplication of charge carriers, and improved carrier transport and collection efficiency, leading to significantly improved external quantum efficiency (EQE) exceeding 150% in the near IR and similar to 500% at 460 nm wavelength in the visible region.
A significantly improved silicon nanowire (SiNW)based broadband photodetector is obtained in this work using the core-shell structure of SiNWs with hydrothermally processed nitrogen doped graphene quantum dots (N-GQDs). The performance of the photodetector device is enhanced significantly by enlarging the effective surface area of the SiNW/N-GQD heterostructure by controlled KOH etching of SiNWs. In combination with SiNWs, low-cost hydrothermal processed N-GQDs are used as a light absorber in the UV region and also as an emitter in the visible region which is reabsorbed by the SiNWs to enhance the device performance. The SiNW/N-GQD heterostructure photodetector exhibits a large photocurrent to dark-current ratio similar to 0.8 X 10(2) under zero bias and as high as similar to 0.5 X 10(4) under -2 V bias for 2 min KOH etching), remarkably low dark current (similar to 55 nA under -2 V bias for 2 min KOH etching and is six orders lower compared to control SiNWs device), and significantly improved external quantum efficiency (EQE) exceeding 150% in the near IR and similar to 500% at 460 nm wavelength in the visible region. Such higher EQE may arise due to the (i) enhanced optical absorption, (ii) suppressed dark current, (iii) photomultiplication of charge carriers because of the presence of trap states, and (iv) improved carrier transport and collection efficiency due to core-shell structure and nanoscale morphology control. It is expected that the reported SiNWs/N-GQDs core-shell heterostructure device might be useful for high-performance optoelectronic applications in the near future.
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