Enhanced near-infrared response of nano- and microstructured silicon/organic hybrid photodetectors

Abstract

Heterojunctions between an organic semiconductor and silicon are an attractive route to extending the response of silicon photodiodes into the near infrared (NIR) range, up to 2000 nm. Silicon-based alternatives are of interest to replace expensive low band-gap materials, like InGaAs, in telecommunications and imaging applications. Herein, we report on the significant enhancement in NIR photodetector performance afforded by nano- and microstructuring of p-doped silicon (p-Si) prior to deposition of a layer of the organic semiconductor Tyrian Purple (TyP). We show how different silicon structuring techniques, namely, electrochemically grown porous Si, metal-assisted chemical etching, and finally micropyramids produced by anisotropic chemical etching (Si μP), are effective in increasing the NIR responsivity of p-Si/TyP heterojunction diodes. In all cases, the structured interfaces were found to give photodiodes with superior characteristics as compared with planar interface devices, providing up to 100-fold improvement in short-circuit photocurrent, corresponding with responsivity values of 1–5 mA/W in the range of 1.3–1.6 μm. Our measurements show this increased performance is neither correlated to optical effects, i.e., light trapping, nor simply to geometric surface area increase by micro- and nanostructuring. We conclude that the performance enhancement afforded by the structured p-Si/organic diodes is caused by a yet unresolved mechanism, possibly related to electric field enhancement near the sharp tips of the structured substrate. The observed responsivity of these devices places them closer to parity with other, well-established, Si-based NIR detection technologies.

Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection

“…Because the dynamic energy of the initial hot electrons is proportional to the localized field enhancement and the optical absorption [51], this indicates that an increase in the interfacial area by the pyramid appears insufficient to account for the observed enhancement of the photocurrent. This mechanism is also reported by the enhanced NIR response of nano-organic and micro-pyramid Si hybrid photodetectors [52] and pyramidally shaped plasmonic concentrators with a Si/Al apex [22]. We conclude that the high photoresponsivity is caused by the enhancement of the localized electric field and the increase of optical absorption by the proposed Au NP-decorated Si pyramid structure.…”

Low‐dimensional nanomaterial/Si heterostructure‐based photodetectors

“…The detectivity was approximately 2 times higher than that of the corresponding PEDOT:PSS/n‐Si photodetector . To develop broadband Si/organic photodetectors, a p‐Si/Tyrian purple (TyP) heterojunction photodiode with significant enhancement in the NIR range was also reported . The device showed a photoresponsivity of 1 to 5 A W −1 in the spectral range from 1.3 to 1.6 μm; this significant enhancement was attributed to the increased surface area and light‐trapping effects of micro‐ and nanostructured p‐Si.…”

Large bandgap reduced graphene oxide (rGO) based n-p + heterojunction photodetector with improved NIR performance

“…Although, GaAs based PDs exhibit high performance but they use toxic precursors and are expensive due to their complicated processing. On the other hand, silicon based NIR PDs are of interest over GaAs based PDs due to the low cost and easy integration to existing silicon technology [2,3]. In general, a silicon p-n junction PD works in photovoltaic mode but has poor responsivity in NIR region because of its low absorption coefficient (7.9× 10 2 cm −1 ) in this region [4,5].…”

“…Subsequently, photoconductor operational mode as used in CMOS compatible photodiode is a preferred option to achieve high responsivity with very fast photoswitching behavior at nominal external reverse bias of 5 V [6], but it also suffers from a relatively high dark current limiting the performance of PD and requires hugely complex and costly manufacturing processes. Several efforts have been made to overcome the trade-off between the responsivity and dark current by enhancing the light absorption through introducing mid-band absorption states [7], nanostructured patterning or by forming heterojunction with Si using appropriate materials in hybrid geometry/devices [2,8,9]. Interestingly, the combination of two-dimensional (2D) materials (van der Waals materials; such as Graphene, rGO, MoS 2 , MoSe 2 , WSe 2 ) grown on conventional 3D semiconductor (Si, GaN, CdS, ZnO) is gaining importance for the design of hybrid electronic devices, since it combines the advantages of established 3D material and unique properties of 2D material [10][11][12].…”