A Broadband Photoelectronic Detector in a Silicon Nanopillar Array with High Detectivity Enhanced by a Monolayer Graphene

Abstract

To meet the fast-growing need for broad applications in remote sensing, novel optoelectronic devices with high detectivity in full bands and room temperature operation are urgently desired. This paper reports our progress in developing a specially designed photovoltaic detector by integrating a monolayer graphene onto a silicon-based nanopillar array standing on a p–n junction. Optoelectronic measurements of the fabricated detectors show that the monolayer graphene plays a critical role in device performance. Compared with the one without the graphene covering, the new device demonstrates significant improvements in the specific detectivity of 1.43 × 1013 Jones and the responsivity exceeding ∼106 V/W with a reduced leakage current corresponding to a quantum efficiency of 74.8% at 860 nm wavelength. Moreover, such sensing performance remained unaffected over the entire band from 450 to 1100 nm at room temperature, which is suitable for broadband imaging applications.

Remarkable Noise Reduction in High-Stability Self-Powered Doped Graphene/Si-Quantum Dot Broadband Photodetectors by Using Graphene Quantum Dots as an Interlayer

“…In contrast, the EQE looks very flat from λ = ∼970 nm down to ∼400 nm because the decrease of R at the lower λ is compensated by the decrease of λ itself, as clearly seen in the EQE formula: EQE = ( hc / q ) (1/λ)­R, where h is the Planck constant and q is the electron charge. Especially, the EQE reaches ∼90% in the visible range (∼400 to ∼900 nm), much larger than those previously known for GR/Si-junction-based PDs, ,,,,,,− as summarized in Table . In contrast, the R /EQE of the PD counterpart with pristine (undoped)-GR TCE showed a relatively low 0.34 A W –1 /71% at λ = 600 nm (Figure S5), respectively, because of the high sheet resistance (640 Ω/sq) of the pristine GR despite the perfect transmittance.…”

“…Nevertheless, the photoresponse is limited in its further enhancement owing to the large leakage current caused by relatively high-density defect states at the GR/Si interface . To overcome this problem, many researchers have made a lot of efforts to improve the performance by giving varieties to the basic structure of the GR/Si heterojunction. − Si quantum dots (SiQDs)-embedded SiO 2 (SiQDs:SiO 2 ) has been highly attractive for photonic device applications, thanks to distinctive properties such as stronger light absorption and faster photo-sensing than bulk Si. Particularly, SiQDs:SiO 2 was well applied in solar cells and PDs. − The optoelectronic properties of the GR/Si heterojunction proved to be improved by employing SiQDs:SiO 2 between GR and a Si wafer in previous studies, ,− resulting from the improvement of the band profiles at the GR/Si interface.…”

Facilely Achieved Self‐Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100%

“…Within this framework, the low processing cost and the ease of integration have inspired the development of various self-biased Si heterojunctions with high performance. [1][2][3][4][5][6] However, the simply constructed heterojunction silicon photodiodes invariably exhibit an external quantum efficiency (EQE) significantly below 100%. [7][8][9][10] The advent of black silicon (b-Si) has led to the development of innovative photodiodes and solar cells that yield high quantum efficiency over a broadband of wavelengths, having elegant combinations of advanced surface passivation technologies, light trapping/antireflection structures, and device constructs.…”

“…Meanwhile, various alternative strategies have drawn recent research focus toward the development of a single contact material that can be simply integrated within nanostructured Si morphology to achieve high quantum efficiency heterojunctions. [4,[18][19][20][21] For example, Liang et al, reported a selfbiased poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/Si nanowire photodetector with 60-80% EQE from 400 to 900 nm. [21] Notwithstanding these reported advances, present-day heterojunction photodetectors continue to fall short of achieving unity EQE across the visible and nearinfrared (NIR) wavelengths due to nonideal absorption, nonoptimal charge carrier transport, photocarrier recombination losses in bulk and at interfaces, severe parasitic optical absorption in various contact layers and more.…”

High performance of a broadband room-temperature Si detector beyond the cut-off wavelength

“…12 A graphene/Si nanopillar array exhibited a broadband detection in 450-1100 nm with photovoltaic responsivity of B106 V W À1 at 860 nm. 13 Moreover, a PdSe 2 /Si nanowire array exhibited an ultrabroad spectrum response range of 0.2-4.6 mm with a high responsivity of 726 mA W À1 . 14 According to the reported results, silicon-based broadband detectors are mainly realized by combining two dimensional materials to make heterojunction detectors, which have the problems of instability and low responsivity.…”