Role of Interfacial Oxide in High-Efficiency Graphene–Silicon Schottky Barrier Solar Cells

Song, Yi; Li, Xinming; Mackin, Charles; Zhang, Xu; Fang, Wenjing; Palacios, Tomás; Zhu, Hongwei; Kong, Jing

doi:10.1021/nl505011f

Cited by 420 publications

(286 citation statements)

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“…The reduced photocurrent responsivity R c ( fig.5b) and increased photovoltage responsivity R v ( fig.5c) for low light intensities can be qualitatively explained due to the presence of the interfacial oxide layer in the GIS device according to the suggestion in [47]. Photogenerated holes build-up at the interface due to the presence of the interfacial oxide layer [47].…”

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Towards substrate engineering of graphene–silicon Schottky diode photodetectors

et al. 2018

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Graphene-Silicon Schottky diode photodetectors possess beneficial properties such as high responsivities and detectivities, broad spectral wavelength operation and high operating speeds. Various routes and architectures have been employed in the past to fabricate devices. Devices are commonly based on the removal of the silicon-oxide layer on the surface of silicon by wet-etching before deposition of graphene on top of silicon to form the graphene-silicon Schottky junction. In this work, we systematically investigate the influence of the interfacial oxide layer, the fabrication technique employed and the silicon substrate on the light detection capabilities of graphene-silicon Schottky diode photodetectors. The properties of devices are investigated over a broad wavelength range from near-UV to short-/mid-infrared radiation, radiation intensities covering over five orders of magnitude as well as the suitability of devices for high speed operation. Results show that the interfacial layer, depending on the required application, is in fact beneficial to enhance the photodetection properties of such devices. Further, we demonstrate the influence of the silicon substrate on the spectral response and operating speed. Fabricated devices operate over a broad spectral wavelength range from the near-UV to the short-/mid-infrared (thermal) wavelength regime, exhibit high photovoltage responses approaching 10 6 V/W and short rise-and fall-times of tens of nanoseconds.Graphene is an appealing material for ultrafast and broadband photodetection applications due to its high charge carrier mobility [1, 2] and ultra-wide spectral absorption range [3,4]. The initial examples of graphene photodetectors are mostly based on metal-graphene (MG) junctions [5][6][7] and graphene p-n junction architectures [8][9][10]. Despite their broadband operation at ultrafast speeds [11], they generally exhibit low responsivities (limited to a few mAW −1 ) due to the intrinsically low optical absorption of monolayer graphene (2.3%) [12]. Further, the small photoactive area limits their use for realworld applications [9,10,13]. Recently, there is a surge of interest in using graphene to replace the metal electrode on semiconductor surfaces to realize Schottky diodes [17]. A further benefit of the graphene-silicon Schottky platform is its simple architecture, suitability for large scale fabrication and the potential for integration into the back end-of-line (BEOL) CMOS processing [11,55]. Particularly in photodetection applications, the G-Si diode provides an efficient hybrid platform where both graphene and silicon can be used as absorbing materials for different wavelength ranges [36]. Devices shows high responsivities comparable to commercial silicon photodiodes for wavelength ranges with photon energies above the silicon bandgap which is enabled by the high optical transmittance of graphene of more than 97% [27,36]. Detection of radiation with energies below the silicon band gap is enabled by the broadband absorption of graphene [25,26]. Respon...

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confidence: 89%

“…Photogenerated holes build-up at the interface due to the presence of the interfacial oxide layer [47]. The oxide layer poses a tunneling barrier for charge carriers and an electric field facilitates the tunneling of charge carriers through this barrier.…”

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confidence: 99%

Towards substrate engineering of graphene–silicon Schottky diode photodetectors

et al. 2018

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“…[4,5] These heterostructures can act as rectifiers, potential barrier modulators, photodetectors, photovoltaic devices, chemical sensors, etc. [6][7][8][9][10][11][12] Even though GS Schottky diodes are relatively simple to fabricate, their performance is limited by the various factors which can be measured by the ideality factor (η). Previous studies report unusually wide-range ideality factors of the GS devices, η = 1.1-33.5.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies report unusually wide-range ideality factors of the GS devices, η = 1.1-33.5. [6][7][8][9][10][11][12] To design and implement efficient practical GS www.advelectronicmat.de the above-mentioned effects. From the analysis of experimental data and Raman spectroscopic study, we extracted and confirmed various physical parameters such as the voltagedependent carrier concentration of graphene, interface state density, and ideality factors.…”

Section: Introductionmentioning

confidence: 99%

Origin of Voltage‐Dependent High Ideality Factors in Graphene–Silicon Diodes

Park

Choi

2017

Adv Elect Materials

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devices, the hurdle should be overcome by identifying the origin. However, the origin of the wide-range ideality factor was not yet been fully elucidated.The ideality factor is a measure of how efficiently an applied bias is delivered to the junction of the device. The ideality factor of GS devices can be influenced by both voltage-independent serial resistance and voltage-dependent attributes such as interface state and quantum capacitance. Thus, one can expect that the ideality factor changes with applied bias voltage.First of all, when a bias voltage is applied to a GS junction, the Fermi level of 2D graphene changes significantly in contrast to typical metal-oxide-semiconductor (MOS) devices due to the far less density of states of graphene compared to that of 3D metal. As a result, the effective Schottky barrier height and the resistance of graphene change with bias voltage. This directly influences the GS device performance and the ideality factor.Second, a peculiar issue related to the GS devices is the un avoidable wet graphene transfer process on a cleaned silicon wafer. During this process, oxidation of silicon occurs naturally. As a result, the GS devices inevitably have a native interfacial oxide layer between graphene and silicon although it may be very thin. This interfacial oxide layer directly influences the performance of GS devices. Although the layer can act as a tunneling barrier, which may enhance the effective potential barrier height, this effect has often been ignored because the layer is thin enough to assume that the transport property is largely governed by the semiconductor rather than limited by the tunneling.Third, the truncated silicon surface has high density of surface states. The surface states can exist as interface states of GS devices. The interface states can be equilibrated with silicon itself or with the graphene and this depends on the thickness of the interfacial oxide layer. Due to the very thin native oxide layer, one can expect that the silicon interface state can be mostly equilibrated with graphene rather than silicon itself. But this has not been confirmed yet.In this study, first we extract the voltage-dependent ideality factors of graphene-silicon Schottky diodes from their I-V characteristics based on Schottky emission theory. [13][14][15] We then compare the ideality factors with those obtained from the impedance spectra. [16,17] We designed an equivalent circuit model for analysis of impedance spectra accounting for Undoubtedly graphene-silicon (GS) heterostructure devices will play significant roles as future rectifiers, potential barrier modulators, photodetectors, photovoltaic devices, biochemical sensors, and so on. However, typical GS devices suffer from unusually wide-range voltage-dependent high ideality factors (η = 1.1-33.5). To overcome this hurdle, the origin of this wide-range voltage-dependent ideality factor should first be identified but this has not yet been fully studied. This study focuses on identifying the origin using impedance spectroscop...

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“…A rapid thermal annealing process was applied to clean the Si surface and form a thin oxide layer. The thin oxide layer is effective for reducing the reverse saturation current and thus improves the device property [19]. Silicon was used with a thin oxide layer, which is the same for all the devices [20].…”

Section: Methodsmentioning

confidence: 99%

Hybrid Structures of ITO-Nanowire-Embedded ITO Film for the Enhanced Si Photodetectors

Kim

Lee

Kim

2018

Journal of Nanomaterials

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A high-performance silicon UV photodetector was achieved by using a hybrid of a film with nanowires. Electrically conductive and optically transparent indium-tin oxide (ITO) was deposited to form an ITO film or ITO nanowire (NW) on a Si substrate, resulting in a heterojunction. The ITO-film device is stable with a low-leakage current. Meanwhile, the ITO NWs demonstrated an excellent capability to collect photogenerated carriers. The hybrid ITO (NWs on a film)/Si photodetector demonstrates a fast UV reactive time of 1.6 ms among Si-based photodetectors. We may find a means of enhancing the photoelectric performance capabilities of devices beyond the limits of conventional Si via the adoption of functional designs. Moreover, the use of a homogeneous material for the structuring of films and nanowires would offer a remarkable advantage by reducing both the number of fabrication steps and the cost.

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Role of Interfacial Oxide in High-Efficiency Graphene–Silicon Schottky Barrier Solar Cells

Cited by 420 publications

References 33 publications

Towards substrate engineering of graphene–silicon Schottky diode photodetectors

Towards substrate engineering of graphene–silicon Schottky diode photodetectors

Origin of Voltage‐Dependent High Ideality Factors in Graphene–Silicon Diodes

Hybrid Structures of ITO-Nanowire-Embedded ITO Film for the Enhanced Si Photodetectors

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