Junction investigation of graphene/silicon Schottky diodes (original) (raw)
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Journal of Physics D: Applied Physics, 2013
We demonstrate fabrication of a Schottky junction diode with direct growth graphene on n-Si by the solid phase reaction approach. Metal-assisted crystallization of a-C thin film was performed to synthesize transfer-free graphene directly on a SiO 2 patterned n-Si substrate. Graphene formation at the substrate and catalyst layer interface is achieved in presence of a Co catalytic and CoO carbon diffusion barrier layer. The as-synthesized material shows a linear current-voltage characteristic confirming the metallic behaviour of the graphene structure. The direct grown graphene on n-Si substrate creates a Schottky junction with a potential barrier of 0.44 eV and rectification diode characteristic. Our finding shows that the directly synthesized graphene on Si substrate by a solid phase reaction process can be a promising technique to fabricate an efficient Schottky junction device.
Graphene/Silicon Schottky Junction Solar Cells with High Efficiency
2019
Silicon p-n junction solar cells have a power conversion efficiency (PCE) up to 12%. Graphene, which has unique properties is an excellent material for solar cells with the potential to achieve higher PCEs. Since 2009, researchers have started to integrate CVD-graphene with Si substrates to develop Schottky junction solar cells with potentially higher PCE. However, there are several challenges remaining in designing and fabricating these cells.
2017
In this study, graphene-on-silicon process technology was developed to fabricate a power rectifier Schottky diode for efficiency improvement in high operating temperature. Trench-MOS-Barrier-Schottky (TMBS) diode structure was used to enhance the device performance. The main objective of this research was to study the effect of reduced graphene oxide (RGO) deposited on silicon surface for Schottky barrier formation and heat transfer in Schottky junction. The study showed RGO deposited on silicon as a heat spreader could help to reduce the effect of heat generated in the Schottky junction that leads to a leakage current reduction and efficiency improvement in the device. With comparison to the conventional metal silicide (titanium silicide and cobalt silicide), the leakage reduced by two-orders of magnitude when tested under high operating temperature (>100°C). TMBS rectifier diode that uses graphene-based heat spreader could produce highly reliable product able to withstand high ...
Carbon, 2018
A graphene/Si Schottky junction solar cell is commonly fabricated by using the top-window structure. However, reported devices have many drawbacks such as a small active area of 0.11 cm 2 , s-shape in the J-V curves, recombination process of charge carriers at the graphene/textured Si interface, high cost and a complex fabrication process. Here, we report a novel graphene/Si Schottky junction solar cell with a back contact-structure, which has benefits of a simpler fabrication process, lower fabrication cost, and larger active area in comparison with a device fabricated with the previous structure. Additionally, we found that the PMMA residue left on graphene surfaces is the key to eliminate the s-shape in the J-V curves. Thus, the deep UV treatment of the CVD graphene is applied within the wet transfer process to effectively remove the PMMA residue, suppress the behavior of s-shaped kink in J-V curves and enhance the solar cell efficiency. As a result, the recorded power conversion efficiency of 10% is achieved for graphene/ textured Si devices without chemical doping and anti-reflection coating, and this value is improved to 14.1% after applying chemical doping. Doped devices also show great stability and retain 84% of the efficiency after 9 days storage in air.
Advanced Materials Letters, 2017
We demonstrate a high-efficiency graphene/Si Schottky junction solar cell with an easy to fabricate graphene back-contact structure and effective chemical treatments. This device effectively overcame the current challenges associated with reported graphene/Si Schottky solar cell structures. The short-circuit current density for such a device is increased by around 20% due to the increase of the active area of this device, compared to previous graphene/Si Schottky junction solar cell devices. The undesirable s-shaped kink in J-V curves, as found in previous works, have been eliminated by using Formamide treatment for 30 min prior to an annealing process in the forming gas. The fill factor of this device is improved by 40% after this treatment, due to the effective removal of the unwanted PMMA residue. Moreover, volatile oxidant vapour and anti-reflection coating are applied within the fabrication process for this device to further improve solar cell performance. An efficiency of 9.5% has successfully been achieved for the fabricated device using the fabrication techniques developed in this work. Our device presents a viable and achievable approach to preparing low-cost and high-performance graphene/Si Schottky junction solar cells.
Graphene Schottky Junction on Pillar Patterned Silicon Substrate
Nanomaterials, 2019
A graphene/silicon junction with rectifying behaviour and remarkable photo-response was fabricated by transferring a graphene monolayer on a pillar-patterned Si substrate. The device forms a 0.11 eV Schottky barrier with 2.6 ideality factor at room temperature and exhibits strongly bias- and temperature-dependent reverse current. Below room temperature, the reverse current grows exponentially with the applied voltage because the pillar-enhanced electric field lowers the Schottky barrier. Conversely, at higher temperatures, the charge carrier thermal generation is dominant and the reverse current becomes weakly bias-dependent. A quasi-saturated reverse current is similarly observed at room temperature when the charge carriers are photogenerated under light exposure. The device shows photovoltaic effect with 0.7% power conversion efficiency and achieves 88 A/W photoresponsivity when used as photodetector.
Efficiency improvement of graphene/silicon Schottky junction solar cell using diffraction gratings
Optical and Quantum Electronics, 2020
This study investigated the performance of graphene/silicon Schottky junction solar cells and presented two structures based on graphene diffraction gratings to significantly enhance the efficiency of the cells. Rectangular and staircase graphene gratings were employed as the junction pairs for silicon. The main structure and the proposed structures were then investigated at different temperatures, silicon thicknesses, and doping levels. The results showed that graphene grating significantly increased the internal electric field and width of the depletion region compared to the main structure. Moreover, the graphenesilicon interface area was increased at the contact point, consequently decreasing the dangling bonds. These regions also act as anti-reflectors and reduce the reflection of sunlight. The efficiency of the proposed structures, thanks to the aforementioned features, has been reported to be threefold greater than the main structure. For instance, at the temperature of 300 K, doping level of 1 × 10 17 cm −3 and silicon thickness of 500 nm, the short-circuit current, open-circuit voltage, fill factor, and efficiency of the main structure were obtained as 20.3 mA/cm 2 , 0.154 V, 57.3%, and 1.8%, respectively. For the same conditions, these figures were obtained as 22.4 mA/cm 2 , 0.398 V, 73%, and 6.54% for the rectangular graphene grating, and 20.8 mA/cm 2 , 0.397 V, 73%, and 6.08% for the staircase graphene grating, respectively.
Back-to-Back Schottky Diode from Vacuum Filtered and Chemically Reduced Graphene Oxide
Indonesian Journal of Electrical Engineering and Computer Science, 2018
This paper presents fabrication of reduced graphene oxide (rGO)/silicon (Si) back-to-back Schottky diode (BBSD) through graphene oxide (GO) thin film formation by vacuum filtration and chemical reduction of the film via ascorbic acid. In order to understand and assess the viability of these two processes, process condition and parameters were varied and analyzed. It was confirmed that the GO film thickness could be controlled by changing GO dispersion volume and concentration. Filtration of 200 ml of 0.4 ppm GO dispersion produced average film thickness of 53 nm. As for the reduction process, long duration was required to produce higher reduction degree. rGO film that underwent two times reduction at before and after transfer process with concentrated ascorbic acid gave the lowest sheet resistance of 3.58 MΩ/sq. In the final part of the paper, result of the BBSD device fabrication and current-voltage characterization were shown. The formed two rGO/Si Schottky junctions in the BBSD gave barrier height of 0.63 and 0.7 eV. The presented results confirmed the viability of fabricating rGO-based device using a simple method and without requirement of sophisticated equipment.
High performance, self-powered photodetectors based on a graphene/silicon Schottky junction diode
Journal of Materials Chemistry C, 2018
In this work, we design and demonstrate a graphene/silicon (Gr/Si) van der Walls (vdW) heterostructure for high-performance photodetectors, where graphene acts as an efficient carrier collector and Si as a photon absorption layer. The Gr/Si heterojunction exhibits superior Schottky diode characteristics with a barrier height of 0.76 eV and performs well as a self-powered detector responding to 532 nm at zero bias.