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Structural and Optical Properties of AlN/GaN and AlN/AlGaN/GaN thin films on Silicon Substrate prepared by Plasma Assisted Molecular Beam Epitaxy (MBE)
摘要： In this study, the Aluminium Nitride/Gallium Nitride (AlN/GaN) layers and Aluminium Nitride/Aluminium Gallium Nitride/Gallium Nitride (AlN/AlGaN/GaN) layer heterostructures were successfully created using technique known as plasma-assisted molecular beam epitaxy (MBE) on silicon substrate. Gallium (7N) and Aluminium (6N5) of high purity were used to grow GaN, AlN and AlGaN respectively. The structural and optical properties of the prepared AlN/GaN and AlN/AlGaN/GaN layer heterostructures were investigated by means of atomic force microscope (AFM), X-ray diffraction (XRD), photoluminescence spectroscopy (PL) and Raman spectroscopy. AFM measurement demonstrated that the root mean square of surface roughness for AlN/GaN and AlN/AlGaN/GaN heterostructures are 3.677 nm and 10.333 nm respectively. XRD data indicated that the samples have typical diffraction pattern of hexagonal structure. Raman spectra revealed all four Raman-active modes present inside both samples. PL spectra data showed the yellow luminescence which corresponds to the deep energy levels due to imperfections of AlN did not appear. Thus, PL observation indicated that the thin film of AlN/GaN and AlN/AlGaN/GaN layers have good optical quality and looks promising for various target applications in optoelectronics, photovoltaic and radiofrequency applications.
关键词： silicon,thin film,MBE,Aluminium Nitride,Gallium Nitride,Aluminium Gallium Nitride
更新于2025-09-23 15:23:52
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Efficient broadband light absorption in thin-film a-Si solar cell based on double sided hybrid bi-metallic nanogratings
摘要： Thin film solar cells (TFSCs) suffer from poor light absorption due to their small thickness, which limits most of their practical applications. Surface plasmons generated by plasmonic nanoparticles offer an opportunity for a low-cost and scalable method to optically engineer TFSCs. Here, a systematic simulation study is conducted to improve the absorption efficiency of amorphous silicon (a-Si) by incorporating double sided plasmonic bi-metallic (Al–Cu) nanogratings. The upper pair of the gratings together with an antireflection coating are responsible for minimizing the reflection losses and enhancing the absorption of low wavelength visible light spectrum in the active layer. The bottom pairs are accountable for increasing the absorption of long wavelength photons in the active layer. In this way, a-Si, which is a poor absorber in the long wavelength region, is now able to absorb broadband light from 670–1060 nm with an average simulated absorption rate of more than 70%, and improved simulated photocurrent density of 22.30 mA cm?2, respectively. Moreover, simulation results show that the proposed structure reveals many other excellent properties such as small incident angle insensitivity, tunability, and remarkable structural parameters tolerance. Such a design concept is quite versatile and can be extended to other TFSCs.
关键词： amorphous silicon,Thin film solar cells,plasmonic nanoparticles,bi-metallic nanogratings,light absorption
更新于2025-09-23 15:21:01
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The impacts of LPCVD wrap-around on the performance of n-type tunnel oxide passivated contact c-Si solar cell
摘要： In this paper, Tunnel Oxide Passivated Contact (TOPCon) silicon solar cells with the industrial area (244.32cm2) are fabricated on N-type silicon substrates. Both the ultra-thin tunnel oxide layer and phosphorus doped polycrystalline silicon (polysilicon) thin film are prepared by the LPCVD system. The wrap-around of polysilicon is observed on the surface of borosilicate glass (BSG). The polysilicon wrap-around can form a leakage current path, thus degrades the shunt resistance of solar cells, and leads to the degradation of solar cell efficiency. Different methods are adopted to treat the polysilicon wrap-around and improve shunt resistance of solar cells. The experimental results indicate that a chemical etching method can effectively solve the problem of polysilicon wrap-around and improve the performance of solar cells. Finally, a conversion efficiency of 22.81% has been achieved by our bifacial TOPCon solar cells, with Voc of 702.6 mV, Jsc of 39.78 mA/cm2 and FF of 81.62 %.
关键词： LPCVD,wrap-around,Tunnel oxide passivated contact,polycrystalline silicon thin film
更新于2025-09-23 15:21:01
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Pixel Circuit With Leakage Prevention Scheme for Low-Frame-Rate AMOLED Displays
摘要： This work proposes a new pixel circuit for active-matrix organic light-emitting (AMOLED) smartwatch displays with a low frame rate. Within the long emission period, the leakage current of a low-temperature polycrystalline silicon thin-film transistor (LTPS TFT) is reduced to suppress the distortion of the driving voltage at the gate node of the driving TFT. Based on the measured electrical characteristics of a fabricated p-type LTPS TFT, the HSPICE model is established to verify the feasibility of the proposed circuit. The analytical results indicate that the relative OLED current error rates are all below 4.73%, as the threshold voltage of TFT varies by ±0.5 V. Notably, the OLED current varies by only 2.94% during the emission period of 66.7 ms at a medium gray level, demonstrating the effectiveness of the leakage prevention scheme.
关键词： low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs),Active-matrix organic light-emitting diode (AMOLED),leakage current prevention
更新于2025-09-16 10:30:52
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Comprehensive analysis of blue diode laser-annealing of amorphous silicon films
摘要： The low temperature polycrystalline silicon (LTPS) method has proved to be a technical breakthrough, accomplishing semiconductor thin films with remarkable mobility for a range of high-performance displays, including liquid crystal display and organic light emitting diodes. However, utilizing a conventional excimer laser source for LTPS incurs high cost. In this paper, we demonstrate a comprehensive analysis of the crystallization mechanism of a-Si film (94 nm) and the thermal deformation of the glass substrate induced by Blue diode Laser Annealing (BLA). BLA provides high quality laterally grown crystals over 4 μm × 10 μm on glass substrates, which were examined by optical microscopy, scanning electron microscopy, and Raman spectroscopy. In addition, the permanent deformation introduced by the annealing process is numerically modeled, instantiating how to control the heat conduction from the thin film that affects the substrate. Our findings reveal that the permanent thermal deformation depth that can be obtained is comparable to the roughness of the silicon film for the optimum scanning speed and laser power. The combination of both experimental and numerical results elucidates the manifested physical mechanisms during the BLA process and provides the guidelines to improve the experimental parameters of this process.
关键词： Lateral grain growth,Glass deformation,Silicon thin film,Low Temperature Polycrystalline Silicon (LTPS),Blue diode laser
更新于2025-09-12 10:27:22
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Long-Term Behavior of Hydrogenated Amorphous Silicon Thin-Film Transistors Covered With Color Filters for Use in Optical Sensors
摘要： This work investigates the long-term behavior of photo thin-film transistors (TFTs) that are covered with color filters and based on hydrogenated amorphous silicon (a-Si:H) technology. Based on the electrical characteristics and the optical responses of these TFTs as measured under different stress conditions, a new method for driving a photo TFT with a negative gate-source voltage is proposed to suppress the degradation of the photocurrent. The effectiveness of the newly proposed method is verified using our previously developed white-light photocurrent gating (WPCG) structure, the measurement of photocurrents, and the established models of red, green, and blue photo TFTs. An accelerated lifetime test of the fabricated circuit was carried out at 70 ?C and under the illumination of ambient light for 504 hours, demonstrating that the proposed method improves the long-term reliability of optical sensors.
关键词： optical sensor,Hydrogenated amorphous silicon thin-film transistor,long-term reliability
更新于2025-09-11 14:15:04
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New Advances in Hydrogenation Processes - Fundamentals and Applications || Hydrogenation of Polycrystalline Silicon Thin‐Film Transistors
摘要： In this chapter, the behavior of hydrogen (H) atoms in polycrystalline silicon (poly‐Si) thin film is investigated in detail in order to evaluate and improve the quality of hydrogenated poly‐Si thin films. Hydrogenation drastically improves the Hall effect mobility, whereas excessive hydrogenation tends to degrade it. The catalytic method is useful to inhibit excessive hydrogenation and damage suffered by the electric‐field acceleration of charged particle. The H‐termination of the dangling bonds at grain boundaries can be observed indirectly or directly by chemical etching and Raman microscopy. This H‐termination appeared as the 2000?cm‐1 local vibrational mode (LVM) in Raman spectra. The breaking of the Si–Si bonds by hydrogenation was detected as the 2100?cm‐1 LVM. In addition, the defects generated in the plasma process exhibit multiple fine LVMs after hydrogenation. Moreover, we investigated the hydrogenation of low‐temperature (LT) poly‐Si thin‐film transistors (TFTs) from the perspective of the gettering phenomenon. The most important parameter for effective hydrogenation using H gas annealing is the rate of cooling from 400°C.
关键词： Raman scattering,hydrogenation,thin film,polycrystalline silicon,thin‐film transistors
更新于2025-09-10 09:29:36
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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - Fabrication of P-Type Microcrystalline Silicon Thin Film by Magnetron Sputtering and Copper Induced Crystallization
摘要： P-type micro-crystalline Silicon thin film was realized by magnetron sputtering and copper-induced crystallization for photovoltaic applications. Firstly, amorphous Silicon film was deposited by direct current magnetron sputtering from highly-doped single crystalline Si target. Then it was crystallized by copper-induced crystallization in nitrogen atmosphere with the annealing temperatures ranges from 450 to 950 °C. The micro-crystalline Silicon thin film was characterized by X-ray diffraction and Ramon spectrometry. Its grain size and crystallization ratio were approximately 20 nm and 93%, respectively. Finally, a PN junction solar cell was fabricated by creating the P-type microcrystalline Si thin film (as the P region) on a highly-doped N-type Silicon wafer (as N region). The fabricated device showed the good rectification characteristics of a typical diode where under dark condition it represented the rectification ratio of 150 and reverse saturation current density of 9 μA.cm-2. The fabricated solar cell showed a significant photovoltaic effect under AM 1.5G illumination conditions. The highest photovoltaic conversion efficiency of 2.1%, with the open-circuit voltage of 416 mV and short-circuit current density of 13.3 mA/cm2, was measured from the sample fabricated by the optimal process.
关键词： magnetron sputtering,microcrystalline silicon thin film,copper induced crystallization,characterization
更新于2025-09-09 09:28:46