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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Applications of Single Frequency Blue Lasers
摘要： Gallium nitride (GaN) sources are becoming a regular part of today’s world and are now key devices for lighting infrastructures, communications systems and quantum applications, amongst others. In particular, many applications have seen the shift from LEDs to laser diodes to make use of higher powers, higher bandwidths and increased transmission distances. Laser communication systems are well established, however there are applications where the ability to select a single emitted wavelength is highly desirable, such as quantum atomic clocks or in filtered communication systems. Distributed feedback (DFB) lasers have been realised emitting at a single wavelength where the grating structure is etched into the sidewall of the ridge. The main motivation in developing these lasers is for the cooling of ions in atomic clocks; however their feasibility for optical communications is also explored. Narrow linewidth lasers are desirable and this paper will explore how this is achieved. Data rates in excess of 1 Gbit/s have also been achieved in a directly modulated, unfiltered system. These devices lend themselves towards wavelength division multiplexing and filtered optical communications systems and this will be analysed further in the work presented here.
关键词： gallium nitride,optical atomic clocks,optical communications,distributed feedback lasers
更新于2025-09-19 17:13:59
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2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Foura??Terminal Tandems with Silicon and CIGS
摘要： Wide-bandgap perovskite solar cells (PSCs) with optimal bandgap (Eg) and high power conversion efficiency (PCE) are key to high-performance perovskite-based tandem photovoltaics. A 2D/3D perovskite heterostructure passivation is employed for double-cation wide-bandgap PSCs with engineered bandgap (1.65 eV ≤ Eg ≤ 1.85 eV), which results in improved stabilized PCEs and a strong enhancement in open-circuit voltages of around 45 mV compared to reference devices for all investigated bandgaps. Making use of this strategy, semitransparent PSCs with engineered bandgap are developed, which show stabilized PCEs of up to 25.7% and 25.0% in four-terminal perovskite/c-Si and perovskite/CIGS tandem solar cells, respectively. Moreover, comparable tandem PCEs are observed for a broad range of perovskite bandgaps. For the first time, the robustness of the four-terminal tandem configuration with respect to variations in the perovskite bandgap for two state-of-the-art bottom solar cells is experimentally validated.
关键词： tandem solar cells,copper indium gallium diselenide,2D perovskites,3D perovskites
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - A micro-concentrator photovoltaic module incorporating a bifacial silicon solar cell for direct and diffuse light capture
摘要： In this paper, we report findings from a micro CPV module, employing 170 μm GaAs-based 2J CPV cells, assembled on glass substrates using micro-transfer printing. The CPV array uses all-glass lens arrays to focus the light with a geometric concentration ratio of 740 suns, and a bifacial, mono-crystalline silicon solar cell behind the substrate to capture the diffuse component of the light. We found that the diffuse capture creates a significant performance boost over CPV alone, and study the role of bifacial capture on the overall performance. The highest combined efficiency with respect to global normal irradiance was 25.4% for the module, measured by outdoor testing in Washington, DC.
关键词： Transfer printing,Photovoltaic cells,Gallium arsenide
更新于2025-09-19 17:13:59
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Local atomic structure of the GaN-side of the Al2O3/GaN interface revealed by X-ray absorption spectroscopy
摘要： The interface between a gate insulator (Al2O3) and a semiconductor (GaN) was investigated via surface-sensitive Ga K-edge extended X-ray absorption fine structure spectroscopy, achieved by detecting the Ga LMM Auger electrons originated from the Ga K-shell absorption. This GaN-side interface study was conducted on Al2O3 thin films formed via atomic layer deposition. The determined atomic structures revealed GaN crystalline changes and the formation of Ga–O bonds due to nitrogen annealing.
关键词： Aluminum oxide (Al2O3),Interface,Post-deposition annealing (PDA),Gallium nitride (GaN),Extended X-ray absorption fine structure (EXAFS),Atomic layer deposition (ALD)
更新于2025-09-19 17:13:59
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Permanent photodoping of plasmonic gallium-ZnO nanocrystals
摘要： Donor dopants in oxide semiconductors are compensated not only by valuable electrons but also by other point defects, leading to a decrease in electric conductivity and infrared absorption. We demonstrate that the electron compensation mechanism in Ga doped ZnO nanocrystals can be promoted by photodoping. Unexpectedly, the electrons from photodoping are stable in the open air for months.
关键词： photodoping,infrared absorption,plasmonic,electron compensation,gallium-ZnO nanocrystals
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Photoluminescence Excitation Spectroscopy Characterization of Surface and Bulk Quality for Early-Stage Potential of Material Systems
摘要： Photoluminescence Excitation Spectroscopy (PLE) is a contactless characterization technique to quantify Shockley-Reed-Hall (SRH) lifetimes and recombination velocities in direct band gap experimental semiconductor materials and devices. It is also useful as to evaluate surface passivation and intermediate fabrication processes, since it can be implemented without the need for development of effective contact technologies. In this paper, we present a novel experimental PLE system for precision-based quantification of the aforementioned parameters as well as a system for which absolute PLE characterization may occur. Absolute PLE measurements can be used to directly calculate VOC for new photovoltaic (PV) material systems and devices. Key system capabilities include a continuous excitation spectrum from 300 nm –1.1 μm, automated characterization, up to 1 nm wavelength resolution (up to 60x higher than prior work), and a reduced ellipsometry requirement for post-processing of data. We utilize a GaAs double heterostructure (DH) and an InP crystalline wafer as calibration standards in comparison with data from an LED-based PLE to demonstrate the validity of the results obtained from this new system.
关键词： photovoltaic cells,indium phosphide,charge carrier lifetime,gallium arsenide,photoluminescence
更新于2025-09-19 17:13:59
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Multi-Energy Valley Scattering Characteristics for a SI-GaAs-Based Terahertz Photoconductive Antenna in Linear Mode
摘要： In this paper, the relationship between the terahertz radiation and the spatial distribution of photogenerated carriers under different bias electric field is studied. Terahertz pulses and the photocurrent of SI-GaAs photoconductive antenna are measured by the terahertz time-domain spectroscopy system. The occupancy rate for photogenerated carriers for different energy valleys is obtained by comparing the photocurrent of terahertz field integrating with respect to time with the photocurrent measured by oscilloscope. Results indicate that 93.04% of all photogenerated carriers are located in the Γ valley when the bias electric field is 3.33 kV/cm, and 68.6% of all photogenerated carriers are transferred to the satellite valley when the bias electric field is 20.00 kV/cm. With the bias electric field increasing, the carrier occupancy rate for the satellite valley tends to saturate at 72.16%. In order to obtain the carrier occupancy rate for the satellite valley and saturate value at the high bias electric field, an ensemble Monte Carlo simulation based on the theory of photo-activated charge domain is developed.
关键词： photoconductive antenna,multi-energy valley scattering,semi-insulating Gallium arsenide (SI-GaAs),terahertz time-domain spectroscopy
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Conference on Sensors and Nanotechnology (SENSORS & NANO) - Penang, Malaysia (2019.7.24-2019.7.25)] 2019 IEEE International Conference on Sensors and Nanotechnology - Effect of Front-Surface-Field and Back-Surface-Field on the Performance of GaAs Based-Photovoltaic Cell
摘要： GaAs structures are commonly used in concentrated solar cell application, whereas the active region of the cell requires front surface field (FSF) and back surface field (BSF) to complete the band diagram and to improve the conversion efficiency up to 22 % under AM 1.5 illumination condition. However, the integration of different FSF and BSF materials such as AlGaAs, InGaP and InAlP contribute to diverse performance. A fair comparison between these materials will help to optimize the performance of GaAs devices. In this work, Silvaco TCAD software was used to simulate GaAs PV cell with different FSF and BSF materials under 1-sun and 100-sun AM 1.5 illumination condition. A conversion efficiency of 24.08 % and 27.22 % was achieved with InAlP FSF layer under 1-sun and 100-sun AM 1.5 spectrum, respectively. The results obtained from this study will contribute to a better understanding on the effect of FSF and BSF layers while obtaining the optimum FSF and BSF material for the GaAs-based photovoltaic cell.
关键词： BSF,Silvaco TCAD,Gallium Arsenide cell,FSF
更新于2025-09-16 10:30:52
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Microwave assisted synthesis of CuInGaSe2 quantum dots and spray deposition of their composites with graphene oxide derivatives
摘要： In this contribution, we explore a spray deposition technique to prepare thin films based on nanocomposites of graphene oxide (GO) or reduced graphene oxide (rGO) with CuInGaSe2 quantum dots (QD) synthesized by a microwave-assisted method. Small nanocrystals in the tetragonal phase and emitting light at 650 nm were obtained. Water-based solutions of the nanocomposites were sprayed onto transparent conductive glass substrates using an automated ultrasonic spray system and the resulting thin films were evaluated with respect to their morphological and electrochemical properties. The distribution and organization of the graphene sheets in the composites were affected by the interaction between the nanocrystals and GO or rGO, which also interfered on the electronic properties. In addition, we demonstrated a possible application of the thin film based on the rGO-QD composite as a counter electrode in dye-sensitized solar cells.
关键词： copper indium gallium selenide,dye-sensitized solar cell,graphene oxide,microwave assisted synthesis,spray deposition,reduced graphene oxide
更新于2025-09-16 10:30:52
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Complementary metal oxide semiconductor (CMOS) compatible gallium arsenide metal-semiconductor-metal photodetectors (GaAs MSMPDs) on silicon using ultra-thin germanium buffer layer for visible photonic applications
摘要： The monolithic integration of III–V materials on silicon appears as the most promising, cost-effective, and versatile method for next-generation optoelectronic devices. Here, we report on GaAs metal-semiconductor-metal photodetectors integrated on an Si substrate by metal-organic chemical vapor deposition. The device architecture is based on a GaAs active layer grown on Si via ultrathin, low-temperature Ge buffer layers. The Ge-on-Si acts as a “virtual” substrate to reduce the overall structural defects in the GaAs device layers. The metal-semiconductor junction characteristics were optimized to effectively suppress the dark current and passivate the interface defects. This was achieved through the insertion of an ultrathin Al2O3 interlayer at the metal/GaAs interface. The results show that a Schottky barrier height of 0.62 eV and 0.8 eV for electrons and holes, respectively, can be achieved. Circular devices with diameters ranging from 30 to 140 μm were fabricated. The measured room temperature dark current is ～48 nA for an applied reverse bias of 1.0 V and a device diameter of 30 μm. Additionally, the GaAs metal-semiconductor-metal structure exhibited a remarkable photoresponsivity and detectivity values of (0.54 ± 0.15) A/W and ～4.6 × 1010 cm Hz1/2 W?1 at 5 V reverse bias, 850 nm, respectively. The proposed method offers great potential for the monolithic integration of GaAs on an Si platform. Furthermore, this technique can be extended to other III–V materials and lattice mismatched systems for high-performance multiple band optoelectronics.
关键词： gallium arsenide,visible photonic applications,metal-semiconductor-metal photodetectors,germanium buffer layer,CMOS
更新于2025-09-16 10:30:52