Pub Date : 2019-11-01DOI: 10.1109/SSLChinaIFWS49075.2019.9019758
Guangshan Zhang, Miao Song, Rongbin Guo, Yahai Wang, Lei Liu, Jie Yang, Shichao Liu, Yi Yang
The test of microwave semiconductor chip is currently a hot topic. A miniaturized and highly integrated RF (Radio Frequency) module is designed to test microwave semiconductor chip. Similar to the design concept of synthetic instrument which has an open structure with standard bus and software defined radio, the newly designed integrated RF channel technology realize a variety of RF testing functions. It provides a small and highly integrated common hardware platform with a flexible software platform for re-development of control software. This platform is highly integrated with vector signal generation, vector signal analysis, vector network analysis and noise figure analysis, which can achieve a variety of functional test through dynamic reconfiguration and real-time loading. Multi-stage switch and coupler network are used to route reference signals and reflected signals and transmit signals for vector network analysis. The module receives and generates signals with frequency covering 100k~18GHz. It shares baseband FPGA which makes received signals simultaneously replay in generated channels. The bandwidth reaches 500MHz and supports a variety of vector modulated standards. This module provides a perfect solution to the testing system for microwave semiconductor chip.
{"title":"A Highly Integrated Multi-parameters RF Transceiver Module for Microwave Semiconductor Chip Testing","authors":"Guangshan Zhang, Miao Song, Rongbin Guo, Yahai Wang, Lei Liu, Jie Yang, Shichao Liu, Yi Yang","doi":"10.1109/SSLChinaIFWS49075.2019.9019758","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019758","url":null,"abstract":"The test of microwave semiconductor chip is currently a hot topic. A miniaturized and highly integrated RF (Radio Frequency) module is designed to test microwave semiconductor chip. Similar to the design concept of synthetic instrument which has an open structure with standard bus and software defined radio, the newly designed integrated RF channel technology realize a variety of RF testing functions. It provides a small and highly integrated common hardware platform with a flexible software platform for re-development of control software. This platform is highly integrated with vector signal generation, vector signal analysis, vector network analysis and noise figure analysis, which can achieve a variety of functional test through dynamic reconfiguration and real-time loading. Multi-stage switch and coupler network are used to route reference signals and reflected signals and transmit signals for vector network analysis. The module receives and generates signals with frequency covering 100k~18GHz. It shares baseband FPGA which makes received signals simultaneously replay in generated channels. The bandwidth reaches 500MHz and supports a variety of vector modulated standards. This module provides a perfect solution to the testing system for microwave semiconductor chip.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124935556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As the most possible substitutes for traditional incandescent bulbs, LED filament bulbs are becoming a research hotspot all over the world in recent years. The LED filament bulb has many advantages, including its similar appearance to incandescent bulbs, 360° lighting angle, high brightness, and low energy consumption. However, its price is so expensive that it cannot occupy the lighting market completely. So a big challenge of LED filament bulbs is how to reduce the cost of production. For the actual low-cost application requirements of a LED filament bulbs manufacturer, who is our customer, a translucent Al2O3 ceramic substrate has been prepared by tape casting and sintering process. We optimize the formulation of tape casting and technological process of preparation continually, in order to satisfy the needs of the customer as well as reduce the cost, finally 2# formula (1.2wt.%Ca-3wt.%Si-0.8wt.%Mg sintering additives with 95wt.% α-Al2O3 powder) is selected and used for preparing the ceramic substrate. The substrate can dramatically reduce the cost of LED filament bulbs from two aspects: materials and process. In terms of materials, the ceramic substrate is sintered by low-cost α-Al2O3 green tape at 1600°C in the air furnace, and the performance fully reaches the targets of the customer: the flexure strength is 470MPa, the light transmittance is 22%, and the fluctuation of shrinking percentage is ±0.14%. From the aspect of process, the ceramic substrate is divided into strips efficiently and conveniently, through scribing before sintering with hot knives on the flexible green tape substrate and breaking after sintering with automatic machines on the ceramic substrate. The dimensional precision of ceramic strips is very high, so the customer can employ automatic equipment for fabricating LED filament strips, not only reducing the process cost, but also increasing the production efficiency.
{"title":"Preparation of Translucent Al2O3 Ceramic Substrates for LED Filament Bulb","authors":"Yi-zheng Zhang, Ling Gao, Fengpo Yuan, Yaguang Wu, Dongsheng Wang, Caihua Ren, Hong-bo Bai","doi":"10.1109/SSLChinaIFWS49075.2019.9019787","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019787","url":null,"abstract":"As the most possible substitutes for traditional incandescent bulbs, LED filament bulbs are becoming a research hotspot all over the world in recent years. The LED filament bulb has many advantages, including its similar appearance to incandescent bulbs, 360° lighting angle, high brightness, and low energy consumption. However, its price is so expensive that it cannot occupy the lighting market completely. So a big challenge of LED filament bulbs is how to reduce the cost of production. For the actual low-cost application requirements of a LED filament bulbs manufacturer, who is our customer, a translucent Al2O3 ceramic substrate has been prepared by tape casting and sintering process. We optimize the formulation of tape casting and technological process of preparation continually, in order to satisfy the needs of the customer as well as reduce the cost, finally 2# formula (1.2wt.%Ca-3wt.%Si-0.8wt.%Mg sintering additives with 95wt.% α-Al2O3 powder) is selected and used for preparing the ceramic substrate. The substrate can dramatically reduce the cost of LED filament bulbs from two aspects: materials and process. In terms of materials, the ceramic substrate is sintered by low-cost α-Al2O3 green tape at 1600°C in the air furnace, and the performance fully reaches the targets of the customer: the flexure strength is 470MPa, the light transmittance is 22%, and the fluctuation of shrinking percentage is ±0.14%. From the aspect of process, the ceramic substrate is divided into strips efficiently and conveniently, through scribing before sintering with hot knives on the flexible green tape substrate and breaking after sintering with automatic machines on the ceramic substrate. The dimensional precision of ceramic strips is very high, so the customer can employ automatic equipment for fabricating LED filament strips, not only reducing the process cost, but also increasing the production efficiency.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124175134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-01DOI: 10.1109/SSLChinaIFWS49075.2019.9019802
Yudi Wang, L. Xia, Jinfeng Huang, R. Xu, Xiaofeng Liu
The appearance of objects varies enormously depending on light diffuseness. Conversely, the appearance of objects might be a cue to the light diffuseness. This would provide a solution for lighting designers to guess-estimate the light diffuseness levels based on the appearance of a light probe. However, the question remains whether rough probe provides additional cues about light diffuseness comparing with the smooth probes. If the answer to the last question is yes, whether different kinds of roughness performs the same. Furthermore, how the estimation of light diffuseness might be influenced by the illumination directions. To answer these questions, an appearance-matching experiment was performed, within which white spherical probes with four kinds of surface mesoreliefs were adopted and 5 illumination directions were tested. The results confirmed that observers’ abilities to match the light diffuseness were improved by the use of probes with 3D texture, which means that observers can derive light diffuseness from the additional cues provided by the texture over the rough probe. However, the results showed that the roughness has no obvious effect on diffuseness perception at illumination direction of 90° or 120° owing to the much useful information provided by the terminator of the body shadow.
{"title":"Infer light diffuseness on light probes with different kinds of mesoreliefs","authors":"Yudi Wang, L. Xia, Jinfeng Huang, R. Xu, Xiaofeng Liu","doi":"10.1109/SSLChinaIFWS49075.2019.9019802","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019802","url":null,"abstract":"The appearance of objects varies enormously depending on light diffuseness. Conversely, the appearance of objects might be a cue to the light diffuseness. This would provide a solution for lighting designers to guess-estimate the light diffuseness levels based on the appearance of a light probe. However, the question remains whether rough probe provides additional cues about light diffuseness comparing with the smooth probes. If the answer to the last question is yes, whether different kinds of roughness performs the same. Furthermore, how the estimation of light diffuseness might be influenced by the illumination directions. To answer these questions, an appearance-matching experiment was performed, within which white spherical probes with four kinds of surface mesoreliefs were adopted and 5 illumination directions were tested. The results confirmed that observers’ abilities to match the light diffuseness were improved by the use of probes with 3D texture, which means that observers can derive light diffuseness from the additional cues provided by the texture over the rough probe. However, the results showed that the roughness has no obvious effect on diffuseness perception at illumination direction of 90° or 120° owing to the much useful information provided by the terminator of the body shadow.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125552660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-01DOI: 10.1109/sslchinaifws49075.2019.9019750
{"title":"SSLChina: IFWS 2019 Title Page","authors":"","doi":"10.1109/sslchinaifws49075.2019.9019750","DOIUrl":"https://doi.org/10.1109/sslchinaifws49075.2019.9019750","url":null,"abstract":"","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129814281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Low level light therapy (LLLT) is a fast-growing technology used in noninvasive therapies which can stimulate healing and relieve pain and inflammation. The introduction of light-emitting diode (LED) devices has reduced many of the concerns associated with halogen lamp and lasers, such as expense and safety. However, many LED devices are bulky and not designed for home use. Besides, the effectiveness of the treatment by LLLT has significant variations in terms of dosimetry parameters for the used LED, such as wavelength, irradiance or power density, energy, etc. Therefore, we design a home-used multi-wavelength LED phototherapy system with the advantage of a small volume and high irradiance in this paper. By using AlN ceramic substrate and copper substrate as composite substrate, the vertical structure chip is tightly attached to the ceramic substrate circuit, then the package of the four-wavelength chip module is completed. In order to distribute the irradiance of all four different spectra over the desired target area, an optical mixing rod is used to collect the light, and the light is all reflected into the output face of the optical mixing rod through full internal reflection. Additionally, to form a light spot of 50mm in diameter at a distance of 5cm from the output surface, we design a pair of lens with a short focal length and large field of view based on Kohler illumination method. The parameters of the lens are designed by the software of ZEMAX. The hardware circuit uses the STM32F104 processor as controller and constant current drive mode to ensure the quality of LED light. An experimental prototype is established, and the irradiance and its uniformity, stability and safety of the phototherapy system are tested. The experimental results show that the maximum irradiance of the system is 115.4mW/cm2, and the uniformity reaches 88%. After the phototherapy system works for 2 hours with maximum illumination, the irradiance deviation is 6.7% and the temperature rise of the system is 19°C.
{"title":"Design of a multi - wavelength high irradiance LED phototherapy system for LLLT","authors":"Weimin Li, Zhiliang Jin, Jialin Liu, Liquan Guo, Haiyang Wang, D. Xiong","doi":"10.1109/SSLChinaIFWS49075.2019.9019817","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019817","url":null,"abstract":"Low level light therapy (LLLT) is a fast-growing technology used in noninvasive therapies which can stimulate healing and relieve pain and inflammation. The introduction of light-emitting diode (LED) devices has reduced many of the concerns associated with halogen lamp and lasers, such as expense and safety. However, many LED devices are bulky and not designed for home use. Besides, the effectiveness of the treatment by LLLT has significant variations in terms of dosimetry parameters for the used LED, such as wavelength, irradiance or power density, energy, etc. Therefore, we design a home-used multi-wavelength LED phototherapy system with the advantage of a small volume and high irradiance in this paper. By using AlN ceramic substrate and copper substrate as composite substrate, the vertical structure chip is tightly attached to the ceramic substrate circuit, then the package of the four-wavelength chip module is completed. In order to distribute the irradiance of all four different spectra over the desired target area, an optical mixing rod is used to collect the light, and the light is all reflected into the output face of the optical mixing rod through full internal reflection. Additionally, to form a light spot of 50mm in diameter at a distance of 5cm from the output surface, we design a pair of lens with a short focal length and large field of view based on Kohler illumination method. The parameters of the lens are designed by the software of ZEMAX. The hardware circuit uses the STM32F104 processor as controller and constant current drive mode to ensure the quality of LED light. An experimental prototype is established, and the irradiance and its uniformity, stability and safety of the phototherapy system are tested. The experimental results show that the maximum irradiance of the system is 115.4mW/cm2, and the uniformity reaches 88%. After the phototherapy system works for 2 hours with maximum illumination, the irradiance deviation is 6.7% and the temperature rise of the system is 19°C.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126003819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-01DOI: 10.1109/SSLChinaIFWS49075.2019.9019816
D. Hou, Congshan Dai, Yan Lu, Yandan Lin
There is ample evidence to support the hypothesis that indoor lighting environment has an impact on human affective and cognitive processes. Light distribution is one of the important aspects of the indoor lighting environment. With the development of various pendant luminaires and LED technology, both photometric and colorimetric distribution in vertical can be adjustable thus different lighting schemes can be achieved to satisfy the need for lighting design.The present study of light distribution in a real lit office conducted two parts of experiments. The aim is to discuss the impact of proportions of direct/indirect lighting on both subjective evaluation and work performance, also include the discussion of the distribution of correlated color temperature (CCT) of direct/indirect lighting in an office space.
{"title":"Effects of Illumination and Color Temperature Distribution on Subjective Perception","authors":"D. Hou, Congshan Dai, Yan Lu, Yandan Lin","doi":"10.1109/SSLChinaIFWS49075.2019.9019816","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019816","url":null,"abstract":"There is ample evidence to support the hypothesis that indoor lighting environment has an impact on human affective and cognitive processes. Light distribution is one of the important aspects of the indoor lighting environment. With the development of various pendant luminaires and LED technology, both photometric and colorimetric distribution in vertical can be adjustable thus different lighting schemes can be achieved to satisfy the need for lighting design.The present study of light distribution in a real lit office conducted two parts of experiments. The aim is to discuss the impact of proportions of direct/indirect lighting on both subjective evaluation and work performance, also include the discussion of the distribution of correlated color temperature (CCT) of direct/indirect lighting in an office space.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121575302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we develop an optimized VDMOSFET cell structure based on 4H-SiC material. In the optimized structure, two high n-doped regions are added at both sides of the JFET region. Simulation results reveal that the additional n-doped regions not only effectively limit the depletion width in JFET region at ON-state, but also could protect the oxide layer at OFF-state due to depletion expansion. As a result, the optimized structure reduces the specific ON-resistance by 18% while keeping breakdown voltage as roughly high as the conventional structure; meanwhile, the value of figure of merit increases by 22%, which exhibits a significant improvement in device performance.
{"title":"Optimized Design of 4H-SiC VDMOSFET for Low ON-resistance","authors":"Defu Yin, Zhiming Wu, Xian Zou, Yongqiang Sun, Yaping Wu, Weiping Wang, Xu Li, Junyong Kang","doi":"10.1109/SSLChinaIFWS49075.2019.9019763","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019763","url":null,"abstract":"In this work, we develop an optimized VDMOSFET cell structure based on 4H-SiC material. In the optimized structure, two high n-doped regions are added at both sides of the JFET region. Simulation results reveal that the additional n-doped regions not only effectively limit the depletion width in JFET region at ON-state, but also could protect the oxide layer at OFF-state due to depletion expansion. As a result, the optimized structure reduces the specific ON-resistance by 18% while keeping breakdown voltage as roughly high as the conventional structure; meanwhile, the value of figure of merit increases by 22%, which exhibits a significant improvement in device performance.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116597197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-01DOI: 10.1109/SSLChinaIFWS49075.2019.9019772
Ziyue Zhao, Yang Lu, Hengshuang Zhang, Chupeng Yi, Yuchen Wang, Xiao-hua Ma, Y. Hao
With the development of the microelectronics, circuit design also becomes more and more important. The circuit needs to be designed by the model, and the accuracy of the model will also determine the quality of the circuit design. In order to improve the accuracy of circuit design, it is necessary to improve the accuracy of the circuit model. This paper mainly discusses a more accurate method basing on the Angelov Model of the Gallium Nitride (GaN) based high electron mobility transistors (HEMTs). For the Angelov Model, the fitting of DC curve is the most critical. There are many parameters to fit and modify the fitting curve. Some of these parameters are of certain physical significance, while others are mainly used to improve the accuracy of curve fitting. Each parameter does not change with the bias, which will lower the accuracy of the model. In this paper, the sensitive parameters in the model are changed into a function of gate voltage and drain voltage by formula. In this way, the fitting accuracy of the model is improved. However, the improvement of the model accuracy is very limited by changing the sensitive parameters. Next, the curve is compensated by error function to improve the accuracy of the whole model. It also makes up for the defect that the Angelov Model cannot fit when the drain current is negative. In order to further improve the accuracy of the model, the weight function is used to correct the error function, which improves the fitting accuracy of the error function and makes the fitting of the output curve more accurate. Finally, the accuracy of the model was improved by 57%, which satisfied the needs of the circuit design.
{"title":"High Precision Model by Error Compensation Method based on the Angelov Model","authors":"Ziyue Zhao, Yang Lu, Hengshuang Zhang, Chupeng Yi, Yuchen Wang, Xiao-hua Ma, Y. Hao","doi":"10.1109/SSLChinaIFWS49075.2019.9019772","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019772","url":null,"abstract":"With the development of the microelectronics, circuit design also becomes more and more important. The circuit needs to be designed by the model, and the accuracy of the model will also determine the quality of the circuit design. In order to improve the accuracy of circuit design, it is necessary to improve the accuracy of the circuit model. This paper mainly discusses a more accurate method basing on the Angelov Model of the Gallium Nitride (GaN) based high electron mobility transistors (HEMTs). For the Angelov Model, the fitting of DC curve is the most critical. There are many parameters to fit and modify the fitting curve. Some of these parameters are of certain physical significance, while others are mainly used to improve the accuracy of curve fitting. Each parameter does not change with the bias, which will lower the accuracy of the model. In this paper, the sensitive parameters in the model are changed into a function of gate voltage and drain voltage by formula. In this way, the fitting accuracy of the model is improved. However, the improvement of the model accuracy is very limited by changing the sensitive parameters. Next, the curve is compensated by error function to improve the accuracy of the whole model. It also makes up for the defect that the Angelov Model cannot fit when the drain current is negative. In order to further improve the accuracy of the model, the weight function is used to correct the error function, which improves the fitting accuracy of the error function and makes the fitting of the output curve more accurate. Finally, the accuracy of the model was improved by 57%, which satisfied the needs of the circuit design.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133153703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polytype destabilization at the periphery of 4H-SiC single crystals during the initial stage of 4H-SiC bulk crystals grown on on-axis seeds by sublimation method were investigated. Optical microscopy and Raman spectroscopy, were used to study the distribution of polytypism. Three regions with different Raman peak intensity ratio (I150/I204) at the outer parts of the grown layer are distinctly observed, indicating the increase in parasitic polytype component towards the edge. The higher probability of 6H or 15R-SiC nucleation due to the higher supersaturation at the periphery could be responsible for the polytype transformation.
{"title":"Polytype Transformation in 4H-SiC single crystals grown on on-axis Seeds","authors":"Xianglong Yang, Yan Peng, Xiufang Chen, Xuejian Xie, Jinying Yu, Xiaobo Hu, Xiangang Xu","doi":"10.1109/SSLChinaIFWS49075.2019.9019806","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019806","url":null,"abstract":"Polytype destabilization at the periphery of 4H-SiC single crystals during the initial stage of 4H-SiC bulk crystals grown on on-axis seeds by sublimation method were investigated. Optical microscopy and Raman spectroscopy, were used to study the distribution of polytypism. Three regions with different Raman peak intensity ratio (I150/I204) at the outer parts of the grown layer are distinctly observed, indicating the increase in parasitic polytype component towards the edge. The higher probability of 6H or 15R-SiC nucleation due to the higher supersaturation at the periphery could be responsible for the polytype transformation.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122985246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-01DOI: 10.1109/SSLChinaIFWS49075.2019.9019813
Pan Liu, Yong Li, Xiaobin Jian, Chen Jing, Min Li, S. Ding, Guoqi Zhang
The industrial market has been growing for high-power ultraviolet (UV) LEDs in curing, water purifying, and other applications that required high light output. As a rule of thumb, LED lumen output usually drops 0.3–0.5% for each 1°C increase in temperature while operating within the typical working temperature range. Such requirements for high-power UV LED modules indicate that innovative materials and processes for module packaging are needed to reduce thermal conductivity and to ensure high reliability.In this work, UVA (wavelengths between 365–405nm) LEDs were chosen, since the increasing usage in curing equipment for drying paints, adhesives, and other curable materials. In order to reduce the thermal conductivity of UVA LED packages, a high power UV Chip on Board (COB) based LED module was simulated. Compared with traditional modules using silver-filled adhesive and metal-core printed circuit boards(MCPCB) substrate, the novel high power UV COB based module was using nano-silver material for die attach process. Such silver sintering method is emerging for high power electronics applications. Such substrate is then sintered on copper heatsink which is covered by a thin layer of graphene, for better thermal management. Such novel structure was investigated using ABAQUS software and the Heat Transfer Module. The simulation is intended to first check how much thermal conductivity reduce caused by nanosilver sinter die attach process. Secondly, the simulation will also investigate the graphene influence on the copper heatsink. Results from the simulation will show the typical structural function of a 200W LED module with reduced thermal resistance up to 7%. The module temperature with edge-to-center temperature difference will also be checked as a standard to compare the heat dissipation capacity. Besides, the simulation will provide temperatures in various parts of the LED module in steady-state conditions, as an indication for reliability.
{"title":"Thermal Simulations of a UV LED module with nanosilver sintered die attach process on graphene-coated copper substrates","authors":"Pan Liu, Yong Li, Xiaobin Jian, Chen Jing, Min Li, S. Ding, Guoqi Zhang","doi":"10.1109/SSLChinaIFWS49075.2019.9019813","DOIUrl":"https://doi.org/10.1109/SSLChinaIFWS49075.2019.9019813","url":null,"abstract":"The industrial market has been growing for high-power ultraviolet (UV) LEDs in curing, water purifying, and other applications that required high light output. As a rule of thumb, LED lumen output usually drops 0.3–0.5% for each 1°C increase in temperature while operating within the typical working temperature range. Such requirements for high-power UV LED modules indicate that innovative materials and processes for module packaging are needed to reduce thermal conductivity and to ensure high reliability.In this work, UVA (wavelengths between 365–405nm) LEDs were chosen, since the increasing usage in curing equipment for drying paints, adhesives, and other curable materials. In order to reduce the thermal conductivity of UVA LED packages, a high power UV Chip on Board (COB) based LED module was simulated. Compared with traditional modules using silver-filled adhesive and metal-core printed circuit boards(MCPCB) substrate, the novel high power UV COB based module was using nano-silver material for die attach process. Such silver sintering method is emerging for high power electronics applications. Such substrate is then sintered on copper heatsink which is covered by a thin layer of graphene, for better thermal management. Such novel structure was investigated using ABAQUS software and the Heat Transfer Module. The simulation is intended to first check how much thermal conductivity reduce caused by nanosilver sinter die attach process. Secondly, the simulation will also investigate the graphene influence on the copper heatsink. Results from the simulation will show the typical structural function of a 200W LED module with reduced thermal resistance up to 7%. The module temperature with edge-to-center temperature difference will also be checked as a standard to compare the heat dissipation capacity. Besides, the simulation will provide temperatures in various parts of the LED module in steady-state conditions, as an indication for reliability.","PeriodicalId":315846,"journal":{"name":"2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114705837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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