Pub Date : 2016-11-01DOI: 10.1109/IFWS.2016.7803765
Song Yang, Lei Lei, Kun Yu, Xuhui Wang, Ting Zhou, Xing Lu, Anping Zhang
We report on a novel vertical GaN trench structure using PEALD-AlN/GaN hetero-structure for the first time. Through characterizing PEALD-Al2O3/AlN-GaN MOS diode, the measured 2DEG density is as high as 2.7 ×1012 cm−2 located at the AlN/GaN hetero-interface. The vertical 2DEG channel with high electron density and mobility can be achieved by depositing AlN (PEALD) layer after trench etch of N-high resistive-N GaN epilayer in the novel structure. The simulations demonstrated that normally off operation can be achieved with a threshold voltage of 2V. Compared with traditional vertical GaN trench MOSFETs, the novel structure can achieved 9 times higher transconductance and extremely high drain current density as high as 9kA/cm2.
{"title":"Novel vertical GaN power devices using PEALD-AlN/GaN heterostructure","authors":"Song Yang, Lei Lei, Kun Yu, Xuhui Wang, Ting Zhou, Xing Lu, Anping Zhang","doi":"10.1109/IFWS.2016.7803765","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803765","url":null,"abstract":"We report on a novel vertical GaN trench structure using PEALD-AlN/GaN hetero-structure for the first time. Through characterizing PEALD-Al2O3/AlN-GaN MOS diode, the measured 2DEG density is as high as 2.7 ×1012 cm−2 located at the AlN/GaN hetero-interface. The vertical 2DEG channel with high electron density and mobility can be achieved by depositing AlN (PEALD) layer after trench etch of N-high resistive-N GaN epilayer in the novel structure. The simulations demonstrated that normally off operation can be achieved with a threshold voltage of 2V. Compared with traditional vertical GaN trench MOSFETs, the novel structure can achieved 9 times higher transconductance and extremely high drain current density as high as 9kA/cm2.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123100458","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803766
Yu Xu, Zongyao Li, Lin Qi, En Zhao, D. Cai, Yumin Zhang, Y. Qiu, Guoqiang Ren, Jicai Zhang, Jianfeng Wang, B. Cao, Ke Xu
Today, heteroepitaxial GaN films on sapphire have focused on conventional two-step growth process using low temperature GaN buffer layer. Here, we show the direct growth of GaN films on sapphire by using a graphene layer at high temperature, which simplified the GaN growth process. The graphene is directly synthesized on non-catalytic sapphire substrate by chemical vapor deposition without problematic transfer processes, using C2H4 as a carbon source at the temperature of 1200 oC. The synthesized graphene has been characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). We have compared the GaN grown on sapphire with and without graphene. The single crystal, smooth surface GaN films has been obtained on sapphire with graphene, and the nucleation of GaN films has been discussed. The GaN films illuminated high near-band-edge emission and good ultraviolet photosensor. It demonstrates that graphene is a potential, useful buffer layer for heteroepitaxy of high quality GaN films.
{"title":"Direct growth of GaN on sapphire with non-catalytic CVD graphene layers at high temperature","authors":"Yu Xu, Zongyao Li, Lin Qi, En Zhao, D. Cai, Yumin Zhang, Y. Qiu, Guoqiang Ren, Jicai Zhang, Jianfeng Wang, B. Cao, Ke Xu","doi":"10.1109/IFWS.2016.7803766","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803766","url":null,"abstract":"Today, heteroepitaxial GaN films on sapphire have focused on conventional two-step growth process using low temperature GaN buffer layer. Here, we show the direct growth of GaN films on sapphire by using a graphene layer at high temperature, which simplified the GaN growth process. The graphene is directly synthesized on non-catalytic sapphire substrate by chemical vapor deposition without problematic transfer processes, using C2H4 as a carbon source at the temperature of 1200 oC. The synthesized graphene has been characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). We have compared the GaN grown on sapphire with and without graphene. The single crystal, smooth surface GaN films has been obtained on sapphire with graphene, and the nucleation of GaN films has been discussed. The GaN films illuminated high near-band-edge emission and good ultraviolet photosensor. It demonstrates that graphene is a potential, useful buffer layer for heteroepitaxy of high quality GaN films.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126630398","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803764
Zijun Chen, Liuan Li, Yue Zheng, Y. Ni, D. Zhou, Liang He, Fan Yang, Lei He, Zhisheng Wu, Baijun Zhang, Yang Liu
The influence of the total thickness (periods of AlN/GaN SLs) of AlN/GaN superlattices (SLs) buffer on the static electrical properties of AlGaN/GaN HFETs is study for the purpose of improving device's breakdown voltage (BV) and reducing its on-resistance (RON). It is found that for top-GaN layer with a constant thickness of lμm, a proper thickness of AlN/GaN SLs buffer (such as 2.5 μm with 100 period AlN/GaN SLs) could obtain better crystal quality of top-GaN layer as well as more robust devices with more superior performance in all aspects. The most robust HFETs in this work have achieved a specific on-resistance (RON, SP) of 0.68 mΩ-cm2 (@ LGD=4μm), a maximum on-state drain current (ID, max) of 430 mA/mm (@ LGD=4μm), an On/Off ratio of 2×108, a BV of 552V at a drain leakage current of lμA/mm (@ LGD=15μm), and a figure-of-merit (FOM=BV2/RON, SP) of 168 MW/cm2 (@ LGD=8μm).
{"title":"Influence of the Aln/Gan superlattices buffer thickness on the electrical properties of Algan/Gan HFET on Si substrate","authors":"Zijun Chen, Liuan Li, Yue Zheng, Y. Ni, D. Zhou, Liang He, Fan Yang, Lei He, Zhisheng Wu, Baijun Zhang, Yang Liu","doi":"10.1109/IFWS.2016.7803764","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803764","url":null,"abstract":"The influence of the total thickness (periods of AlN/GaN SLs) of AlN/GaN superlattices (SLs) buffer on the static electrical properties of AlGaN/GaN HFETs is study for the purpose of improving device's breakdown voltage (BV) and reducing its on-resistance (R<inf>ON</inf>). It is found that for top-GaN layer with a constant thickness of lμm, a proper thickness of AlN/GaN SLs buffer (such as 2.5 μm with 100 period AlN/GaN SLs) could obtain better crystal quality of top-GaN layer as well as more robust devices with more superior performance in all aspects. The most robust HFETs in this work have achieved a specific on-resistance (R<inf>ON, SP</inf>) of 0.68 mΩ-cm<sup>2</sup> (@ L<inf>GD</inf>=4μm), a maximum on-state drain current (I<inf>D, max</inf>) of 430 mA/mm (@ L<inf>GD</inf>=4μm), an On/Off ratio of 2×10<sup>8</sup>, a BV of 552V at a drain leakage current of lμA/mm (@ L<inf>GD</inf>=15μm), and a figure-of-merit (FOM=BV<sup>2</sup>/R<inf>ON, SP</inf>) of 168 MW/cm<sup>2</sup> (@ L<inf>GD</inf>=8μm).","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116308421","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803770
Xiu-bo Liu, Yong-zhi Zhao, Shaodong Wang, Zhi-Qiang Wang
In this paper a novel package based on GaN MMICs chipset, comprising a driver amplifier and a power amplifier using Si-based packing technique will be presented. The GaN HEMT on SiC power amplifiers is superior to GaAs/Si based FET due to its higher power density and wider band gap. The thermal matching and thermal conductivity of the package are taken into consideration in order to avoid the high channel temperature lower the performance of the power amplifier. For an operation frequency band from 14 to 18 GHz, the module achieves beyond 39 dBm of output power under pulsed conditions Vgs = −2 V and Vds = +28 V, small signal gain of around 36.8 dB. The chipset are assembled in a 9.7 mm ×6.5 mm × 0.81 mm Si-based package.
本文提出了一种基于GaN mmic芯片组的新型封装，包括驱动放大器和功率放大器，采用硅基封装技术。SiC功率放大器上的GaN HEMT由于其更高的功率密度和更宽的带隙而优于基于GaAs/Si的FET。为了避免高通道温度降低功率放大器的性能，考虑了封装的热匹配和导热性。在14 ~ 18 GHz的工作频段，在Vgs =−2 V和Vds = +28 V的脉冲条件下，该模块的输出功率超过39 dBm，信号增益约为36.8 dB。芯片组采用9.7 mm ×6.5 mm × 0.81 mm si封装。
{"title":"A novel GaN MMICs packaging using silicon based technology","authors":"Xiu-bo Liu, Yong-zhi Zhao, Shaodong Wang, Zhi-Qiang Wang","doi":"10.1109/IFWS.2016.7803770","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803770","url":null,"abstract":"In this paper a novel package based on GaN MMICs chipset, comprising a driver amplifier and a power amplifier using Si-based packing technique will be presented. The GaN HEMT on SiC power amplifiers is superior to GaAs/Si based FET due to its higher power density and wider band gap. The thermal matching and thermal conductivity of the package are taken into consideration in order to avoid the high channel temperature lower the performance of the power amplifier. For an operation frequency band from 14 to 18 GHz, the module achieves beyond 39 dBm of output power under pulsed conditions Vgs = −2 V and Vds = +28 V, small signal gain of around 36.8 dB. The chipset are assembled in a 9.7 mm ×6.5 mm × 0.81 mm Si-based package.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121443027","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803747
Xuejian Xie, Yan Peng, Xianglong Yang, Xiufang Chen, Xiaobo Hu, Xiangang Xu, Peng Yu, Ruiqi Wang
We have measured the slit width dependence of the linewidth of the first-order Raman lines in 4H-SiC at room temperature. The Raman spectra were fitted into Voigt profile. The Raman linewidth monotonously increased with the slit width, which indicated that the obtained linewidth contained the contribution of instrumental bandpass. To exclude the contribution of instrumental bandpass and get the accurate data for linewidth, a mathematical method was used to eliminate the instrumental bandpass due to the finite slit width. Then the Raman linewidth at zero-slit width was employed to calculate the phonon lifetime by energy-time uncertainty relation. Results showed that for undoped 4H-SiC, the phonon lifetime was in the sequence of E2(TA) > E2(TO) > A1(LO). In addition, the impurity content effect on phonon lifetime was discussed. Results showed that phonon lifetime was shortened with increasing impurity content. However, it was found that the phonon lifetime of E2(TA) mode was more sensitive to impurity content than that of E2(TO) mode.
{"title":"Raman analysis of phonon lifetimes in 4H-SiC and their doping dependence","authors":"Xuejian Xie, Yan Peng, Xianglong Yang, Xiufang Chen, Xiaobo Hu, Xiangang Xu, Peng Yu, Ruiqi Wang","doi":"10.1109/IFWS.2016.7803747","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803747","url":null,"abstract":"We have measured the slit width dependence of the linewidth of the first-order Raman lines in 4H-SiC at room temperature. The Raman spectra were fitted into Voigt profile. The Raman linewidth monotonously increased with the slit width, which indicated that the obtained linewidth contained the contribution of instrumental bandpass. To exclude the contribution of instrumental bandpass and get the accurate data for linewidth, a mathematical method was used to eliminate the instrumental bandpass due to the finite slit width. Then the Raman linewidth at zero-slit width was employed to calculate the phonon lifetime by energy-time uncertainty relation. Results showed that for undoped 4H-SiC, the phonon lifetime was in the sequence of E2(TA) > E2(TO) > A1(LO). In addition, the impurity content effect on phonon lifetime was discussed. Results showed that phonon lifetime was shortened with increasing impurity content. However, it was found that the phonon lifetime of E2(TA) mode was more sensitive to impurity content than that of E2(TO) mode.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134319181","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}
The performance of scaled AlGaN/GaN HFETs was significantly improved by using gate-recess technology and regrown n+-GaN Ohmic contacts. Source-to-drain distance (Zsd) was scaled to 600 nm by employing regrown n+-GaN Ohmic contacts. Low-damage gate recess was taken before 60 nm T-shaped gate metallization. The drain current curve becomes flat over knee voltage, and the short-channel effects were suppressed obviously after gate recessing. The peak transconductance (gm) increased from 607 mS/mm to 764 mS/mm. Moreover, after gate recessing, the value of maximum oscillation frequency (fmax) increases from 192 GHz to 263 GHz, while there is almost no decrease in the value of unity current gain cut-off frequency (fT). The devices with gate recess exhibit a record-high value of √fT·fmax in AlGaN/GaN HFETs. This indicates that the AlGaN/GaNHFETs still have the potential for D-band application with further optimization.
{"title":"Improved performance of scaled AlGaN/GaN HFETs by recessed gate","authors":"Y. Lv, Xubo Song, Zhirong Zhang, X. Tan, Yulong Fang, Zhihong Feng","doi":"10.1109/IFWS.2016.7803769","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803769","url":null,"abstract":"The performance of scaled AlGaN/GaN HFETs was significantly improved by using gate-recess technology and regrown n<sup>+</sup>-GaN Ohmic contacts. Source-to-drain distance (Z<inf>sd</inf>) was scaled to 600 nm by employing regrown n<sup>+</sup>-GaN Ohmic contacts. Low-damage gate recess was taken before 60 nm T-shaped gate metallization. The drain current curve becomes flat over knee voltage, and the short-channel effects were suppressed obviously after gate recessing. The peak transconductance (g<inf>m</inf>) increased from 607 mS/mm to 764 mS/mm. Moreover, after gate recessing, the value of maximum oscillation frequency (f<inf>max</inf>) increases from 192 GHz to 263 GHz, while there is almost no decrease in the value of unity current gain cut-off frequency (f<inf>T</inf>). The devices with gate recess exhibit a record-high value of √f<inf>T</inf>·f<inf>max</inf> in AlGaN/GaN HFETs. This indicates that the AlGaN/GaNHFETs still have the potential for D-band application with further optimization.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121268261","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803753
Zhaoyang Peng, Huajun Shen, Hong Chen, Y. Bai, Yidan Tang, Yiyu Wang, Ximing Chen, Chengzhan Li, Kean Liu, Xinyu Liu
The fabrication of 1200V SiC MOSFET with developed nitrided gate oxide and self-aligned channel technology are reported. Post-oxidation annealing in nitrogen-contained ambient can effectively passivate defects at the SiC/SiO2 interface which is beneficial for the mobility improvement in SiC MOSFETs. The process of nitridation begins from the conduction band and extends to the mid-band-gap gradually. Our newly developed self-aligned channel technology, where side wall and poly-silicon are used as mask instead of traditional metal mask, is efficient in shortening the MOSFET channel to half micro, which helps reduce the channel length of the device. With these two technologies mentioned above, 1200V SiC MOSFET is fabricated based on our own process line. And the current capability increases markedly after gate oxide nitridation and self-aligned channel treatment.
采用氮化栅氧化物和自对准沟道技术制备了1200V SiC MOSFET。含氮环境下的后氧化退火能有效钝化SiC/SiO2界面缺陷，有利于SiC mosfet迁移率的提高。氮化过程从导带开始，逐渐延伸到中带隙。我们新开发的自对准通道技术，使用侧壁和多晶硅作为掩膜而不是传统的金属掩膜，有效地将MOSFET通道缩短到半微，这有助于减少器件的通道长度。利用上述两种技术，基于我们自己的工艺线制造了1200V SiC MOSFET。经栅氧化氮化和自对准沟道处理后，电流性能显著提高。
{"title":"R&D of 1200V SiC MOSFETs with nitrided gate oxide and self-aligned channel technology","authors":"Zhaoyang Peng, Huajun Shen, Hong Chen, Y. Bai, Yidan Tang, Yiyu Wang, Ximing Chen, Chengzhan Li, Kean Liu, Xinyu Liu","doi":"10.1109/IFWS.2016.7803753","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803753","url":null,"abstract":"The fabrication of 1200V SiC MOSFET with developed nitrided gate oxide and self-aligned channel technology are reported. Post-oxidation annealing in nitrogen-contained ambient can effectively passivate defects at the SiC/SiO2 interface which is beneficial for the mobility improvement in SiC MOSFETs. The process of nitridation begins from the conduction band and extends to the mid-band-gap gradually. Our newly developed self-aligned channel technology, where side wall and poly-silicon are used as mask instead of traditional metal mask, is efficient in shortening the MOSFET channel to half micro, which helps reduce the channel length of the device. With these two technologies mentioned above, 1200V SiC MOSFET is fabricated based on our own process line. And the current capability increases markedly after gate oxide nitridation and self-aligned channel treatment.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"16 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123577285","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803755
Fusheng Zhang, Xiufang Chen, Cancan Yu, Li Sun, Xiangang Xu, Xiaobo Hu, Tian Li, Xian Zhao, Yong Zhang, Ruiqi Wang
Large-area uniform monolayer epitaxial graphene (EG) was prepared by the thermal decomposition of 4H-SiC in optimized temperature field. With the increase of substrate diameter, the radial temperature fluctuation also becomes more drastic. The convex and flat temperature fields with different growth system configurations were obtained by VR-PVT software. The EG surface morphology was characterized by atomic force microscopy (AFM). The graphene thickness uniformity was identified by Raman spectroscopy and scanning Kelvin probe microscopy (SKPM). After graphitization in convex temperature field with large axial and radial temperature gradients, the layer of graphene near the edge of the sample was about 1–2 layers thicker than that near the center. At the same time, many messy small steps splitting from big steps reduced the uniformity. By optimizing the temperature filed distribution the ratio of monolayer epitaxial graphene coverage increased from 65% to 94%. Furthermore, growth temperature dependence of the EG layer number and uniformity was investigated. The statistic results indicated that 1700°C was the most suitable growth temperature fabricating high quality and uniformity of EG.
{"title":"Large-area uniform epitaxial graphene on SiC by optimizing temperature field","authors":"Fusheng Zhang, Xiufang Chen, Cancan Yu, Li Sun, Xiangang Xu, Xiaobo Hu, Tian Li, Xian Zhao, Yong Zhang, Ruiqi Wang","doi":"10.1109/IFWS.2016.7803755","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803755","url":null,"abstract":"Large-area uniform monolayer epitaxial graphene (EG) was prepared by the thermal decomposition of 4H-SiC in optimized temperature field. With the increase of substrate diameter, the radial temperature fluctuation also becomes more drastic. The convex and flat temperature fields with different growth system configurations were obtained by VR-PVT software. The EG surface morphology was characterized by atomic force microscopy (AFM). The graphene thickness uniformity was identified by Raman spectroscopy and scanning Kelvin probe microscopy (SKPM). After graphitization in convex temperature field with large axial and radial temperature gradients, the layer of graphene near the edge of the sample was about 1–2 layers thicker than that near the center. At the same time, many messy small steps splitting from big steps reduced the uniformity. By optimizing the temperature filed distribution the ratio of monolayer epitaxial graphene coverage increased from 65% to 94%. Furthermore, growth temperature dependence of the EG layer number and uniformity was investigated. The statistic results indicated that 1700°C was the most suitable growth temperature fabricating high quality and uniformity of EG.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125527703","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803757
Mingsheng Xu, Yuanhang Weng, Hong Wang
The leakage current of buffer layer deteriorates the electronic properties of GaN-based high-electron mobility transistor (HEMT). We proposed a GaN:C/GaN superlattice to improve the resistivity of buffer layer without reducing its crystallization. The leakage current of HEMT with GaN:C/GaN superlattices reduces one order of magnitude compared to the conventional HEMT with carbon-doped buffer.
{"title":"Reduction of leakage current in GaN-based high-electron mobility transistor employing carbon-doped GaN superlattice buffer layers","authors":"Mingsheng Xu, Yuanhang Weng, Hong Wang","doi":"10.1109/IFWS.2016.7803757","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803757","url":null,"abstract":"The leakage current of buffer layer deteriorates the electronic properties of GaN-based high-electron mobility transistor (HEMT). We proposed a GaN:C/GaN superlattice to improve the resistivity of buffer layer without reducing its crystallization. The leakage current of HEMT with GaN:C/GaN superlattices reduces one order of magnitude compared to the conventional HEMT with carbon-doped buffer.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121073319","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 : 2016-11-01DOI: 10.1109/IFWS.2016.7803773
Shuai Yang, Yun Zhang, Lili Sun, Lian Zhang, Zhe Cheng, Junxi Wang, Jinmin Li
In this paper, we study the device physics and device structure design for hybrid bulk acoustic wave resonator (hybrid resonator), which is a new type bulk acoustic resonator formed by the combination of traditional film bulk acoustic wave resonator (FBAR) and solidly mounted resonator (SMR) device structure by Mason model. The simulation results indicate that, compared with temperature-compensated FBAR (TC-FBAR), the input impedance ratio (Ra/Rr) is increased by 120%, and the effective electromechanical coefficient (Kt2) is improved by 45%. Moreover, we study the impact of number of metal/SiO2 Bragg reflectors on the performance of hybrid resonators, and find that hybrid resonator with single Bragg reflector exhibits the best performance. Our simulation results indicate that AlN-based hybrid resonator is very promising for the design of high frequency filters, oscillators and sensors with low temperature coefficient of frequency.
{"title":"Study on AIN-based hybrid bulk acoustic wave resonator with low temperature coefficient of frequency","authors":"Shuai Yang, Yun Zhang, Lili Sun, Lian Zhang, Zhe Cheng, Junxi Wang, Jinmin Li","doi":"10.1109/IFWS.2016.7803773","DOIUrl":"https://doi.org/10.1109/IFWS.2016.7803773","url":null,"abstract":"In this paper, we study the device physics and device structure design for hybrid bulk acoustic wave resonator (hybrid resonator), which is a new type bulk acoustic resonator formed by the combination of traditional film bulk acoustic wave resonator (FBAR) and solidly mounted resonator (SMR) device structure by Mason model. The simulation results indicate that, compared with temperature-compensated FBAR (TC-FBAR), the input impedance ratio (Ra/Rr) is increased by 120%, and the effective electromechanical coefficient (Kt2) is improved by 45%. Moreover, we study the impact of number of metal/SiO2 Bragg reflectors on the performance of hybrid resonators, and find that hybrid resonator with single Bragg reflector exhibits the best performance. Our simulation results indicate that AlN-based hybrid resonator is very promising for the design of high frequency filters, oscillators and sensors with low temperature coefficient of frequency.","PeriodicalId":331453,"journal":{"name":"2016 13th China International Forum on Solid State Lighting: International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS)","volume":"298 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123049884","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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