• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Dual-wavelength ultraviolet photodetector based on vertical(Al,Ga)N nanowires and graphene*

    2021-07-30 07:43:38MinZhou周敏YukunZhao趙宇坤LifengBian邊歷峰JianyaZhang張建亞WenxianYang楊文獻YuanyuanWu吳淵淵ZhiweiXing邢志偉MinJiang蔣敏andShulongLu陸書龍
    Chinese Physics B 2021年7期
    關(guān)鍵詞:周敏趙宇文獻

    Min Zhou(周敏) Yukun Zhao(趙宇坤) Lifeng Bian(邊歷峰) Jianya Zhang(張建亞) Wenxian Yang(楊文獻)Yuanyuan Wu(吳淵淵) Zhiwei Xing(邢志偉) Min Jiang(蔣敏) and Shulong Lu(陸書龍)

    1Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO),Chinese Academy of Sciences(CAS),Suzhou 215123,China

    2School of Nano-Tech and Nano-Bionics,University of Science and Technology of China,Hefei 230026,China

    Keywords: dual-wavelength ultraviolet photodetector,(Al,Ga)N nanowire,graphene,molecular beam epitaxy

    1. Introduction

    In recent years, due to a wide range of applications in communication, flame sensors, ozone monitoring, and even ultraviolet (UV) astronomy, people have great interest in UV-A (320 nm-400 nm) and UV-C (200 nm-280 nm) photodetectors.[1,2]By reducing false positive detection, dual-wavelength photodetectors are beneficial to increase accuracy.[3]In general, measuring dual-wavelength bands typically requires double detectors with separate cooling assemblies and readout circuits.[3,4]However,it could increase the manufacturing costs and enhance the difficulties of assembling double different detectors.[3,5]A single photodetector responding in dual wavelengths paves an efficient way to overcome the above problems.[3]For example, dualwavelength detection can clearly distinguish the missile from its plume and can reduce mine detection errors.[3]Hence,dualwavelength (UV-A/UV-C) photodetectors are necessary and promising for future markets of UV detections.

    Due to the continuous adjustable bandgap covering the range from about 200 nm to 365 nm,(Al,Ga)N can shield the interference of visible light without any special filters compared with Si.[6-10]Thus, (Al,Ga)N is beneficial for detector miniaturization and saving the cost of filters. In addition to the extraordinary characteristics of being nontoxic, long lifetime and high stability against UV radiation, (Al,Ga)N is an ideal material for making UV photodetectors.[6-9,11]Moreover, compared with thin films or bulk, nanowires show better photoelectric properties due to its large specific surface area and smaller size.[12-14]Nanowires have special ability for selectively enhancing nanoscale light absorption due to their optical properties.[15]However, to date, most UV detectors are based on thin films or bulk materials, and few groups have studied UV detectors based on vertical(Al,Ga)N nanowires.[16,17]In our previous work,a UV detector based on(Al,Ga)N nanowires only achieved a single response in the UV range.[16]The results agree with those from another group.[17]The underlying mechanism is still unclear. Therefore, it is promising but highly challenging to achieve dual-wavelength UV photodetectors based on vertical(Al,Ga)N nanowires.

    In this work, we demonstrate a dual-wavelength (UVA/UV-C) detector based on (Al,Ga)N/GaN nanowires. The dual-wavelength detector provides double responses in UVA and UV-C regions. The maximum responsivity of UV-C band is over 15.5 mA·W-1, while that of UV-A band is over 5.0 mA·W-1. Due to the good transparency and conductivity,graphene is utilized as a current collecting layer. The underlying mechanism contributing to the double responses has been studied systematically.

    2. Experiments

    Vertical(Al,Ga)N nanowires were grown on Si substrate by molecular beam epitaxy(MBE).Prior to the MBE growth,the Si(111)substrate in the growth chamber should be heated up to about 900°C for 15 min to eliminate the native oxides.The 7×7 reconstruction was normally observed after this treatment,indicative of a clean surface.Initially,an AlN buffer layer was grown with a nominal Al flux of~3.0 nm·min-1for 1.0 min. Subsequently,GaN nanowires were grown with a Ga flux of~3.0×10-8Torr for about 100 min with a growth rate of~3.8 nm·min-1. The substrate temperature is set to be 770°C.The deposited GaN initially forms into islands which act as a material collector and a seed for the nanowires.[16]After the growth of GaN section,the(Al,Ga)N section was grown for 90 min with a constant substrate temperature of 770°C.Two thin AlN sections were inset into the(Al,Ga)N section as mark layers. When start and finish growing the(Al,Ga)N segment,the shutters of Al and Ga cells were opened and closed simultaneously by the software. To increase the nanowire uniformity,samples were rotated with a rate of 120°/s during the growth process.

    To fabricate the photodetectors,a thick SiO2film was deposited on the surface of nanowires. Then some parts of the SiO2film were removed to form a square area to expose some nanowires. After that, Ti/Al (50/200 nm) was deposited as a backside electrode on the backside of the Si substrate by electron beam evaporation. Ohmic contact is formed by annealing at 400°C in N2atmosphere for 30 min. Graphene was transferred to the top of the nanowires by wet transfer as a transparent current collecting layer.[18]The transfer process is shown in Fig. SI (supporting information). Finally, Ti/Pt/Au(25/55/300 nm) was deposited on the graphene surface as an electrode.

    Scanning electron microscopy(SEM),scanning transmission electron microscopy(STEM)and high-resolution energy dispersive x-ray (EDX) mapping were used to characterize the surface morphology and element distribution of nanowires.The STEM samples were prepared by focused ion beam(FIB).The intrinsic emission spectra of (Al,Ga)N nanowires were measured by photoluminescence (PL). The current-voltage and transient responses characteristics of the (Al,Ga)N photodetectors were measured by the probe station. The spectral response measurement employed a self-constructed photoelectric measurement system mainly consisting of an optical chopper, a xenon lamp, a data processing center and a power supply.

    3. Results and discussion

    From the top-view and side-view SEM images in Fig. 1(a), the vertical nanowires are formed and distributed on the Si substrate with good verticality and small fluctuation.As shown in Fig. 1(b), vertical (Al,Ga)N sections have been fabricated as designed. The lateral surface of GaN segment is wrapped by (Al,Ga)N section, forming a core-shell structure. Fig. 1(c) illustrates element distribution from the top to bottom regions of a nanowire,which further demonstrates the existence of(Al,Ga)N section.

    Fig. 1. (a) SEM images of vertical (Al,Ga)N nanowires. (b) High angle annular dark field STEM images of vertical(Al,Ga)N nanowires. (c)Highresolution EDX mapping analysis about the element distributions of vertical(Al,Ga)N nanowires.

    The PL spectra of (Al, Ga)N nanowires are shown in Fig. 2(a).Eg(AlN) andEg(GaN) are the bandgap of AlN and GaN at room temperature, which are 6.2 eV and 3.4 eV,respectively,[19,20]

    According to Eq.(1),the Al content is calculated to be about 18%.[21]As the Raman spectrum shown in Fig.2(b),three obvious peaks exist, namely D peak, G peak and 2D peak. G peak(~1581 cm-1)is caused by the in-plane vibration of sp2hybrid carbon atoms,which proves the existence of graphene after fabricating detectors.[16]D peak (~1343 cm-1) is related to graphene defects[22]and the 2D peak(~2693 cm-1)in graphene is due to two phonons resonance.[23]The number of graphene layers is reflected by the ratio of 2D peak intensity to G peak intensity(I2D/IG).By calculating,the ratioI2D/IGis 0.56,indicating that graphene has a multilayer structure.[24,25]TheI-Vcharacteristics of the detector under dark,UV-A and UV-C illumination (at 254 nm and 365 nm, corresponding to AlGaN and GaN band edge, respectively) were measured by Agilent B1505A instrument for observing the rectification and photo response characteristics. As shown in Fig. 2(c), theIVcurves of the detector under no illumination are nonlinear,which indicates that Schottky contact exists between graphene and nanowires.[26]In addition,under 254 nm and 365 nm illumination, the asymmetry is more obvious relative to the bias direction,indicating that the detector has good response characteristics to UV-C and UV-A illumination. Furthermore,the dark current of the detector is 34.6 nA at-2 V with an area of 0.96 mm2.

    Fig. 2. (a) PL spectrum of vertical (Al, Ga)N nanowire array. (b) Raman spectrum of the graphene film measured with an excitation wavelength of 532 nm. (c) Current-voltage characteristics of detector in dark, UV-A and UV-C illumination measured at room temperature.

    Figure 3(a)shows a schematic diagram of the detector under the measurement of responsiveness. When testing responsiveness,a bias of-2 V is applied to the detector.The spectral responsivity of the detector is defined as the photocurrent output under the action of the unit incident radiation power.[27]As shown in Fig. 3(b), the black triangle represents the experimental data,and the red line represents the data smoothed by 12 points. It is clearly illustrated that the detector shows a dual-wavelength response in the band of 240 nm-400 nm.The maximum responsivity of the first response in the range of UV-C band exceeds 15.5 mA·W-1, while that of the second response in the range of UV-A band is over 5.0 mA·W-1.The rejection ratio (R254nm/R450nm) exceeds 35 times at an applied bias of-2 V.

    Fig.3. (a)Schematic diagram of detector. (b)Spectral response of the detector at the bias at-2 V.

    Fig.4. (a)Transient response of the detector to 254 nm(UV-C)illumination.(b)Transient response of the detector to 365 nm(UV-A)illumination.

    Figures 4(a) and 4(b) show the current switching characteristics of the detector under UV-C (254 nm) and UV-A(365 nm)illumination at-2 V,corresponding to the first and the second responses,respectively. The on/off current can increase/decrease in a certain period of time with/without UV irradiation. All measurements have been conducted at room temperature in air. The rise time (defined as the time when the current rises from 10%to 90%of the peak current value)is less than 20 ms and 20 ms and the decay time (defined as the time when the current drops from 90% to 10% of the peak current value) is less than 960 ms and 955 ms under 254 nm and 365 nm illumination, respectively. The accuracy of our equipment is 20 ms. By comparing the key parameters listed in Table 1, graphene/AlGaN /GaN nanowires has advantages in transient response compared with some recent new photodetectors.[28-33]

    Table 1. Comparison of response time between this work and some state-of-the-art reports.

    In order to further study the underlying mechanism of dual-wavelength UV detector,we plot the schematic diagrams in Fig.5. At-2 V bias voltage, when UV light irradiates on the photodetector(Fig.5(a)),photons can reach the nanowires through the graphene as it is thin enough and transparent in the UV range. Then, photons can be absorbed by (Al,Ga)N and GaN sections, producing electron-hole pairs. Due to the core-shell structure of nanowires,there are two ways(Fig.5(a)1 and 2) for photogenerated carriers to diffuse to the electrodes. “1” in Fig. 5(a) indicates the common way, and carriers are diffused along the vertical direction to both sides of the nanowires. The other way (“2” in Fig. 5(a)) is utilized for carriers to diffuse along shell walls, which paves an addition way for the carrier transports. Therefore, electrons are easier to be collected, contributing to the fast response speed(Table 1). Figure 5(b) shows the schematic of energy band of(Al,Ga)N nanowires in this work,while Figs.5(c)and 5(d)are corresponding to the(Al,Ga)N nanowires from Refs.[17]and[16], respectively. As illustrated in Fig.5(b), due to AlN sections are very thin, it is easy for the photogenerated carriers to pass through by diffusion or tunneling. Therefore, the photogenerated electrons within the(Al,Ga)N section can also pass through the GaN layer and be collected by the electrode.

    Although the (Al,Ga)N nanowires from Ref. [17] has GaN section, the responsivity does not have an obvious peak corresponding to GaN (Fig. 5(c) from Ref. [17]). It is proposed that the main reason is the ratio of the thicknesses of(Al,Ga)N and GaN sections as shown below:HereTis defined as the thickness. Theηin Ref.[17]is equal to 3, which is much larger than thatη(~0.61) in this work.Thus,compared to that in Fig.5(b),the smaller proportion of holes generated within the GaN section (Fig. 5(c)) can cross the(Al,Ga)N layer and then be collected by the electrode. In addition,although theη(~0.29)in Ref.[16]is smaller than that in this work, we still cannot achieve the obvious dualwavelength responses (Fig. 5(d) from Ref. [16]). According to the PL spectra in Fig.2(a)and Ref.[16],as well as Eqs.(1)and(3),the composition of Al in Ref.[16]is calculated to be about 6.5%, which is much smaller than that(~18%)in this work. When the Al composition is very low, the band gap of (Al,Ga)N section is pretty close to GaN. In other words,when the difference (ΔEg) of the energy bands of (Al,Ga)N and GaN sections is very small, it should be difficult to separate the responses of (Al,Ga)N and GaN sections to achieve dual-wavelength responses. As a result, bothηand ΔEgare the key parameters to achieve dual-wavelength UV responses.

    Fig. 5. (a) Schematic diagram of UV irradiation on the photodetector. Enlarged image indicates the diffusion of photogenerated carriers within the core-shell structure. (b)Energy band diagram of the(Al,Ga)N nanowires under UV illumination in this work. (c)Energy band diagram of the(Al,Ga)N nanowires from Ref. [17]. (d) Energy band diagram of the (Al,Ga)N nanowires from Ref.[16].

    4. Conclusion

    In summary, we demonstrate a dual-wavelength (UVA/UV-C) photodetector based on vertical (Al,Ga)N/GaN nanowires grown by MBE. The current switching characteristics of the detector indicates a good repeatability. Moreover, due to the systematic analysis, the ratio of the thicknesses and the energy band difference of (Al,Ga)N and GaN sections could be the main parameters contributing to the dualwavelength response. By using the transparent graphene, the maximum responsivity of UV-C band is over 15.5 mA·W-1,and the rejection ratio exceeds 35 times at an applied bias of-2 V. This work is pretty promising for promoting the development of dual-wavelength UV detectors for wide applications.

    猜你喜歡
    周敏趙宇文獻
    極值點偏移問題的破解策略
    例談三角函數(shù)問題求解中的易錯點
    Hostile takeovers in China and Japan
    速讀·下旬(2021年11期)2021-10-12 01:10:43
    周敏德藏石欣賞
    寶藏(2020年6期)2020-10-15 15:37:54
    伴你闖蕩是愛,放你獨處也是愛
    37°女人(2019年12期)2019-12-19 06:09:11
    Cultural and Religious Context of the Two Ancient Egyptian Stelae An Opening Paragraph
    大東方(2019年12期)2019-10-20 13:12:49
    The Application of the Situational Teaching Method in English Classroom Teaching at Vocational Colleges
    The Role and Significant of Professional Ethics in Accounting and Auditing
    商情(2017年1期)2017-03-22 16:56:36
    你愿意為我而死嗎
    喜劇世界(2016年1期)2016-12-06 18:56:20
    動 靜(短篇小說)
    欧美日韩视频高清一区二区三区二| 国产伦理片在线播放av一区| 午夜免费鲁丝| 欧美亚洲 丝袜 人妻 在线| 精品少妇黑人巨大在线播放| 51国产日韩欧美| 少妇的逼好多水| 成人黄色视频免费在线看| av福利片在线观看| a级一级毛片免费在线观看| 亚洲精品日本国产第一区| 男女边吃奶边做爰视频| 亚洲熟女精品中文字幕| 性高湖久久久久久久久免费观看| 国产精品99久久99久久久不卡 | 亚洲av成人精品一区久久| 欧美成人a在线观看| 国产成人91sexporn| 久久久久久久久久久免费av| 午夜精品国产一区二区电影| 国语对白做爰xxxⅹ性视频网站| 国产毛片在线视频| 国产一级毛片在线| 精品少妇久久久久久888优播| 国产有黄有色有爽视频| av在线老鸭窝| 国产免费一区二区三区四区乱码| 国内少妇人妻偷人精品xxx网站| 成年女人在线观看亚洲视频| 久久精品久久久久久久性| 黄色怎么调成土黄色| 久久青草综合色| 少妇的逼好多水| 国产成人免费观看mmmm| 国产爱豆传媒在线观看| 在线看a的网站| 中国美白少妇内射xxxbb| 欧美xxxx黑人xx丫x性爽| 亚洲自偷自拍三级| 亚洲精品aⅴ在线观看| 国产精品久久久久久久久免| av国产久精品久网站免费入址| 一级片'在线观看视频| 欧美精品一区二区免费开放| 亚洲中文av在线| 国产一区有黄有色的免费视频| 秋霞在线观看毛片| 日韩成人av中文字幕在线观看| 久久99热这里只有精品18| 日韩欧美 国产精品| 99久久精品一区二区三区| 国产乱来视频区| 精品少妇久久久久久888优播| 国产精品秋霞免费鲁丝片| 成人毛片a级毛片在线播放| 日韩,欧美,国产一区二区三区| 国产 一区 欧美 日韩| 欧美精品亚洲一区二区| 久久韩国三级中文字幕| 国国产精品蜜臀av免费| 五月伊人婷婷丁香| 成人毛片a级毛片在线播放| 成人免费观看视频高清| 国产在线男女| 九九爱精品视频在线观看| 国产中年淑女户外野战色| 男人爽女人下面视频在线观看| 亚洲色图综合在线观看| 五月玫瑰六月丁香| 日韩不卡一区二区三区视频在线| 成人毛片a级毛片在线播放| 国产欧美亚洲国产| 欧美变态另类bdsm刘玥| 极品教师在线视频| 国产综合精华液| 久久精品国产自在天天线| 日韩国内少妇激情av| h视频一区二区三区| 久久青草综合色| 寂寞人妻少妇视频99o| 免费看光身美女| 免费黄网站久久成人精品| av不卡在线播放| 大片免费播放器 马上看| 亚洲国产欧美在线一区| 我的老师免费观看完整版| 久久毛片免费看一区二区三区| 干丝袜人妻中文字幕| 亚洲婷婷狠狠爱综合网| 国产精品欧美亚洲77777| 国产极品天堂在线| 精品酒店卫生间| 精品人妻一区二区三区麻豆| 精品人妻熟女av久视频| 黄色视频在线播放观看不卡| 久久久色成人| 18禁在线无遮挡免费观看视频| 精品一区在线观看国产| 深爱激情五月婷婷| 国产亚洲91精品色在线| 国产精品久久久久久久电影| 久久97久久精品| 七月丁香在线播放| 亚洲精品,欧美精品| 日韩av不卡免费在线播放| 亚洲第一区二区三区不卡| 亚洲最大成人中文| 在线观看免费视频网站a站| 中文字幕制服av| 少妇熟女欧美另类| 亚洲高清免费不卡视频| 国产亚洲最大av| 欧美日韩精品成人综合77777| 午夜福利网站1000一区二区三区| 欧美人与善性xxx| tube8黄色片| 在现免费观看毛片| 国产免费视频播放在线视频| 高清日韩中文字幕在线| 亚洲精品aⅴ在线观看| 成人综合一区亚洲| 妹子高潮喷水视频| 秋霞在线观看毛片| 日日摸夜夜添夜夜爱| 午夜福利视频精品| 大片免费播放器 马上看| 亚洲高清免费不卡视频| 亚洲精品久久午夜乱码| 女人十人毛片免费观看3o分钟| 国产免费一区二区三区四区乱码| 午夜福利影视在线免费观看| 国产高清有码在线观看视频| av一本久久久久| 日本wwww免费看| 男女边摸边吃奶| 美女脱内裤让男人舔精品视频| 高清视频免费观看一区二区| 亚洲精品一区蜜桃| 一本一本综合久久| 亚洲国产欧美人成| 亚洲真实伦在线观看| 内射极品少妇av片p| 国产精品伦人一区二区| 精品久久久久久久久av| 哪个播放器可以免费观看大片| 在线精品无人区一区二区三 | 婷婷色av中文字幕| 99久国产av精品国产电影| 卡戴珊不雅视频在线播放| 一级片'在线观看视频| 亚洲国产av新网站| 免费人妻精品一区二区三区视频| 高清午夜精品一区二区三区| 免费大片黄手机在线观看| 少妇的逼水好多| 久久精品国产亚洲av天美| 一个人免费看片子| 国产乱人偷精品视频| 亚洲欧美一区二区三区国产| 最近手机中文字幕大全| 黄色怎么调成土黄色| 成人影院久久| 久久久国产一区二区| 97超视频在线观看视频| 免费不卡的大黄色大毛片视频在线观看| 少妇人妻一区二区三区视频| 久久精品人妻少妇| 日本免费在线观看一区| 成人亚洲精品一区在线观看 | 日本欧美视频一区| 亚洲美女搞黄在线观看| 国产视频内射| 晚上一个人看的免费电影| 久久精品久久久久久久性| 欧美精品亚洲一区二区| 最近中文字幕高清免费大全6| 丰满乱子伦码专区| 丰满乱子伦码专区| 国国产精品蜜臀av免费| 亚洲美女搞黄在线观看| 建设人人有责人人尽责人人享有的 | 秋霞伦理黄片| 一级爰片在线观看| 黄色欧美视频在线观看| 乱码一卡2卡4卡精品| 久久精品国产鲁丝片午夜精品| 成年av动漫网址| 女的被弄到高潮叫床怎么办| 中文字幕制服av| 国产深夜福利视频在线观看| 亚洲av成人精品一区久久| 久久久久久久亚洲中文字幕| 国产深夜福利视频在线观看| 日日啪夜夜爽| 黄色欧美视频在线观看| 亚洲人成网站高清观看| videos熟女内射| 欧美成人精品欧美一级黄| 久久久久久久大尺度免费视频| 精品99又大又爽又粗少妇毛片| 久久99热6这里只有精品| 国产 精品1| 国内精品宾馆在线| 2021少妇久久久久久久久久久| 最近手机中文字幕大全| 一区二区三区乱码不卡18| videossex国产| 亚洲欧美一区二区三区国产| 国产乱来视频区| 超碰97精品在线观看| 亚洲精品中文字幕在线视频 | 国产 一区精品| 午夜福利在线在线| 午夜福利高清视频| 亚洲精品久久久久久婷婷小说| 日本-黄色视频高清免费观看| 黄色日韩在线| 成人高潮视频无遮挡免费网站| 亚洲,欧美,日韩| 欧美人与善性xxx| 欧美+日韩+精品| 九草在线视频观看| 女人久久www免费人成看片| 高清视频免费观看一区二区| 久久女婷五月综合色啪小说| 欧美激情极品国产一区二区三区 | 最近中文字幕高清免费大全6| 18禁在线播放成人免费| 国产成人精品婷婷| 亚洲精品,欧美精品| 亚洲av中文av极速乱| h日本视频在线播放| 日本黄色日本黄色录像| 看十八女毛片水多多多| 免费av不卡在线播放| 国产高清不卡午夜福利| 久久热精品热| 欧美精品一区二区免费开放| 亚洲美女黄色视频免费看| 日本午夜av视频| 久久精品久久久久久噜噜老黄| 看非洲黑人一级黄片| 亚洲精品色激情综合| 久久99热这里只频精品6学生| 最近中文字幕高清免费大全6| 亚洲高清免费不卡视频| 久久久色成人| 国产爽快片一区二区三区| 精品亚洲成国产av| 日韩一区二区视频免费看| 国产深夜福利视频在线观看| 亚洲精华国产精华液的使用体验| 国产一区二区三区综合在线观看 | 美女高潮的动态| 人妻少妇偷人精品九色| 久久精品久久久久久久性| 99久久人妻综合| 一个人免费看片子| 久久毛片免费看一区二区三区| 日韩,欧美,国产一区二区三区| 久久国产精品男人的天堂亚洲 | 国精品久久久久久国模美| 日本爱情动作片www.在线观看| 精品久久久久久久末码| 国产中年淑女户外野战色| 国产日韩欧美亚洲二区| 欧美+日韩+精品| 亚洲av日韩在线播放| 日韩精品有码人妻一区| 国产精品久久久久久久电影| 中文天堂在线官网| 国产精品福利在线免费观看| a 毛片基地| 国产老妇伦熟女老妇高清| 人妻少妇偷人精品九色| 97精品久久久久久久久久精品| 欧美3d第一页| 久久99热6这里只有精品| 亚洲图色成人| tube8黄色片| 亚洲人成网站在线观看播放| 国产一区二区三区综合在线观看 | 一本久久精品| 中文字幕精品免费在线观看视频 | 亚洲丝袜综合中文字幕| 嘟嘟电影网在线观看| 97在线人人人人妻| 又黄又爽又刺激的免费视频.| 久久这里有精品视频免费| 亚洲,欧美,日韩| 不卡视频在线观看欧美| 岛国毛片在线播放| 你懂的网址亚洲精品在线观看| www.av在线官网国产| 国产有黄有色有爽视频| 成人亚洲精品一区在线观看 | 99re6热这里在线精品视频| 国产又色又爽无遮挡免| 高清视频免费观看一区二区| 国产有黄有色有爽视频| 欧美日韩视频精品一区| 哪个播放器可以免费观看大片| 久久国产乱子免费精品| 18禁裸乳无遮挡动漫免费视频| 青春草亚洲视频在线观看| 一二三四中文在线观看免费高清| 女性被躁到高潮视频| 极品教师在线视频| 国产午夜精品一二区理论片| 寂寞人妻少妇视频99o| 深夜a级毛片| 一边亲一边摸免费视频| 亚洲精品久久午夜乱码| 性色avwww在线观看| 国产精品国产三级国产专区5o| 久久久久久人妻| 中文字幕久久专区| 亚洲无线观看免费| 国产高清不卡午夜福利| 三级国产精品欧美在线观看| 亚洲精品日韩av片在线观看| 亚洲av福利一区| 人人妻人人添人人爽欧美一区卜 | 亚洲伊人久久精品综合| 男女边吃奶边做爰视频| 欧美成人a在线观看| 97精品久久久久久久久久精品| 欧美高清性xxxxhd video| 日韩欧美一区视频在线观看 | av女优亚洲男人天堂| 日韩 亚洲 欧美在线| 亚洲精品乱码久久久v下载方式| 赤兔流量卡办理| 午夜免费观看性视频| 十八禁网站网址无遮挡 | 毛片女人毛片| 如何舔出高潮| 另类亚洲欧美激情| 午夜福利在线在线| 各种免费的搞黄视频| 夜夜骑夜夜射夜夜干| 欧美3d第一页| 精品久久久噜噜| 黄色一级大片看看| 一级毛片黄色毛片免费观看视频| 免费高清在线观看视频在线观看| 亚洲国产欧美在线一区| 久久久久久久精品精品| 色婷婷久久久亚洲欧美| 久久精品国产a三级三级三级| 99久久精品一区二区三区| 看免费成人av毛片| 亚洲美女黄色视频免费看| 欧美另类一区| 热99国产精品久久久久久7| av线在线观看网站| 国产一区二区三区综合在线观看 | 午夜福利在线在线| 国产伦精品一区二区三区视频9| 91久久精品国产一区二区三区| 热99国产精品久久久久久7| 成年av动漫网址| 国产一区有黄有色的免费视频| 少妇高潮的动态图| 欧美亚洲 丝袜 人妻 在线| 777米奇影视久久| 欧美成人a在线观看| 热re99久久精品国产66热6| 日韩电影二区| 国产有黄有色有爽视频| 黄片wwwwww| 黑人猛操日本美女一级片| 性色avwww在线观看| 女的被弄到高潮叫床怎么办| 欧美变态另类bdsm刘玥| 亚洲第一区二区三区不卡| 亚洲av男天堂| 一级二级三级毛片免费看| 国产人妻一区二区三区在| 精品亚洲成国产av| 波野结衣二区三区在线| 国产精品成人在线| 午夜激情久久久久久久| 欧美日韩国产mv在线观看视频 | 成人午夜精彩视频在线观看| 免费大片黄手机在线观看| 自拍偷自拍亚洲精品老妇| 色哟哟·www| 最近手机中文字幕大全| 亚洲人成网站在线播| 80岁老熟妇乱子伦牲交| 永久网站在线| 十分钟在线观看高清视频www | 一个人免费看片子| 国产成人精品福利久久| 日韩av不卡免费在线播放| 欧美精品国产亚洲| 2021少妇久久久久久久久久久| av在线老鸭窝| 亚洲色图av天堂| av国产免费在线观看| 日韩强制内射视频| 日本欧美国产在线视频| 老女人水多毛片| 一级毛片黄色毛片免费观看视频| 欧美日韩一区二区视频在线观看视频在线| 汤姆久久久久久久影院中文字幕| 精品一区在线观看国产| 美女高潮的动态| 精品一区二区三卡| 日本-黄色视频高清免费观看| 久久99精品国语久久久| 丰满乱子伦码专区| 亚洲国产色片| 成人美女网站在线观看视频| av福利片在线观看| 一区二区av电影网| 一二三四中文在线观看免费高清| 色视频www国产| 日韩电影二区| 亚洲色图av天堂| 又大又黄又爽视频免费| 卡戴珊不雅视频在线播放| 久久久久久久大尺度免费视频| 纵有疾风起免费观看全集完整版| 少妇裸体淫交视频免费看高清| 高清毛片免费看| 日本黄大片高清| 色哟哟·www| 麻豆乱淫一区二区| 亚洲成人av在线免费| 99久久中文字幕三级久久日本| 亚洲精品成人av观看孕妇| 黄色日韩在线| 国产精品一区二区在线不卡| 久久久久久久国产电影| 永久网站在线| 人人妻人人添人人爽欧美一区卜 | 一个人免费看片子| 久久久亚洲精品成人影院| 一区二区三区四区激情视频| 精品视频人人做人人爽| 大话2 男鬼变身卡| 毛片一级片免费看久久久久| 日本欧美视频一区| 亚洲熟女精品中文字幕| 亚洲色图综合在线观看| 午夜精品国产一区二区电影| 亚洲中文av在线| 少妇丰满av| 夫妻午夜视频| 国产视频内射| 99re6热这里在线精品视频| 国产 一区精品| 久久韩国三级中文字幕| 久久久久久久久久久丰满| 成人高潮视频无遮挡免费网站| 午夜福利在线在线| 欧美日韩视频高清一区二区三区二| 蜜桃在线观看..| 国产在线视频一区二区| 日韩精品有码人妻一区| 王馨瑶露胸无遮挡在线观看| 涩涩av久久男人的天堂| 日本-黄色视频高清免费观看| 亚洲av男天堂| 国产片特级美女逼逼视频| 青青草视频在线视频观看| 99久久精品国产国产毛片| 欧美97在线视频| 2022亚洲国产成人精品| 一本色道久久久久久精品综合| 免费观看的影片在线观看| 夜夜爽夜夜爽视频| 国产永久视频网站| 国产精品欧美亚洲77777| 麻豆乱淫一区二区| 久久精品国产亚洲av涩爱| 午夜日本视频在线| 欧美zozozo另类| 国产精品久久久久成人av| 久久精品熟女亚洲av麻豆精品| 交换朋友夫妻互换小说| 色视频在线一区二区三区| 一级爰片在线观看| 欧美bdsm另类| 性色avwww在线观看| 在线观看一区二区三区激情| 成人毛片60女人毛片免费| 亚洲色图综合在线观看| 国产日韩欧美在线精品| 精品久久久久久久久亚洲| 婷婷色综合www| 少妇的逼水好多| 美女主播在线视频| 大片免费播放器 马上看| 日韩视频在线欧美| 亚洲av国产av综合av卡| 少妇裸体淫交视频免费看高清| 亚洲成人一二三区av| 中文资源天堂在线| 午夜福利网站1000一区二区三区| 精品久久久久久久久av| 日韩一区二区三区影片| 九草在线视频观看| 久久久久久久久大av| 男人和女人高潮做爰伦理| 国产av一区二区精品久久 | 国产成人精品一,二区| 国内少妇人妻偷人精品xxx网站| 青春草亚洲视频在线观看| 精品99又大又爽又粗少妇毛片| 日本-黄色视频高清免费观看| 精品久久久久久久久av| 少妇熟女欧美另类| 看免费成人av毛片| 黑人高潮一二区| 国产精品一二三区在线看| 国产男女超爽视频在线观看| 伦理电影免费视频| videos熟女内射| 中文天堂在线官网| 91精品伊人久久大香线蕉| a级一级毛片免费在线观看| 国产一区二区在线观看日韩| 乱系列少妇在线播放| 五月开心婷婷网| av免费在线看不卡| 国产亚洲一区二区精品| 中文字幕av成人在线电影| 一级毛片我不卡| 亚洲欧美中文字幕日韩二区| 国产免费视频播放在线视频| 久久亚洲国产成人精品v| 国产精品爽爽va在线观看网站| av黄色大香蕉| 又大又黄又爽视频免费| 香蕉精品网在线| 两个人的视频大全免费| 一本久久精品| 三级经典国产精品| 国产成人免费无遮挡视频| 国产在线视频一区二区| 丰满迷人的少妇在线观看| 久久精品熟女亚洲av麻豆精品| 色吧在线观看| 国产爽快片一区二区三区| 只有这里有精品99| 久久久久精品性色| 日本免费在线观看一区| 天天躁日日操中文字幕| 欧美人与善性xxx| 国产精品一区二区在线不卡| 亚洲三级黄色毛片| 国产精品国产三级国产av玫瑰| 直男gayav资源| 国内揄拍国产精品人妻在线| 婷婷色av中文字幕| 亚洲一区二区三区欧美精品| 男人和女人高潮做爰伦理| 天堂中文最新版在线下载| 午夜老司机福利剧场| av福利片在线观看| 亚洲欧美日韩卡通动漫| 亚洲,欧美,日韩| 成人18禁高潮啪啪吃奶动态图 | 国产精品不卡视频一区二区| 我要看日韩黄色一级片| 一个人看视频在线观看www免费| 国产精品久久久久久av不卡| 肉色欧美久久久久久久蜜桃| 国产精品一区www在线观看| 亚洲一区二区三区欧美精品| 欧美3d第一页| 欧美日韩视频精品一区| 国产亚洲一区二区精品| av在线观看视频网站免费| 51国产日韩欧美| 男人舔奶头视频| 少妇熟女欧美另类| 国产精品成人在线| 热re99久久精品国产66热6| 欧美日韩视频精品一区| 成年免费大片在线观看| 黄片无遮挡物在线观看| 国产v大片淫在线免费观看| 精品久久久久久久久亚洲| 纯流量卡能插随身wifi吗| 久久精品久久久久久噜噜老黄| 亚洲人成网站在线播| 黄片wwwwww| 国产亚洲av片在线观看秒播厂| 精品午夜福利在线看| 日韩电影二区| 久久久久人妻精品一区果冻| 97超碰精品成人国产| 国产精品女同一区二区软件| 色5月婷婷丁香| 久久精品久久精品一区二区三区| 国产欧美亚洲国产| 大片免费播放器 马上看| av.在线天堂| 最近2019中文字幕mv第一页| 成人黄色视频免费在线看| 国产在线一区二区三区精| 高清日韩中文字幕在线| 99热这里只有是精品50| 亚洲内射少妇av| 国产精品国产av在线观看| 舔av片在线| 内射极品少妇av片p| 91久久精品国产一区二区成人| 三级经典国产精品| 18禁裸乳无遮挡免费网站照片| 插逼视频在线观看|