Facile fabrication of heterostructure with p-BiOCl nanoflakes and n-ZnO thin film for UV photodetectors

Herein, high-quality n-ZnO film layer on c-sapphire and well-crystallized tetragonal p-BiOCl nanoflakes on Cu foil are prepared, respectively. According to the absorption spectra, the bandgaps of n-ZnO and p-BiOCl are confirmed as ~3.3 and~3.5 eV, respectively. Subsequently, a p-BiOCl/n-ZnO heterostructural photodetector is constructed after a facile mechanical bonding and post annealing process. At –5 V bias, the photocurrent of the device under 350 nm irradiation is ~800 times higher than that in dark, which indicates its strong UV light response characteristic. However, the on/off ratio of In–ZnO–In photodetector is ~20 and the Cu–BiOCl–Cu photodetector depicts very weak UV light response. The heterostructure device also shows a short decay time of 0.95 s, which is much shorter than those of the devices fabricated from pure ZnO thin film and BiOCl nanoflakes. The p-BiOCl/n-ZnO heterojunction photodetector provides a promising pathway to multifunctional UV photodetectors with fast response, high signal-to-noise ratio, and high selectivity.

Optical Field Confinement Enhanced Single ZnO Microrod UV Photodetector

ZnO microrods are synthesized using the vapor phase transport method, and the magnetron sputtering is used to decorate the A1 nanoparticles （NPs） on a single ZnO microrod. The micro-PL and I-V responses are measured before and after the decoration orAl NPs. The FDTD stimulation is also carried out to demonstrate the optical field distribution around the decoration of Al NPs on the surface of a ZnO microrod. Due to an implementation of AI NPs, the ZnO microrod exhibits an improved photoresponse behavior. In addition, AI NPs induced localized surface plasmons （LSPs） as well as improved optical field confinement can be ascribed to an enhancement of ultraviolet （UV） response. This research provides a method for improving the responsivity of photodetectors.

The simulation of temperature dependence of responsivity and response time for 6H-SiC UV photodetector

In this paper the temperature dependence of responsivity and response time for 6H-SiC ultraviolet （UV） photodetector is simulated based on numerical model in the range from 300 K to 900 K. The simulation results show that the responsivity and the response time of device are less sensitive to temperature and this kind of UV photodetector has excellent temperature stability. Also the effects of device structure and bias voltage on the responsivity and the response time are presented. The thicker the drift region is, the higher the responsivity and the longer the response time are. So the thickness of drift region has to be carefully designed to make trade-off between responsivity and response time.

High-performance self-powered GaN/PEDOT:PSS hybrid heterojunction UV photodetector for optical communication

Self-powered ultraviolet photodetectors(UVPDs)provide great possibility for the next-generation energy conservation optical communication technology;while the high photodetection performance at zero bias is still a tremendous challenge.Herein,ntype GaN film with Si-doping concentration of~1018cm^(-3)and p-type organic PEDOT:PSS were adopted to construct a planar hybrid heterojunction via the simple spin-coating method.Profited from typical type-Ⅱenergy band alignment and giant photovoltaic effect at GaN/PEDOT:PSS inorganic-organic interface,the fabricated UVPD achieved excellent self-powered photoelectrical properties in dual-band with large R of 0.96 A/W(2.8 A/W),superior D*of 5.7×1012Jones(1.7×10^(13)Jones),prominent EQE of 325%(1371%),high on/off ratio of 9.65×10^(3)(6.15×10^(3))and fast rise/decay time of 60.7/124.5 ms(30.9/26.7 ms)for UVA(UVC)band,as well as outstanding UV/visible rejection ratio and great detection repeatability.Functioned as an optical signal receiver,this designed self-powered UVPD decoded a message of“NJUPT”from a simple optical communication system.These results open a new avenue for GaN/PEDOT:PSS heterojunction in UV communications and related applications.

Integration of filter membrane and Ca_(2)Nb_(3)O_(10) nanosheets for high performance flexible UV photodetectors

We report that the integration of filter membrane and Ca_(2)Nb_(3)O_(10)nanosheets(FM@CNO) UV photodetector(UV PD) shows high performance and excellent flexibility. The Ca_(2)Nb_(3)O_(10)nanosheets were prepared by a facile solid-state reaction and liquid exfoliation process. The Ca_(2)Nb_(3)O_(10)nanosheets can be integrated into the pores of a filter membrane via a simple vacuum filtration method. The FM@CNO UV PD shows high performance under 300 nm light illumination at 5 V bias, including high responsivity(0.08 AW^(-1)), high detectivity(1.1 × 10^(12)Jones), high UV/visible rejection ratio(3.86 × 10^(3)) and fast speed(0.12/1.24 ms). Furthermore, the FM@CNO device exhibits excellent flexibility after many bending cycles.In addition, the FM@CNO array device was used as a pixel array detector for UV imaging. This work provides a novel approach to achieve high performance flexible PDs based on filter membrane and two dimensional materials.

ZnO nanowires based degradable high-performance photodetectors for eco-friendly green electronics

Disposable devices designed for single and/or multiple reliable measurements over a short duration have attracted considerable interest recently. However, these devices often use non-recyclable and non-biodegradable materials and wasteful fabrication methods. Herein, we present ZnO nanowires(NWs) based degradable high-performance UV photodetectors(PDs) on flexible chitosan substrate. Systematic investigations reveal the presented device exhibits excellent photo response, including high responsivity(55 A/W), superior specific detectivity(4×10^(14) jones), and the highest gain(8.5×10~(10)) among the reported state of the art biodegradable PDs. Further, the presented PDs display excellent mechanical flexibility under wide range of bending conditions and thermal stability in the measured temperature range(5–50 ℃).The biodegradability studies performed on the device, in both deionized(DI) water(pH≈6) and PBS solution(pH=7.4),show fast degradability in DI water(20 mins) as compared to PBS(48 h). These results show the potential the presented approach holds for green and cost-effective fabrication of wearable, and disposable sensing systems with reduced adverse environmental impact.

Self-healing wearable self-powered deep ultraviolet photodetectors based on Ga_(2)O_(3)

Gallium oxide(Ga_(2)O_(3))based flexible heterojunction type deep ultraviolet(UV)photodetectors show excellent solar-blind photoelectric performance,even when not powered,which makes them ideal for use in intelligent wearable devices.How-ever,traditional flexible photodetectors are prone to damage during use due to poor toughness,which reduces the service life of these devices.Self-healing hydrogels have been demonstrated to have the ability to repair damage and their combination with Ga_(2)O_(3) could potentially improve the lifetime of the flexible photodetectors while maintaining their performance.Herein,a novel self-healing and self-powered flexible photodetector has been constructed onto the hydrogel substrate,which exhibits an excellent responsivity of 0.24 mA/W under 254 nm UV light at zero bias due to the built-in electric field originating from the PEDOT:PSS/Ga_(2)O_(3) heterojunction.The self-healing of the Ga_(2)O_(3) based photodetector was enabled by the reversible property of the synthesis of agarose and polyvinyl alcohol double network,which allows the photodetector to recover its original configu-ration and function after damage.After self-healing,the photocurrent of the photodetector decreases from 1.23 to 1.21μA,while the dark current rises from 0.95 to 0.97μA,with a barely unchanged of photoresponse speed.Such a remarkable recov-ery capability and the photodetector’s superior photoelectric performance not only significantly enhance a device lifespan but also present new possibilities to develop wearable and intelligent electronics in the future.

Fabrication and Characterization of Undoped and Cobalt-doped ZnO Based UV Photodetector Prepared by RF-sputtering

Undoped and 1 at.% Co-doped ZnO nanostructure based UV photodetectors were successfully fabricated by RF- magnetron sputtering technique with comb like Pt electrodes. Cobalt ions were successfully incorporated into the lattice of the ZnO nanostructure without changing its wurtzite structure. It was indicated that Co-doping can effectively adjust the luminescence properties of the ZnO nanostructure. The undoped and Co-doped ZnO photodetectors were observed to have photosensitivities of 1.44 x 104 % and 8.57 x 102 % and low dark currents of 9.74 x 10-8 A and 1.18 x 10-7 A, respectively.

A self-powered ultraviolet photodetector based on a Ga_(2)O_(3)/Bi_(2)WO_(6)heterojunction with low noise and stable photoresponse

A self-powered solar-blind ultraviolet(UV)photodetector(PD)was successfully constructed on a Ga_(2)O_(3)/Bi_(2)WO_(6)heterojunction,which was fabricated by spin-coating the hydrothermally grown Bi_(2)WO_(6)onto MOCVD-grown Ga_(2)O_(3)film.The results show that a typical type-I heterojunction is formed at the interface of the Ga_(2)O_(3)film and clustered Bi_(2)WO_(6),which demonstrates a distinct photovoltaic effect with an open-circuit voltage of 0.18 V under the irradiation of 254 nm UV light.Moreover,the Ga_(2)O_(3)/Bi_(2)WO_(6)PD displays excellent photodetection performance with an ultra-low dark current of~6 fA,and a high light-to-dark current ratio(PDCR)of 3.5 x 10^(4)in self-powered mode(0 V),as well as a best responsivity result of 2.21 mA/W in power supply mode(5 V).Furthermore,the PD possesses a stable and fast response speed under different light intensities and voltages.At zero voltage,the PD exhibits a fast rise time of 132 ms and 162 ms,as well as a quick decay time of 69 ms and 522 ms,respectively.In general,the newly attempted Ga_(2)O_(3)/Bi_(2)WO_(6)heterojunction may become a potential candidate for the realization of self-powered and high-performance UV photodetectors.

Investigation of UV photosensor properties of Al-doped SnO_(2) thin films deposited by sol-gel dip-coating method

Transparent conducting aluminum doped tin oxide thin films were prepared by sol-gel dip coating method with differ-ent Al concentrations and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Vis spectrophotometry and photoconductivity study. The variation observed in the properties of the measured films agrees with a difference in the film's thickness, which decreases when Al concentration augments. X-ray diffraction analysis reveals that all films are polycrystal-line with tetragonal structure, (110) plane being the strongest diffraction peak. The crystallite size calculated by the Debye Scher-rer’s formula decreases from 11.92 to 8.54 nm when Al concentration increases from 0 to 5 wt.%. AFM images showed grains uni-formly distributed in the deposited films. An average transmittance greater than 80% was measured for the films and an en-ergy gap value of about 3.9 eV was deduced from the optical analysis. Finally, the photosensitivity properties like current-voltage characteristics, ION/IOFF ratio, growth and decay time are studied and reported. Also, we have calculated the trap depth energy using the decay portion of the rise and decay curve photocurrent.

Ultraviolet photodetectors based on ferroelectric depolarization field

Ultraviolet(UV)photodetectors are extensively adopted in the fields of the Internet of Things,optical communications and imaging.Nowadays,with broadening the application scope of UV photodetectors,developing integrated devices with more functionalities rather than basic photo-detecting ability are highly required and have been triggered ever-growing interest in scientific and industrial communities.Ferroelectric thin films have become a potential candidate in the field of UV detection due to their wide bandgap and unique photovoltaic characteristics.Additionally,ferroelectric thin films perform excellent dielectric,piezoelectric,pyroelectric,acousto-optic effects,etc.,which can satisfy the demand for the diversified development of UV detectors.In this review,according to the different roles of ferroelectric thin films in the device,the UV photodetectors based on ferroelectric films are classified into ferroelectric depolarization field driven type,ferroelectric depolarization field and built-in electric field co-driven type,and ferroelectric field enhanced type.These three types of ferroelectric UV photodetectors have great potential and are expected to promote the development of a new generation of UV detection technology.At the end of the paper,the advantages and challenges of three types of ferroelectric UV photodetectors are summarized,and the possible development direction in the future is proposed.

Hybrid UV photodetector with high photo-to-dark current ratio based on ordered TiO_2 nanorod arrays and polystyrene sulfate

Vertically aligned TiO2nanorods arrays were successfully synthesized on FTO glass by wet-chemical method.Based on polystyrene sulfate(PSS)functionalized TiO2nanorods arrays,a sandwich-structured hybrid UV photodetector was fabricated.The photo-to-dark current ratio of the device increases by more than 3 orders of magnitude with typical case,while the dark current is about 10 nA at 1 V bias.The high photoresponse together with the low dark current could probably contribute a large photocurrent and low-power application.The high performance of the hybrid material and facile low-cost fabrication of the UV detector make the devices promising for large-area UV photodetection applications.

Recent progress of ZnMgO ultraviolet photodetector

The ultra-violet（UV） detection has a wide application in both civil and military fields.ZnO is recognized as one of ideal materials for fabricating the UV photodetectors due to its plenty of advantages,such as wide bandgap,low cost,being environment-friendly,high radiation hardness,etc.Moreover,the alloying of ZnO with MgO to make ZnMgO could continually increase the band gap from ~ 3.3 eV to ~ 7.8 eV,which allows both solar blind and visible blind UV radiation to be detected.As is well known,ZnO is stabilized in the wurtzite structure,while MgO is stabilized in the rock salt structure.As a result,with increasing the Mg content,the crystal structure of ZnMgO alloy will change from wurtzite structure to rock salt structure.Therefore,ZnMgO photodetectors can be divided into three types based on the structures of alloys,namely,wurtzite-phase,cubic-phase and mixed-phase devices.In this paper,we review recent development and make the prospect of three types of ZnMgO UV photodetectors.

Review of deep ultraviolet photodetector based on gallium oxide

Ultraviolet(UV) photodetectors(PDs) have drawn great attention in recent years due to their potential application in civil and military fields. Because of its ultrawide bandgap, low cost, strong radiation hardness, and high thermal and chemical stability with high visible-light transparency, Ga_2O_3 is regarded as the most promising candidate for UV detection.Furthermore, the bandgap of Ga_2O_3 is as high as 4.7–4.9 eV, directly corresponding to the solar-blind UV detection band with wavelength less than 280 nm. There is no need of doping in Ga_2O_3 to tune its bandgap, compared to AlGaN, MgZnO,etc, thereby avoiding alloy composition fluctuations and phase separation. At present, solar-blind Ga_2O_3 photodetectors based on single crystal or amorphous Ga_2O_3 are mainly focused on metal–semiconductor–metal and Schottky photodiodes.In this work, the recent achievements of Ga_2O_3 photodetectors are systematically reviewed. The characteristics and performances of different photodetector structures based on single crystal Ga_2O_3 and amorphous Ga_2O_3 thin film are analyzed and compared. Finally, the prospects of Ga_2O_3 UV photodetectors are forecast.

A novel integrated ultraviolet photodetector based on standard CMOS process

A novel integrated ultraviolet（UV） photodetector has been proposed, which realizes a high UV selectivity by combining a conventional UV-selective photodiode with an extra infrared（IR） photodiode. The IR photodiode is designed for compensating the photocurrent response of the UV photodiode in the infrared band and is 15 times smaller than the UV one. The integrated photodetector has been fabricated in a 0.35 μm standard CMOS technology. Some critical performance indices of this new structure photodetector, such as spectral responsivity, breakdown voltage, quenching waveform, and transient response, are measured and analyzed. Test results show that the complementary UV–IR photodetector has a maximum spectral responsivity of 0.27 A·W-1 at the wavelength of 400 nm. The device has a high UV selectivity of 3000,which is much higher than that of the single UV photodiode.

Cu掺杂β-Ga_(2)O_(3)薄膜的制备及紫外探测性能

β-Ga_(2)O_(3)作为第三代宽禁带半导体材料,具有禁带宽度大(4.9 eV)、击穿电场强,吸收边正好位于日盲紫外波段(波长200—280 nm)内,且在近紫外以及整个可见光波段具有较高的透过率,使得β-Ga_(2)O_(3)是一种非常适合制作日盲紫外光电探测器的材料.目前在p型β-Ga_(2)O_(3)材料方面的研究还较少,但p型β-Ga_(2)O_(3)材料的制备对于其光电器件的应用至关重要,因此成功制备p型β-Ga_(2)O_(3)材料就显得尤为关键.采用化学气相沉积法在蓝宝石衬底上生长出不同Cu掺杂量的β-Ga_(2)O_(3)薄膜,并对薄膜的形貌、晶体结构和光电特性进行了测试.发现随着Cu掺杂量的增加,样品(201)晶面的衍射峰向小角度方向发生了移动,这说明Cu2+替代了Ga3+进入到了Ga2O3晶格中.此外,在Cu掺杂β-Ga_(2)O_(3)薄膜上蒸镀Au作为叉指电极,制备出了金属-半导体-金属结构光电导型日盲紫外探测器,并对其紫外探测性能进行了研究.结果表明,在10 V偏压、254 nm波长紫外光下,器件的光暗电流比约为3.81×102,器件的上升时间和下降时间分别是0.11 s和0.13 s.此外,在光功率密度为64μW/cm2时,器件的响应度和外部量子效率分别是1.72 A/W和841%.

Ga_(2)O_(3)/p-GaN异质结自供电日盲紫外光探测器的制备与光电性能研究

采用水热法在p-GaN衬底上生长Ga_(2)O_(3)纳米棒阵列,构建了Ga_(2)O_(3)/p-GaN异质结自供电日盲紫外光探测器。首先对异质结的形貌和结构性能进行了研究,并进一步对异质结紫外光探测器的伏安特性和紫外光探测性能进行了探索。结果表明在0 V偏压和254 nm紫外光照下,器件表现出明显的自供电日盲紫外光响应,响应度为718.8 mA/W,并具有良好的稳定性和重复性。结合异质结能带理论对器件的自供电紫外光响应机理进行了讨论。

基于氧化镓探测器的日盲紫外光通信系统的设计与实现

为克服传统光电探测器工作电压较高、硬件电路复杂与抗干扰能力差的问题,设计了一种基于新型氧化镓探测器的日盲紫外光通信系统。该系统在给定窗口大小的情况下,根据设计的数据处理算法对光强进行实时动态监测,通过将计算得到的阈值与光强作比较输出二值信号,结合OOK调制技术、驱动电路与非相干解调技术,实现了日盲紫外光通信系统。进一步从调制技术、驱动电路以及数据处理算法三个方面对通信系统进行仿真与实验测试,验证该系统的功能完整性、系统简洁性与可靠性。结果表明:该日盲紫外光通信系统在准确接收信号的情况下,可以直接实现将光强值转化为二值信号输出,且误码率小于10-3,能够达到简化接收端硬件电路以及提升硬件电路可靠性的目的。该系统编码简单可靠、易实现且抗干扰能力强,无需滤波装置、小巧便携、可靠性高,为日盲紫外光通信系统的优化与便携使用提供了新思路。

PEDOT的固相聚合法制备及其在紫外光探测器中的应用

首先以2,5-二溴-3,4-乙撑二氧噻吩(DBEDOT)为单体,通过固相聚合法在掺杂氟的二氧化锡导电玻璃(FTO)基底表面制备聚(3,4-乙撑二氧噻吩)(PEDOT)膜,然后将其与氧化锌纳米阵列(ZnO NRs)修饰的FTO组装成有机-无机异质结紫外光探测器,并研究其紫外光探测性能。采用紫外-可见分光光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)、X射线衍射光谱(XRD)等测试方法对材料进行表征。结果表明,固相聚合法制备的PEDOT能有效提升ZnO NRs基紫外光探测器的性能。器件在紫外光照射下(365 nm,0.32 mW/cm^(2))表现出较高响应度(15.34 mA/W)、较短响应时间(上升时间为0.159 s,下降时间为0.162 s)和较好的稳定性。

高性能柔性滤膜基铌酸钙纳米片紫外探测器

通过简单的固相反应和液相剥离方法制备铌酸钙(Ca_(2)Nb_(3)O_(10))纳米片,Ca_(2)Nb_(3)O_(10)纳米片再利用简单的抽滤方法集成到滤膜孔中.该滤膜和Ca_(2)Nb_(3)O_(10)纳米片一体化紫外探测器除了表现出高响应率、大探测率和快响应速度之外,还表现出良好的柔韧性.这项工作为实现基于滤膜和二维材料的高性能柔性光电器件提供了新思路.