Analysis of I-V Thermal Characteristic on GaN-based p-i-n Ultraviolet Detector

The I-V characteristic of GaN-based p-i-n ultraviolet detector is presented. It is measured at different temperatures and analyzed with changing temperature. The ideality factor of the device is 2.09 at room temperature. The maximum ideality factor is 2.14 at 100 ℃, which declines above 100 ℃, and the minimum ideality factor is 1.26 at 300 ℃. The coefficient of forward voltage vs. temperature is -1.97 mV/℃ with a forward current of 1 mA. Based on double injection model, the deep lying impurity activation energy in the i-region is 0.1 343 eV.

High-speed performance self-powered short wave ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)

High-speed solar-blind short wavelength ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)layers with Pt contacts were demonstrated and their properties were studied in detail.Theκ(ε)-Ga_(2)O_(3)layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates.The spectral dependencies of the photoelectric properties of struc-tures were analyzed in the wavelength interval 200-370 nm.The maximum photo to dark current ratio,responsivity,detectiv-ity and external quantum efficiency of structures were determined as:180.86 arb.un.,3.57 A/W,1.78×10^(12) Hz^(0.5)∙cm·W^(-1) and 2193.6%,respectively,at a wavelength of 200 nm and an applied voltage of 1 V.The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)-Ga_(2)O_(3)interface under ultraviolet exposure.The detectors demon-strated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga_(2)O_(3)interface.The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%,respectively.The rise and decay times in self-powered mode did not exceed 100 ms.

A novel model of photo-carrier screening effect on the GaN-based p-i-n ultraviolet detector

The photo-carrier density in the depletion region of the GaN-based p-i-n ultraviolet(UV) detector is calculated by solving the photo-carrier continuity equation,and the photo-carrier screening electric field is calculated according to Poisson's equation.Using the numerical calculation method,a novel model of photo-carrier screening effect is presented.Then the influence of photo-carrier screening effect on the distribution of photo-carrier density in the depletion region of p-i-n detector is discussed.The influence of incident power,bias voltage and carrier life time on the photo-carrier screening effect is also analyzed.It is concluded that the influence of photo-carrier screening effect on the performance of GaN-based p-i-n UV detector is non-monotone,the maximum of carrier drift velocity and the minimum of response time can be realized by adjusting the applied voltage.Besides,the incident light duration has strong impact on the photo-carrier screening effect.

Self-powered UVC detectors based on α-Ga_(2)O_(3) with enchanted speed performance

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet(UVC)interval using high-quality single-crystallineα-Ga_(2)O_(3) films with Pt interdigital contacts.The films ofα-Ga_(2)O_(3) were grown on planar sapphire substrates with c-plane orientation using halide vapor phase epitaxy.The spectral dependencies of the photo to dark current ratio,responsivity,external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 nm.The maximum of photo to dark current ratio,responsivity,external quantum efficiency,and detectivity of the structures were 1.16×10^(4) arb.un.,30.6 A/W,1.65×10^(4)%,and 6.95×10^(15) Hz^(0.5)·cm/W at a wavelength of 230 nm and an applied voltage of 1 V.The high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole trapping.Theα-Ga_(2)O_(3) film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga_(2)O_(3) interfaces.At a wavelength of 254 nm and zero applied voltage,the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2×10^(−2)%.The UVC detectors based on theα-Ga_(2)O_(3) films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.

Review of improved spectral response of ultraviolet photodetectors by surface plasmon

Ultraviolet(UV) photodetectors based on wide band gap semiconductor have attracted much attention for their small volume, low working voltage, long lifetime, good chemical and thermal stability. Up to now, many researches have been done on the semiconductors based UV detectors and some kinds of detectors have been made, such as metal–semiconductor–metal(MSM), Schottky, and PIN-type detectors. However, the sensitivity values of those detectors are still far from the expectation. Recent years, surface plasmon(SP) has been considered to be an effective way to enhance the sensitivity of semiconductor based UV photodetector. When the light is matched with the resonance frequency of surface plasmon, the localized field enhancement or scattering effect will happen and thus the spectral response will be enhanced.Here, we present an overview of surface plasmon enhancing the performance of UV detectors, including the GaN, ZnO,and other wide band gap semiconductor UV detectors. Both fundamental and experimental achievements are contained in this review.

Graded composition and doping p-i-n Al_(x)Ga_(1−x)As/GaAs detector for unbiased voltage operation

p-i-n Al_(x)Ga_(1−x)As/GaAs detectors with graded compositions and graded doping were grown and prepared.From the current-voltage and capacitance-voltage measurement results,the devices had good p-n junction diode characteristics,and the electric field strength under an unbiased voltage was 1.7×10^(5) Vcm^(-1).The full width at half maximum and charge collection efficiency of the detectors obtained from energy spectrum measurements of 5.48-MeV alpha particles were 3.04 and approximately 93%,respectively.In this study,we created the most advanced and promising state-of-the-art unbiased detector reported to date.

Ultraviolet ZnO Photodetectors with High Gain

Fabrication and characterization of metal-semiconductor-metal ultraviolet （MSM UV） photodetector based on ZnO ultra thin （nano scale） films with Pd Schottky contact are reported. The ZnO thin film was grown on glass substrate by thermal oxidation of preeposited zinc films using vacuum deposition technique. With applied voltage in the range from -3V to 3V, the contrast ratio, responsivity, and detectivity for an incident radiation of 0.1 mW at 365 nm wavelength were estimated. The proposed device exhibited a high gain which was attributed to the hole trapping at semiconductor-metal interface. I-V characteristics were studied and the parameters, such as ideality factor, leakage current, resistance-areaproduct, and barrier height, were extracted from the measured data.

Middle and near ultraviolet spectrograph of the Scientific Experimental system in Near SpacE(SENSE)

The Scientific Experimental system in Near SpacE(SENSE)consists of different types of instruments that will be installed on a balloon-based platform to characterize near-space environmental parameters.As one of the main scientific payloads,the middle and near ultraviolet spectrograph(MN-UVS)will provide full spectra coverage from middle ultraviolet(MUV,200−300 nm)to near ultraviolet(NUV,300−400 nm)with a spectral resolution of 2 nm.Its primary mission is to acquire data regarding the UV radiation background of the upper atmosphere.The MN-UVS is made up of six primary components:a fore-optical module,an imaging grating module,a UV intensified focal plane module,a titanium alloy frame,a spectrometer control module,and a data processing module.This paper presents in detail the engineering design of each functional unit of the MN-UVS,as well as the instrument’s radiometric calibration,wavelength calibration,impact test,and low-pressure discharge test.Furthermore,we are able to report ground test and flight test results of high quality,showing that the MN-UVS has a promising future in upcoming near-space applications.

高性能背照式GaN/AlGaN p-i-n紫外探测器的制备与性能

研究了GaN/AlGaN异质结背照式p-i-n结构可见盲紫外探测器的制备与性能。GaN/AlGaN外延材料采用金属有机化学气相沉积(MOCVD)方法生长,衬底为双面抛光的蓝宝石,缓冲层为AlN,n型层采用厚度为0.8μm的Si掺杂Al0.3Ga0.7N形成窗口层,i型层为0.18μm的非故意掺杂的GaN,p型层为0.15μm的Mg掺杂GaN。采用Cl2、Ar和BCl3感应耦合等离子体刻蚀定义台面,光敏面面积为1.96×10-3 cm2。可见盲紫外探测器展示了窄的紫外响应波段,响应区域为310～365 nm,在360 nm处响应率最大,为0.21 A/W,在考虑表面反射时,内量子效率达到82%;优质因子R0A为2.00×108Ω.cm2,对应的探测率D=2.31×1013 cm.Hz1/2.W-1;且零偏压下的暗电流为5.20×10-13 A。

背照式GaN/AlGaN p-i-n紫外探测器的制备与性能

文章研究了p-GaN／i—GaN／n-Al0.3Ga0.7N异质结背照式p-i—n可见盲紫外探测器的制备与性能。器件的响应区域为310～365nm，最大响应率为0．046A/W，对应的内量子效率为19％，优值因子R0A达到1．77×10^8Ω·cm^2，相应的在363nm处的探测率D^＊=2．6×10^12cmHz^1/2W^-1。

基于石墨电极的硅基金刚石日盲紫外探测器

金刚石优异的材料特性使其在日盲紫外探测领域有很大的应用潜力。本文采用微波等离子体化学气相沉积设备在(111)晶面单晶硅衬底上沉积金刚石薄膜,并基于该薄膜采用光刻胶热解法制备石墨材料平面叉指电极MSM结构金刚石日盲紫外探测器,为全碳金刚石探测器的实现提供了新方法。结果表明,该硅基金刚石薄膜为高取向多晶薄膜,(111)晶面的XRD 2θ扫描半峰宽为0.093°,拉曼光谱金刚石特征峰峰位1332 cm^(-1),半峰宽为4 cm^(-1),薄膜晶体质量较高;石墨电极紫外探测器在5 V偏置电压下的暗电流为2.07×10^(-8) A,光暗电流比为77,开关特性良好,并且石墨电极探测器具有优异的时间响应,上升时间为30 ms,下降时间为430 ms。

多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结的制备及紫外探测性能研究

本文首先采用紫外光辅助电化学刻蚀(UV-EC)方法制备出了孔隙密度为1.51×10^(10)cm^(-2)、平均孔径为38 nm的多孔n-GaN薄膜;随后在其上通过水浴法沉积了一系列Zn_(x)Cu_(1-x)S复合薄膜,x为0.0、0.2、0.4、0.6、0.8、1.0,形成的多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结带隙在2.34~3.51 eV调控;最后基于这些异质结构建出p-n结型紫外探测器。I-V曲线结果表明这些探测器均具有良好的整流特性,特别是n-GaN/p-Zn_(0.4)Cu_(0.6)S探测器性能最优。在暗态下,I_(+3 V)/I_(-3 V)约为1.78×10~5;在偏压为-3 V、光功率密度为432μW/cm^(2)(365 nm)的条件下,光暗电流比超过10~3,上升/下降时间为0.09/39.8 ms,响应度(R)为0.352 A/W,外量子效率(EQE)为119.6%,探测率(D^(*))为3.21×10^(12)Jones。I-t曲线结果表明,多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结紫外探测器在连续开-关光循环过程中拥有稳定的光电流响应。该研究为制备异质结紫外探测器提供了一定的理论指导和实验数据。

离子交换色谱-紫外检测器法测定马铃薯中马来酰肼的残留量

提出了离子交换色谱-紫外检测器法测定马铃薯中马来酰肼残留量的方法。称取1 g洗净、去皮、搅碎的马铃薯样品,加入10 mL甲醇,超声提取30 min,于60℃水浴加热5 min,离心20 min,取上清液过0.22μm滤膜和反相前处理柱。采用Dionex IonPac AS16分析柱和Dionex IonPac AG16保护柱分离,KOH溶液梯度洗脱,在205 nm波长下进行检测。结果表明:马来酰肼的质量浓度在0.1825~10.14 mg·L^(-1)内与对应的峰面积呈线性关系,检出限(3S/N)为0.06 mg·L^(-1);按照标准加入法进行回收试验,马来酰肼回收率为97.9%~108%;柱温、流量和紫外检测波长的微小改变,对MH的检测均没有影响;方法用于实际马铃薯样品分析,均未检出马来酰肼。

AlGaN基p-i-n型日盲紫外探测器材料的研制

采用金属有机气相外延(MOCVD)方法在(0001)面蓝宝石衬底上生长了AlN和高铝组分AlGaN材料。通过优化AlN和AlGaN材料的生长温度、生长压力和Ⅴ族元素/Ⅲ族元素物质的量比(nⅤ/Ⅲ)等工艺条件,得到了高质量的AlN和高铝组分AlGaN材料。AlN材料X射线双晶衍射ω(002)半宽为74 arcsec,透射光谱测试带边峰位于205 nm,带边陡峭;Al组分为45%的AlGaN材料X射线双晶衍射ω(002)半宽为223 arcsec,透射光谱测试带边峰位于272 nm,带边陡峭。采用此外延工艺方法生长了AlGaN基p-i-n型日盲紫外探测器材料并进行了器件工艺流片,研制出AlGaN基p-i-n型日盲紫外探测器,响应峰值波长为262 nm,在零偏压下的峰值响应度达到0.117 A/W。

基于GaN/(BA)_(2)PbI_(4)异质结的自供电双模式紫外探测器

紫外探测器作为智能光电系统的重要组成部分,近年来在诸多领域应用广泛,其中自供电异质结光电二极管的研究显得尤为重要.本文制备并讨论了一种双模式运行的GaN/(BA)_(2)PbI_(4)异质结紫外光电二极管.通过金属有机化学气相沉积法在蓝宝石上沉积GaN薄膜,再在GaN薄膜表面旋涂(BA)_(2)PbI_(4)薄膜,用于构建平面异质结探测器.当在+5 V偏压驱动、光强为421μW/cm^(2)的365 nm紫外光照射下,响应度(R)和外量子效率(EQE)分别为60 mA/W和20%.在自供电模式下,上升时间(τ_(r))和衰减时间(τ_(d))分别为0.12 s和0.13 s.这些结果共同证明了基于GaN/(BA)_(2)PbI_(4)异质结的自供电紫外光电二极管拥有旷阔的发展前景,为智能光电系统的发展提供了新的思路.

2维SnO_(x)/Ga_(2)O_(3)异质结的制备及其探测器的光电性能

紫外探测器在天文、军事、医学等方面具有重要应用前景.采用液态金属转移法制备2维SnO_(x)/Ga_(2)O_(3)异质结,并构建2维SnO_(x)/Ga_(2)O_(3)异质结紫外探测器,研究2维异质结紫外探测器的光电性能.研究结果表明:该文探测器具有良好的光电性能,有潜在应用价值.

GaN基p-i-n和肖特基紫外探测器的响应光谱及暗电流特性

研究了p-i-n型和肖特基型Ga N基紫外探测器的响应光谱和暗电流特性。实验发现,随着p-Ga N层厚度的增加,p-i-n型紫外探测器的响应度下降,并且在短波处下降更加明显。肖特基探测器的响应度明显比pi-n结构高,主要是由于p-Ga N层吸收了大量的入射光所致。肖特基型紫外探测器的暗电流远远大于p-i-n型紫外探测器的暗电流,和模拟结果基本一致,主要是肖特基型探测器是多子器件,而p-i-n型探测器是少子器件。要制备响应度大、暗电流小的高性能Ga N紫外探测器,最好采用p-Ga N层较薄的p-i-n结构。

GaN p-i-n紫外探测器的研制

研制了一种GaN p-i-n型单元器件,详细地讨论了该器件的制备工艺,并对该器件进行了光电性能测试.测试结果表明,器件的正向开启电压在2 V左右,零偏动态电阻R0约为1010～1011 Ω,最大峰值响应率在365 nm处为0.18～0.21 A/W,器件的上升响应时间和下降时间分别为2.8和13.4 ns.

Slow-rise and fast-drop current feature of ultraviolet response spectra for ZnO-nanowire film modulated by water molecules

This study describes the fabrication of ZnO-nanowire films by electro-chemical anodization of Zn foil. The ZnO films are characterized by field emission scanning electron microscopy, X-ray diffraction patterns, and transmission electron microscopy, respectively. The ultraviolet （UV） photo-response properties of the surface-contacted ZnO film are studied through the current evolution processes under different relative humidities. Unlike the usually observed current spectra of the ZnO films, the drop time is shorter than the rise time. The photo-conductivity gain G and the response time T are both increased with the increase of the applied bias. The photo-conductivity gain G is lowered with the increase of the environmental humidity, while the response time τ- is increased. These results can be explained by considering three different surface processes： 1） the electron-hole （e-p） pair generation by the UV light illumination, 2） the following surface O2 species desorption, and 3） the photo-catalytic hydrolysis of water molecules adsorbed on the ZnO surface. The slow-rise and fast-drop current feature is suggested to originate from the sponge-like structure of the ZnO nanowires.