InGaAs-MSM光电探测器设计与仿真研究

对基于InGaAs材料体系的金属 半导体 金属（metal semiconductor metal,MSM）光电探测器进行设计,并对其暗电流、光电流、电容以及截止频率等性能参数进行仿真。通过添加InAlAs肖特基势垒增强层,将探测器的暗电流减小到了pA量级。仿真结果表明,探测器在光照下有明显的光响应,通过合理设计器件结构,探测器的工作频率可以达到1.5 THz。制备了探测器样品,并对其暗电流和光响应进行了测试,测试结果与仿真结果基本吻合。     

不同钝化结构对非极性AlGaN-MSM紫外探测器性能的提升

在r面蓝宝石衬底上,采用金属有机化学气相沉积（MOCVD）法高温生长了未掺杂非极性AlGaN半导体薄膜,在此基础上制备了金属-半导体-金属（MSM）结构的紫外探测器。系统研究了在AlGaN半导体薄膜表面分别磁控溅射SiO₂纳米颗粒与SiO₂钝化层两种钝化手段对非极性AlGaN-MSM结构的紫外探测器性能的影响。实验结果表明：磁控溅射SiO₂纳米颗粒钝化或SiO₂钝化层两种手段都能提升AlGaN-MSM结构紫外探测器性能。暗电流测试表明,SiO₂纳米颗粒和SiO₂钝化层可使器件暗电流下降1~2个数量级,达到nA量级。光谱响应测试发现,在5 V偏压下,探测器在300 nm处具有陡峭的截止边,这表明其具有很好的深紫外特性,光谱响应提高了10³倍,紫外可见抑制比高达10⁵。     

Metal-semiconductor-metal ultraviolet photodetector based on GaN

A metal-semiconductor-metal (MSM) ultraviolet photodetector has been fabricated using unintentionally doped n-GaN films grown on sapphire substrates. Its dark current, photocurrent under the illumination with λ = 360 nm light, responsivity, and the dependence of responsivity on bias voltage were measured at room temperature. The dark current of the photodetector is 1.03 Na under 5 V bias, and is 15.3 Na under 10 V bias. A maximum responsivity of 0.166 A/W has been achieved under the illumination with λ= 366 nm light and 15 V bias. It exhibits a typical sharp band-edge cutoff at the wavelength of 366 nm, and a high responsivity at the wavelength from 320 nm to 366 nm. Its responsivity under the illumination with λ= 360 nm light increases when the bias voltage increases.     

采用Al/TaN叠层电极提高Si基Ge PIN光电探测器的性能

金属与Ge材料接触由于存在强烈的费米钉扎效应, 导致金属电极与n型Ge接触引入较大的接触电阻, 限制了Si基Ge探测器响应带宽. 本文报道了在SOI衬底上外延Ge单晶薄膜并制备了不同台面尺度的Ge PIN光电探测器. 对比了电极分别为金属Al和Al/TaN叠层的具有相同器件结构的SOI基Ge PIN光电探测器的暗电流、响应度以及响应带宽等参数. 发现在Al与Ge之间增加一薄层TaN可有效减小n型Ge的接触电阻, 将台面直径为24 μ的探测器在1.55 μ的波 长和-1 V偏压下的3 dB响应带宽提高了4倍. 同时, 器件暗电流减小一个数量级, 而响应度提高了2倍. 结果表明, 采用TaN薄层制作金属与Ge接触电极, 可有效钝化金属与Ge界面, 减轻费米钉扎效应, 降低金属与n-Ge接触的势垒高度, 因而减小接触电阻和界面复合电流, 提高探测器的光电性能.     

结构参数对GaN肖特基紫外探测器性能的影响及器件设计

研究了GaN肖特基结构(n^--GaN /n⁺-GaN)紫外探测器的结构参数对器件性能的影响机理。模拟计算结果表明:提高肖特基势垒高度和减小表面复合速率,不仅可以增加器件的量子效率,而且可以极大地减小器件的暗电流;适当地增加n^--GaN层厚度和载流子浓度可以提高器件的量子效率,但减小n^--GaN层的载流子浓度却有利于减小器件的暗电流。我们针对实际应用的需要,提出了一个优化器件结构参数的设计方案,特别是如果实际应用中对器件的量子效率和暗电流都有较高的要求,肖特基势垒高度应该≥0.8 eV,n^--GaN层的厚度≥200 nm,载流子浓度1×10¹⁷ cm^-3 左右,表面复合速率＜1×10⁷ cm/s。     

SiO2纳米颗粒对a-AlGaN金属-半导体-金属结构紫外探测器的影响

采用对a-AlGaN表面沉积SiO₂纳米颗粒制备工艺得到了金属-半导体-金属(MSM)结构的a-AlGaN紫外探测器。与没有沉积SiO₂纳米颗粒的探测器件相比,沉积SiO₂纳米颗粒使器件的暗电流下降了一个数量级,峰值光谱响应度提高了近3个数量级,紫外/可见抑制比大于10³。     

Large area InAlAs/InGaAs metal semiconductor metal photodiode with very low dark current and its frequency response

An MBE grown InGaAs metal semiconductor metal (MSM) photodiode (PD) with an InAlAs barrier enhancement layer is reported that has very low dark current and high speed characteristics. The detector using Cr/Au Schottky metal fingers with 4m spacing on a large active area of 300×300m2 shows a low dark current of 38nA at 10V. This corresponds to a dark current density of 0.42pA/m2 and is, to our knowledge, the best dark current ever obtained from a large area InGaAs MSM PD. The device also shows a low capacitance of 0.8pF and a high 3dB bandwidth of 2.4GHz. By fitting the measured frequency response to a model consisting of both RC time and transit time limited responses, we show that the device has an RC time and a transit time limited 3dB bandwidth of 3.0 and 4.9GHz, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

一种减小GaN基肖特基结构紫外探测器暗电流的方法

提出了一种减小GaN肖特基结构紫外探测器暗电流的方法.该方法是在普通的GaN肖特基结构的表面增加一层薄的p-GaN.模拟计算结果表明,该层p-GaN能增加肖特基势垒高度,从而减小了器件的暗电流,提高了器件性能.进一步的计算还发现,对于p型载流子浓度较高的情况下,只需要很薄的一层p-GaN就能显著增加肖特基势垒高度,对于p型载流子浓度较低的情况下,则需要较厚的一层p-GaN才能有较好的肖特基势垒高度增加效果. 关键词： GaN 肖特基结构 紫外探测器 暗电流     

背入射Au/ZnO/Al结构肖特基紫外探测器

设计制作了一种Au/ZnO/Al结构的紫外探测器,光的入射方式采用背入射式。ZnO薄膜是用磁控溅射在蓝宝石衬底上制备的。I-V测试表明:Au与ZnO形成了肖特基接触。得到探测器的光响应峰值在352nm,截止边为382nm,可见抑制比达一个量级。由于该探测器是一种垂直结构器件,对于进一步实现ZnO紫外探测器阵列及单光子探测有很好的研究价值。     

Electrical,optical and spectral characteristics of type-II ZnSe/ZnTe/GaAs superlattice and MSM-photodetector on their base

We report on growth, fabrication and characterization of the metal–semiconductor–metal (MSM) photodiode based on type-II ZnSe/ZnTe heterostructure. Heterostructure was grown on semi-insulating GaAs substrates by MOVPE. For the first time we present the results of experimental investigations of the MSM photodetector on the base of type-II ZnSe/ZnTe superlattice. The MSM-photodetector demonstrates very low dark current, high current sensitivity and external quantum efficiency. The maximum photoresponse of the MSM-detector at the wavelength 620 nm corresponds to current sensitivity 0.22 A/W and external quantum efficiency 44%. Photoresponse of the MSM-detector shows two peaks of response located at 620 nm and 870 nm. ZnSe/ZnTe type-II superlattice structure reduces the MSM-diode dark current significantly. For the MSM-diode with finger width and gap of 3 µm and 100?×?100 µm² photosensitive area we have obtained dark current density 10^?8 A/cm² at room temperature.     

Theoretical optimization of the characteristics of ZnO metal-semiconductor-metal photodetectors

A two-dimensional model of a metal-semiconductor-metal(MSM) ZnO-based photodetector(PD) is developed.The PD is based on a drift diffusion model of a semiconductor that allows the calculation of potential distribution inside the structure,the transversal and longitudinal distributions of the electric field,and the distribution of carrier concentration.The ohmicity of the contact has been confirmed.The dark current of MSM PD based ZnO for different structural dimensions are likewise calculated.The calculations are comparable with the experimental results.Therefore,the influence with respect to parameters s(finger spacing) and w(finger width) is studied,which results in the optimization of these parameters.The best optimization found to concur with the experimental results is s = 16 μm,w = 16 μm,l = 250 μm,L = 350 μm,where l is the finger length and L is the length of the structure.This optimization provides a simulated dark current equal to 24.5 nA at the polarization of 3 V.     

MSM结构Mg0.2Zn0.8O可见盲光电探测器

采用射频磁控溅射,通过传统的紫外曝光和湿法腐蚀的方法,制备了不同电极间距的金属-半导体-金属(MSM)结构Mg0.2Zn0.8O可见盲光电探测器.研究了器件的暗电流和响应度随电极间距的变化关系,当施加的电压没有达到贯穿电压的时候,暗电流和响应度均随着电极间距的增加而减小,并对其具体的机制进行了研究.     

Enhancing photoresponse time of low cost Pd/ZnO nanorods prepared by thermal evaporation techniques for UV detection

High quality undoped ZnO nanorods have been synthesized at 850 °C by vapor-solid (VS) technique without a catalyst through a low cost process on silicon substrates. Then, ZnO nanorods have been characterized by using scanning electron microscopy (SEM), X-ray diffractometer (XRD), and photoluminescence (PL) spectroscopy. Metal-semiconductor-metal (MSM) photodetectors with palladium (Pd) as contact electrodes have been successfully constructed for ultraviolet (UV) detection. Under dark and UV illumination, the load resistance of the Pd/ZnO junction was found to be 80.4 kΩ, and 23.5 kΩ referring to the maximum allowed bias voltage; the barrier height was estimated to be about 0.8 eV, and 0.76 eV, at 5 V applied bias voltage, respectively. It was found that the maximum responsivity of the Pd/ZnO MSM photodetector was 0.106 A/W at 300 nm which corresponds to a quantum efficiency of 43.8% at 5 V applied bias voltage. The transient photoresponse of the fabricated device is reported under different applied biases at 1 V, 3 V, and 5 V.     

Performance Improvement of GaN Based Schottky Barrier Ultraviolet Photodetector by Adding a Thin A1GaN Window Layer

We propose a new structure of GaN based Schottky barrier ultraviolet photodetector, in which a thin n-type A1GaN window layer is added on the conventional n^--GaN/n^＋-GaN device structure. The performance of the Schottky barrier ultraviolet photodetector is found to be improved by the new structure. The simulation result shows that the new structure can reduce the negative effect of surface states on the performance of Schottky barrier GaN photodetectors, improving the quantum efficiency and decreasing the dark current. The investigations suggest that the new photodetector can exhibit a better responsivity by choosing a suitably high carrier concentration and thin thickness for the A1GaN window layer.     

High responsivity 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors

4H-SiC based metal-semiconductor-metal (MSM) photodetectors with diverse spacing were designed, fabricated, and characterized, in which nickel Schottky contacts were needed. Current-voltage and spectral responsivity measurements were carried out at room temperature. The fabricated 4 μm-spacing device showed a very low dark current (0.25 pA at 5 V bias voltage), a typical responsivity of 0.103 A/W at 20 V, and a peak response wavelength at 290 nm. The fabricated devices held a high DUV to visible rejection ratio of >10³.     

Simulation of the Metal-Semiconductor-Metal photodetector based on InGaAs for the photodetection at the wavelength 1.55 μm

In this paper we present the simulation of Metal-Semiconductor-Metal photodetector (MSM-PD) of interdigitated planar structure based on InAlAs/InGaAs adapted for photodetection at the wavelength 1.55 μm. We use the theoretical models to plot the variations of the dark current, the photocurrent, the capacity, and the cut-off frequency of the photodetector as a function of bias voltage and the interelectrode distance. The obtained results show a very low dark current, mainly due to the introduction of a thin layer to increase the Schottky barrier based on In_0.52Al_0.48As in the epitaxial structure of component. The obtained photocurrent and cut-off frequencies are very appreciable, these latter are mainly limited by the transit time of the photo-generated carriers given the low component capacity obtained by simulation.     

Dark currents of GaAs/AlGaAs quantum-well infrared photodetectors

We study the dark current of the GaAs/AlGaAs quantum-well infrared photodetector (QWIP) by assuming a drift-diffusion carrier transport in the barriers where the electric fields are obtained by the current continuity condition and the self-consistent energy band structure. It has been shown that due to the current continuity condition, the dark currents across the QWIP devices are determined by the thermionic emission from the emitter to the multiple quantum well (MQW) region. The self-consistent calculation of the Schrödinger and Poisson equations shows a weak electric field in the barrier region connecting to the emitter (much smaller than the average field across the QWIP at low bias) due to the accumulation of carriers in the triangle quantum well formed at the emitter-MQW interface, which results in a very small dark current at low bias. The numerical results explain well our experimental observation.     

A 4×4 metal-semiconductor-metal rectangular deep-ultraviolet detector array of Ga2O3 photoconductor with high photo response

A 4$\times $4 beta-phase gallium oxide ($\beta $-Ga$_{2}$O$_{3}$) deep-ultraviolet (DUV) rectangular 10-fingers interdigital metal-semiconductor-metal (MSM) photodetector array of high photo responsivity is introduced. The Ga$_{2}$O$_{3}$ thin film is prepared through the metalorganic chemical vapor deposition technique, then used to construct the photodetector array via photolithography, lift-off, and ion beam sputtering methods. The one photodetector cell shows dark current of 1.94 pA, photo-to-dark current ratio of 6$\times $10$^{7}$, photo responsivity of 634.15 A$\cdot$W$^{-1}$, specific detectivity of 5.93$\times $10$^{11}$ cm$\cdot$Hz$^{1/2}\cdot$W$^{-1}$ (Jones), external quantum efficiency of 310000%, and linear dynamic region of 108.94 dB, indicating high performances for DUV photo detection. Furthermore, the 16-cell photodetector array displays uniform performances with decent deviation of 19.6% for photo responsivity.     

Analytical Simulation of an InAsSb Photovoltaic Detector for Mid-Infrared Applications

A generic model of a mid-infrared photodetector based on a narrow bandgap semiconductor has been developed. The model has been applied for analysis and simulation of an InAs_0.89Sb_0.11 photovoltaic detector for operation at room temperature in 2–5 μm wavelength region. The model takes into account the effect of tunneling and other components of dark current on the detectivity of the device by considering all the three dominant recombination mechanisms e.g., radiative, Shockley-Read-Hall and Auger recombination. The study revealed that the dark current of the photodetector under reverse bias is dominated by trap-assisted tunneling component of current and this causes the detectivity of the device to decrease at high reverse bias. It is further concluded that by operating the device at a suitable low reverse bias it is possible to improve the room-temperature detectivity significantly as compared to its value at zero bias.     

电极肖特基接触对有机光敏晶体管性能的影响

有机光敏晶体管是一种在有机场效应管结构中引入光控“栅极”的新型光探测器件,其光灵敏度、光响应度性能参数与源/漏电极和有源层的接触情况关系密切。本文通过真空蒸发法分别制备了采用金电极和铝电极的单层并五苯及酞菁铜有机光敏晶体管。研究了它们在黑暗和光照条件下的输出及转移特性。结果表明,高迁移率的并五苯有源层更适合搭配接触特性较好的金电极,该器件具有和铝电极器件相同高水平的光灵敏度~3×104,但其光响应度是铝电极器件的13倍;而低迁移率的酞菁铜薄膜较适合搭配能够和有源层形成肖特基接触的铝电极,有利于抑制暗电流、增强激子解离效率、提高光电流,进一步使器件在获得和金电极器件同数量级光响应度的同时,其光灵敏度是金电极器件的102倍。本文对光照下电极/有源层肖特基接触的能带变化做了理论分析,总结归纳了有机光敏晶体管电极材料和有源层材料的初步筛选规律。