自供能Bi2O2Se/TiO2异质结紫外探测器的制备与光电探测性能

采用一步水热法合成了不同质量分数的Bi₂O₂Se/TiO₂异质结构,对其进行了X射线衍射、扫描电子显微镜和透射电子显微镜表征,并基于Bi₂O₂Se/TiO₂异质结制备了紫外探测器。实验结果表明：在365 nm紫外光的照射下,Bi₂O₂Se的质量分数为60%时,Bi₂O₂Se/TiO₂异质结探测器的光电探测性能最好,光电流高于Bi₂O₂Se探测器,是TiO₂探测器的7倍;响应时间约为30 ms,是TiO₂探测器的1/6。Bi₂O₂Se/TiO₂异质结探测器的响应度和探测率分别为10^-3A/W、1.08×10⁷cm·Hz^1/2/W,均比...     

高性能石墨烯/硅纳米线阵列异质结光探测器

设计了基于石墨烯/硅纳米线阵列异质结的高灵敏度自驱动光探测器。该探测器中的纳米线阵列为直径约为100 nm的周期性结构,表面纳米结构的光捕获效应可以有效地抑制入射光的反射,增加了有效光照面积,增强了异质结的吸收,从而提高了器件的光电检测性能。实验制备出的异质结在±3 V偏压下表现出明显的电流整流特性,整流比为6.93×10⁵。此外,由于纳米线阵列的光捕获效应增强了探测器在紫外到近红外的吸收,所以该探测器的探测范围可以从紫外到近红外光。在入射波长810 nm、光强为90μW/cm²的光照下,光探测器的光电流响应度可以达到0.56 A·W^-1,光电压响应度达1.24×10⁶ V·W^-1,探测率为1.18×10¹² Jones。更重要的是,该器件具有30/32μs的快速升/降响应速度。     

石墨烯/硅异质结光电导型探测器光电响应及噪声

设计并制备了石墨烯/硅异质结光电导型光电探测器,重点分析了光电响应与噪声性能。相比纯硅光电导探测器,石墨烯/硅异质结光电导探测器对635 nm波长激光的净光电流从20μA提升至260μA,与此同时,其1 Hz噪声幅值从3.2×10^-17 A²/Hz增加至2.1×10^-16 A²/Hz。进一步比较两种探测器的相对信噪比(净光电流/1 Hz噪声幅值),发现石墨烯/硅异质结探测器的相对信噪比(1.2×10¹⁸)优于纯硅探测器的(6.3×10¹⁷)。此外,探究了石墨烯条带尺寸对于光电响应及噪声的影响,发现随着石墨烯条带长度的增加,探测器的光电响应与噪声呈下降趋势;随着石墨烯条带宽度的增加,探测器的光电响应与噪声呈上升趋势。进一步比较了不同石墨烯条带长宽比探测器的净光电流与相对信噪比,发现净光电流随着长宽比的增大而减小,而相对信噪比随着长宽比的增大而增加。此外,通过沉积Al₂O₃对探测器的噪声进行了抑制。最后,利用栅压调制...     

垂直型g-C3N4/p++-Si异质结器件的光电性能

通过旋涂法制备垂直型的g-C₃N₄/p⁺⁺-Si异质结器件,研究该异质结器件的光电特性,探索其在可见和紫外光区的光电响应规律。该器件在零偏压和反偏压下均有明显的光电响应。在-1 V偏压下器件响应度为1.52 mA/W(激光波长532 nm,光强3.82 mW/mm²),响应时间约为0.94 s,光电流开关比为1.03×10³。相比于g-C₃N₄器件,g-C₃N₄/p⁺⁺-Si异质结器件具有更高的光电灵敏度。经过分析,其光电性能的提高是由于g-C₃N₄与Si之间形成了高质量的内建电场,该内建电场有效分离了g-C₃N₄中具有高结合能的激子,从而获得高的光生电流。特别是该器件在零偏压条件下的光电流开关比仍然可达10³以上,响应速度为0.5 s,表明g-C₃N₄/p⁺⁺-Si异质结器件在自供电低噪声光电探测器领域具有很好的应用前景。     

基于低温ALD氧化锌/钙钛矿复合膜的光电探测器

以原子层低温沉积技术(ALD)制备的氧化锌(ZnO)作为薄膜晶体管载流子传输层,将其与光电敏感性极高的CsPbBrI₂全无机钙钛矿薄膜复合进一步研制出光电晶体管用于光电探测。氧化锌薄膜晶体管可在150℃低温条件下制备且无需高温退火,同时,CsPbBrI₂钙钛矿薄膜也可以在低温工艺下制备。结果显示,CsPbBrI₂/ZnO光电探测器表现出较好的性能,可对365 nm至600 nm波长的光辐射有光响应。在500 nm波长的光照射下,最大响应度和探测率分别可达2×10³A/W和3×10¹⁴Jones。CsPbBrI₂/ZnO光电晶体管的瞬态响应显示出250 ms的上升时间和200 ms的下降时间,并且在长时间测量后瞬态行为保持不变。     

基于 InSe/MoTe2 异质结构的超灵敏宽光谱光电探测器

基于光栅效应的二维材料垂直结构可实现高灵敏度和宽光谱光探测器。本文报告了一种基于硒化铟（InSe）/二碲化钼（MoTe₂）垂直异质结构的高灵敏度光电探测器,该探测器在 365~965 nm 波长范围内具有出色的宽光谱探测能力。顶层的InSe用作调节沟道电流的光栅层,MoTe₂ 则用作传输层。通过结合两种材料的优势,该光电探测器的响应时间为 21.6 ms,比探测率在365 nm光照下可以达到1.05×10¹³ Jones,在965nm光照下也可达到10⁹ Jones数量级。外量子效率可达 1.03×10⁵%,显示出强大的光电转换能力。     

石墨烯MIS结宽光谱光电特性的研究

Ge基光电探测器具有独特的通信带宽响应特性和良好的CMOS工艺兼容性,在光电探测方面具有广阔的应用前景。但目前商用探测器的响应波段普遍局限在某一波段,难以满足多波段融合、小型化的探测需求。因此,通过在多层石墨烯和N型Ge之间引入薄的SiO2界面层,制备了基于石墨烯金属-绝缘层-半导体(MIS)结的光电探测器,分析了SiO₂的厚度以及石墨烯层数对MIS结器件性能的影响,并测试了器件的光谱响应范围、电流-电压曲线、响应度、开关比等光电特性。结果表明,该器件在254～2200 nm波段内均有响应,在980 nm处的响应度和开关比达到峰值,分别为78.36 mA/W和1.74×10³,上升时间和下降时间分别为1 ms和3 ms。     

基于碳管/石墨烯/GaAs双异质结自驱动的近红外光电探测器

基于单壁碳纳米管(SWCNT)/单层石墨烯/GaAs双异质结结构构筑了自驱动近红外光电探测器,利用GaAs优异的光电特性和石墨烯的高载流子迁移率特点,该光电探测器在无偏压情况下光电响应率可达393.8mA/W,比探测率达到6.48×1011 Jones,开关比为103。而且,利用半导体性SWCNT对近红外光子的高吸收特性以及SWCNT/石墨烯异质结对SWCNT产生光生载流子进行有效分离,使得该双异质结光电器件的光谱响应可拓展至1 064nm,突破了GaAs自身的响应极限860nm。     

二硫化锡薄膜场效应晶体管的可见光探测特性

采用化学气相输运(CVT)法和微机械剥离技术制备了SnS₂薄膜,使用Au电极作为源、漏电极,n型重掺杂Si作为栅极,制备了基于SnS₂薄膜的背栅型场效应晶体管(FET),并研究了其电学特性和可见光探测特性。结果表明,制备的SnS₂薄膜具有良好的结晶度,SnS₂薄膜背栅型FET具备良好的栅压调控特性。器件对波长为405 nm的蓝紫光表现出明显的光响应,光响应度高达456.82 A·W^-1,外量子效率为1.40×10⁵%,比探测率为7.12×10¹²Jones,并且具有较快的光响应速度,上升和下降响应时间分别为1 ms和0.5 ms。器件的光探测性能受栅压调控,当栅压为40 V时,器件的光响应度可达730 A·W^-1。     

高性能石墨烯/金字塔硅异质结近红外光探测器

石墨烯具有优异的光学性质和电学性质，在快速宽光谱光电探测方面有极大的潜力。本文设计并制备一种高性能石墨烯/n型金字塔硅异质结近红外光探测器。高质量石墨烯是采用化学气相沉积法制备的，通过湿法转移将其转移到n型金字塔硅表面，从而获得具有垂直结构的石墨烯/金字塔硅异质结器件。测试结果表明，在无光照条件下，器件的整流比达到了6.9×10⁵;在970 nm近红外光的照射下，电流开关比高达5.3×10⁴,电流响应度、外量子效率、光电压响应度和比探测率分别可达577.6 mA·W^-1、73.97%、1.26×10⁶V·W^-1和4.92×10¹²Jones。此外，器件具有快的响应速度，上升和下降时间分别为22μs和14.5μs。最后，还对器件稳定性进行研究，在空气环境中放置3个月后，光电流基本没有衰减，表明了器件具有优异的空气稳定性。     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

The C-V-f and G/ω-V-f characteristics of Al/SiO2/p-Si (MIS) structures

The frequency dependence of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the Al/SiO₂/p-Si metal-insulator-semiconductor (MIS) structures has been investigated taking into account the effect of the series resistance (R_s) and interface states (N_ss) at room temperature. The C-V and G/ω-V measurements have been carried out in the frequency range of 1 kHz to 1 MHz. The frequency dispersion in capacitance and conductance can be interpreted only in terms of interface states and series resistance. The N_ss can follow the ac signal and yield an excess capacitance especially at low frequencies. In low frequencies, the values of measured C and G/ω decrease in depletion and accumulation regions with increasing frequencies due to a continuous density distribution of interface states. The C-V plots exhibit anomalous peaks due to the N_ss and R_s effect. It has been experimentally determined that the peak positions in the C-V plot shift towards lower voltages and the peak value of the capacitance decreases with increasing frequency. The effect of series resistance on the capacitance is found appreciable at higher frequencies due to the interface state capacitance decreasing with increasing frequency. In addition, the high-frequency capacitance (C_m) and conductance (G_m/ω) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance. Experimental results show that the locations of N_ss and R_s have a significant effect on electrical characteristics of MIS structures.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Lanthanum diffusion in the TiN/LaOx/HfSiO/SiO2/Si stack

Band edge Complementary Metal Oxide Semiconductor (CMOS) devices are obtained by insertion of a thin LaO_x layer between the high-k (HfSiO) and metal gate (TiN). High temperature post deposition anneal induces Lanthanum diffusion across the HfSiO towards the SiO₂ interfacial layer, as shown by Time of Flight Secondary Ions Mass Spectroscopy (ToF-SIMS) and Atom Probe Tomography (APT). Fourier Transform Infrared Spectroscopy in Attenuated Total Reflexion mode (ATR-FTIR) shows the formation of La-O-Si bonds at the high-k/SiO₂ interface. Soft X-ray Photoelectron Spectroscopy (S-XPS) is performed after partial removal of the TiN gate. Results confirm La diffusion and changes in the La chemical environment.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.