Amorphous-SiCBN-Based Metal–Semiconductor–Metal Photodetector for High-Temperature Applications

A photodetector (PD) with metal-semiconductor-metal (MSM) structure has been developed using an amorphous SiCBN film. The amorphous SiCBN film was deposited on the silicon substrate using reactive RF magnetron sputtering. The optoelectronic performance of the SiCBN MSM devices has been examined through photocurrent measurements. Temperature effect, with respect to photocurrent ratios, has been studied. The detector sensitivity factor, which is determined through the PD current ratio, was greater than five at room temperature. Furthermore, the device showed an excellent current sensitivity factor that is greater than two even at a higher temperature of 200 ^oC . The improved performance of the device at higher temperatures could open avenues for high-temperature PD applications.     

UV-Enhanced a-Si:H Metal–Semiconductor–Metal Photodetector

Planar metal–semiconductor–metal (MSM) photodetectors with very thin hydrogenated amorphous silicon (a-Si) films were fabricated for the detection of ultraviolet (UV) radiation. Since DNA and proteins strongly absorb UV radiation, these detectors find application in DNA and protein detection. The performance of top and bottom electrode MSM structures with aluminum electrodes is compared. The measured results include a responsivity of 150 mA/W and an external quantum efficiency of 74% at a wavelength of 260 nm for the top electrode configuration at a bias of 2 $hbox{V}/muhbox{m}$ and a 10- $muhbox{m}$ finger spacing.      

Ge–SiGe Quantum-Well Waveguide Photodetectors on Silicon for the Near-Infrared

We demonstrate near-infrared waveguide photodetectors using Ge-SiGe quantum wells epitaxially grown on a silicon substrate. The diodes exhibit a low dark current of 17.9 mA/cm² at 5-V reverse bias. The photodetectors are designed to work optimally at 1480 nm, where the external responsivity is 170 mA/W, which is mainly limited by the fiber-to-waveguide coupling loss. The 1480-nm wavelength matches the optimum wavelength for quantum-well electroabsorption modulators built on the same epitaxy, but these photodetectors also exhibit performance comparable to the demonstrated Ge-based detectors at longer wavelengths. At 1530 nm, we see open eye diagrams at 2.5-Gb/s operation and the external responsivity is as high as 66 mA/W. The technology is potentially integrable with the standard complementary metal-oxide-semiconductor process and offers an efficient solution for on-chip optical interconnects.     

Intrinsic Polarization of Self-Assembled Guanosine Supramolecules in GaN-Based Metal–Semiconductor–Metal Nano-Structures

The transport properties of self-assembled guanosine supramolecules (SAGS) confined within nanoscale metal electrodes on transparent GaN semiconductor substrates have been studied. The modified guanosine molecules have been used as self-assembled nanowires to realize nanoscale UV-Visible photodetectors with self-assembly length ranging from 30 to 450 nm. The ribbon-like guanosine supramolecules exhibit semiconductor properties and have polarization along its axis due to the strong intrinsic dipole moment of guanosine molecules. The charge transport through the SAGS wire with nanoscale metal-semiconductor-metal structure on passivated Ga-terminated GaN surface can be explained by Schottky type conductivity and near-surface-states. The intrinsic polarization in SAGS nano-wires changes the band-offset at the metal-semiconductor interface similar to semiconductor photodiodes.      

Dark-Current Suppression in Metal–Germanium–Metal Photodetectors Through Dopant-Segregation in NiGe—Schottky Barrier

We demonstrate, for the first time, the application of dopant-segregation (DS) technique in metal-germanium- metal photodetectors for dark-current suppression and high-speed performance. Low defect density and surface smooth epi-Ge (~300 nm) layer was selectively grown on patterned Si substrate using two-step epi-growth at 400degC/600degC combined with a thin (~10 nm) low-temperature Si/Si_0.8 Ge_0.2 buffer layer. NiGe with DS effectively modulates the Schottky barrier height and suppresses dark current to ~10 ^-7 A at -1 V bias (width/spacing: 30/2.5 mum). Under normal incidence illumination at 1.55 mum, the devices show photoresponsivity of 0.12 A/W. The 3 dB bandwidth under - 1 V bias is up to 6 GHz.     

Sensing Amorphous/Crystalline Silicon Surface Passivation by Attenuated Total Reflection Infrared Spectroscopy of Amorphous Silicon on Glass

Semiconductors - Attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy and effective lifetime measurements have been used to characterize amorphous/crystalline silicon...     

Metal‐Catalyzed Etching of Vertically Aligned Polysilicon and Amorphous Silicon Nanowire Arrays by Etching Direction Confinement

A systematic study of metal‐catalyzed etching of (100), (110), and (111) silicon substrates using gold catalysts with three varying geometrical characteristics: isolated nanoparticles, metal meshes with small hole spacings, and metal meshes with large hole spacings is carried out. It is shown that for both isolated metal catalyst nanoparticles and meshes with small hole spacings, etching proceeds in the crystallographically preferred <100> direction. However, the etching is confined to the single direction normal to the substrate surface when a catalyst meshes with large hole spacings is used. We have also demonstrated that the metal catalyzed etching method when used with metal mesh with large hole spacings can be extended to create arrays of polycrystalline and amorphous vertically aligned silicon nanowire by confining the etching to proceed in the normal direction to the substrate surface. The ability to pattern wires from polycrystalline and amorphous silicon thin films opens the possibility of making silicon nanowire array‐based devices on a much wider range of substrates.     

High‐Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self‐Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self‐assembled monolayer (SAM)‐based doping on the performance of WSe₂‐ and MoS₂‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p‐doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm² V^?1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^?1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^?1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^?1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6‐fold in the OTS/WSe₂ devices and ≈24.5‐fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air‐exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD‐based electronic/optoelectronic applications.     

一种采用BiCMOS工艺的SiGe HBT基区生长方法

为抑制SiGeHBT基区生长过程中岛状物生成,降低位错密度,基于渐变温度控制方法和图形外延技术,结合BiCMOS工艺,研发了在Si衬底上制备高质量Si1-xGex基区的外延生长方法。通过原子力显微镜(AFM)、扫描电子显微镜(SEM)、X射线双晶衍射(XRD)测试,显示所生长的Si1,Gex基区表面粗糙度为0.45nm,穿透位错密度是0.3×103～1.2×103cm-2。,在窗口边界与基区表面未发现位错堆积与岛状物。结果表明,该方法适宜生长高质量的SiGeHBT基区,可望应用于SiGeBiCMOS工艺中HBT的制备。     

Enhancing the Photoelectric Performance of Photodetectors Based on Metal Oxide Semiconductors by Charge‐Carrier Engineering

Semiconductor‐based photodetectors (PDs) convert light signals into electrical signals via the photoelectric effect, which involves the generation, separation, and transportation of the photoinduced charge carriers, as well as the extraction of these charge carriers to external circuits. Because of their specific electronic and optoelectronic properties, metal oxide semiconductors are widely used building blocks in photoelectric devices. However, the compromise between enhancing the photoresponse and reducing the rise/decay times limits the practical applications of PDs based on metal oxide semiconductors. As the behaviors of the charge carriers play important roles in the photoelectric conversion process of these PDs, researchers have proposed several strategies, including modification of light absorption, design of novel PD heterostructures, construction of specific geometries, and adoption of specific electrode configurations to modulate the charge‐carrier behaviors and improve the photoelectric performance of related PDs. This review aims to introduce and summarize the latest researches on enhancing the photoelectric performance of PDs based on metal oxide semiconductors via charge‐carrier engineering, and proposes possible opportunities and directions for the future developments of these PDs in the last section.     

Room‐Temperature Electrochemical Conversion of Metal–Organic Frameworks into Porous Amorphous Metal Sulfides with Tailored Composition and Hydrogen Evolution Activity

The conversion of metal–organic frameworks (MOFs) into inorganic nanomaterials is considered as an attractive means to produce highly efficient electrocatalysts for alternative‐energy related applications. Yet, traditionally employed MOF‐conversion conditions (e.g., pyrolysis) commonly involve multiple complex high‐temperature reaction processes, which often make it challenging to control the composition, pore structure, and active‐sites of the MOF‐derived catalysts. Herein, a general, simple, room‐temperature method is presented for a controlled electrochemical conversion of MOF (EC‐MOF) films into porous, amorphous metal sulfides (a‐MS_x). Detailed X‐ray photoelectron spectroscopy analysis and control over independent EC‐MOF parameters (e.g., scan‐rate and potential window) enable to gain insights on the MOF‐conversion mechanisms, and in turn to fine‐tune the porosity and composition of the obtained MS_x. As a result, a highly active amorphous cobalt sulfide (a‐CoS_x) electrocatalyst can be designed for hydrogen evolution reaction in neutral pH. Furthermore, the adjustable nature of the EC‐MOF method allows to draw conclusions about the correlation between the concentration of catalytically active species ( sites) and the hydrogen evolution properties of the a‐CoS_x. Given the method's generality and the diversity of available MOF structures, EC‐MOF provides a compelling platform for a rational design of a wide variety of active electrocatalytic materials.     

High-Performance Al–Sn–Zn–In–O Thin-Film Transistors: Impact of Passivation Layer on Device Stability

We fabricated high-performance thin-film transistors (TFTs) with an amorphous-Al–Sn–Zn–In–O (a-AT-ZIO) channel deposited by cosputtering using a dual Al–Zn–O and In–Sn–O target. The fabricated AT-ZIO TFTs, which feature a bottom-gate and bottom-contact configuration, exhibited a high field-effect mobility of 31.9 $ hbox{cm}^{2}/hbox{V}cdothbox{s}$, an excellent subthreshold gate swing of 0.07 V/decade, and a high $I_{{rm on}/{rm off}}$ ratio of $≫hbox{10}^{9}$, even below the process temperature of 250 $^{circ}hbox{C}$. In addition, we demonstrated that the temperature and bias-induced stability of the bottom-gate TFT structure can significantly be improved by adopting a suitable passivation layer of atomic-layer-deposition-derived $hbox{Al}_{2} hbox{O}_{3}$ thin film.      

Electrostatic Reliability Characteristics of GaN Flip-Chip Power Light-Emitting Diodes With Metal–Oxide–Silicon Submount

The electrostatic reliability characteristics of gallium nitride flip-chip (FC) power light-emitting diodes (PLEDs) with metal-oxide-silicon (MOS) submount are investigated for the first time. The electrostatic damage reliability of the reported diode submount and that of our proposed simple structure MOS submount are fabricated and compared. Their corresponding electrostatic protection capabilities are increased from 200 V (conventional PLED) to 500 V (FC-PLED on diode submount), to 500 V (FC-PLED on MOS submount with a SiO₂ thickness of 297 A?), and even to a value as high as 1000 V (FC-PLED at a SiO₂ thickness of 167 A?), which are much higher than the PLED industrial test value of 150 V at -5 V/-10 ? A criterion and are also much more robust than the previous academic reports.     

High-Permittivity Dielectric Stack on Gallium Nitride Formed by Silane Surface Passivation and Metal–Organic Chemical Vapor Deposition

We report the first demonstration of an in situ surface-passivation technology for a GaN substrate using vacuum anneal (VA) and silane ( SiH₄) treatment in a metal-organic chemical vapor deposition multichamber tool. Excellent electrical properties were obtained for TaN/HfAlO/GaN capacitors. Interface state density D_it was measured from midgap to near-conduction-band edge (E_C) using the conductance method at high temperatures, and the lowest D_it of 1 × 10¹¹ cm^-2 · eV^-1 at the midgap was achieved. Multiple frequency capacitance-voltage (C-V) measurement (10, 400, and 500 kHz) showed little frequency dispersion. Furthermore, the TaN/HfAlO/GaN stack was studied using high-resolution transmission electron microscopy, and the effectiveness of passivation using VA and SiH₄ was evaluated using high-resolution X-ray photoelectron spectroscopy. The method reported here effectively removes the native oxide and passivates the GaN surface during the high-k dielectric-deposition process.     

An Effective Approach to Achieve a Spin Gapless Semiconductor–Half‐Metal–Metal Transition in Zigzag Graphene Nanoribbons: Attaching A Floating Induced Dipole Field via π–π Interactions

Under first‐principles computations, a simple strategy is identified to modulate the electronic and magnetic properties of zigzag graphene nanoribbons (zGNRs). This strategy takes advantage of the effect of the floating dipole field attached to zGNRs via π–π interactions. This dipole field is induced by the acceptor/donor functional groups, which decorate the ladder‐structure polydiacetylene derivatives with an excellent delocalized π‐conjugated backbone. By tuning the acceptor/donor groups, –C≡C– number, and zGNR width, greatly enriched electronic and magnetic properties, e.g., spin gapless semiconducting, half‐metallic, and metallic behaviors, with the antiferromagnetic?ferromagnetic conversion can be achieved in zGNRs with perfect, 57‐reconstructed, and partially hydrogenated edge patterns.     

High-Detectivity Nitride-Based MSM Photodetectors on InGaN–GaN Multiquantum Well With the Unactivated Mg-Doped GaN Layer

InGaN-GaN multiquantum-well (MQW) metal-semiconductor-metal (MSM) photodetectors (PDs) with the unactivated Mg-doped GaN cap layer were successfully fabricated. It was found that we could achieve a dark current by as much as six orders of magnitude smaller by inserting the unactivated Mg-doped GaN cap layer. For MSM photodetectors with the unactivated Mg-doped GaN cap layer, the responsivity at 380 nm was found to be 0.372 A/W when the device was biased at 5 V. The UV-to-visible rejection ratio was also estimated to be around 1.96 times 10³ for the photodetectors with the unactivated Mg-doped GaN cap layer. With a 5-V applied bias, we found that minimum noise equivalent power and normalized detectivity of our PDs were 4.09 times 10^-14 W and 1.18 times 10¹³ cmmiddotHz^0.5W^-1, respectively. Briefly, incorporating the unactivated Mg-doped GaN layer into the PDs beneficially brings about the suppression of dark current and a corresponding improvement in the device characteristics.     

YON界面钝化层改善HfO2/Ge界面特性的研究

本文采用YON界面钝化层来改善HfO₂栅介质Ge metal-oxide-semiconductor（MOS）器件的界面质量和电特性.比较研究了两种不同的YON制备方法：在Ar+N₂氛围中溅射Y₂O₃靶直接淀积获得以及先在Ar+N₂氛围中溅射Y靶淀积YN再于含氧氛围中退火形成YON.实验结果及XPS的分析表明,后者可以利用YN在退火过程中先于Ge表面吸收从界面扩散的O而氧化,从而阻挡了O扩散到达Ge表面,更有效抑制了界面处Ge氧化物的形成,获得了更优良的界面特性和电特性：较小的CET（1.66 nm）,较大的k值（18.8）,较低的界面态密度（7.79×10¹¹ eV^-1cm^-2）和等效氧化物电荷密度（-4.83×10¹² cm^-2）,低的栅极漏电流（3.40×10^-4 A/cm²@V_g=V_fb+1 V）以及好的高场应力可靠性.     

On the Lateral Recrystallization of Amorphous Silicon Nanostructures Using Nickel Silicide

Semiconductors - The method of metal-induced lateral recrystallization is an urgent research task for manufacturing integrated circuits of multilevel architecture, sensitive elements of sensors, as...     

AlGaN/GaN Metal–Oxide–Semiconductor High-Electron Mobility Transistors Using Oxide Insulator Grown by Photoelectrochemical Oxidation Method

A photoelectrochemical oxidation method was used to directly grow oxide layer on AlGaN surface. The annealed oxide layer exhibited beta-Ga₂O₃ and alpha-Al₂O₃ crystalline phases. Using a photoassisted capacitance-voltage method, a low average interface-state density of 5.1 times 10¹¹ cm^-2. eV^-1 was estimated. The directly grown oxide layer was used as gate insulator for AlGaN/GaN MOS high-electron mobility transistors (MOS-HEMTs). The threshold voltage of MOS-HEMT devices is -5 V. The gate leakage currents are 50 and 2 pA at forward gate bias of VGS = 10 V and reverse gate bias of V_GS = -10 V, respectively. The maximum value of g_m is 50 mS/mm of VGs biased at -2.09 V.     

Efficient and Flexible Thin Film Amorphous Silicon Solar Cells on Nanotextured Polymer Substrate Using Sol–gel Based Nanoimprinting Method

The mechanical flexibility of substrates and controllable nanostructures are two major considerations in designing high‐performance, flexible thin‐film solar cells. In this work, we proposed an approach to realize highly ordered metal oxide nanopatterns on polyimide (PI) substrate based on the sol‐gel chemistry and soft thermal nanoimprinting lithography. Thin‐film amorphous silicon (a‐Si:H) solar cells were subsequently constructed on the patterned PI flexible substrates. The periodic nanopatterns delivered broadband‐enhanced light absorption and quantum efficiency, as well as the eventual power conversion efficiency (PCE). The nanotextures also benefit for the device yield and mechanical flexibility, which experienced little efficiency drop even after 100,000 bending cycles. In addition, flexible, transparent nanocone films, obtained by a template process, were attached onto the patterned PI solar cells, serving as top anti‐reflection layers. The PCE performance with these dual‐interfacial patterns rose up to 8.17%, that is, it improved by 48.5% over the planar device. Although the work was conducted on a‐Si:H material, our proposed scheme can be extended to a variety of active materials for different optoelectronic applications.