GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

Reconfigurable CMOS with undoped silicon nanowire midgap Schottky-barrier FETs

In this paper we report on a newly developed multi-gate nanowire-field-effect device (NWFET) in which the transistor type (i.e. PMOS and NMOS) is freely selectable by the application of a control-voltage. This significantly adds to flexibility in design of integrated circuits and their fabrication, respectively. We will show, that the use of midgap Schottky-barrier source and drain contacts are the key enabler for this device concept to be functional. A fully functional freely configurable CMOS-NWFET inverter circuit is presented, demonstrating the capability of this SOI technology platform. All this makes the presented NWFET-technology suitable for the fabrication multi-purpose devices for many applications.     

金属-砷化镓研究

本文评述了金属-半导体接触的各种机理以及这个接触在半导体枝术中的实际应用。     

Surface effects in sem measurements of hole diffusion length in n-GaAs

In scanning-electron microscope injection measurements of hole diffusion lengths in n-type gallium arsenide Schottky barrier junctions the results obtained depend strongly on the surface treatment (exposure to air, H₂0, or HC1 treatments) after cleaving. The effect is attributed to band bending causing a p-region on the surface which allows collection of minority carriers produced far from the junction. Scanning of the semiconductor surface by the 25 keV electron beam for a few minutes prior to diffusion length measurements is found to remove these contamination effects and give reliable and consistent results.     

Effects of a a-Si:H layer on reducing the dark current of 1310 nm metal-germanium-metal photodetectors

Two approaches of hydrogenated-amorphous-silicon (a-Si:H), as Schottky-barrier height (SBH) enhancement and passivation layers, were investigated to suppress dark current of 1310 nm metal-germanium-metal photodetectors (MGM-PDs). Observations show that when a-Si:H is inserted between metal and Ge, the dark current is effectively reduced due to SBH enhancement, but similarly lowers photocurrent resulting from the blocking of a-Si:H. In contrast with a-Si:H acting as a passivation layer a very high photo-to-dark current ratio of 6530 is achieved with a high responsivity of 0.72 A/W, attributing to the defect centers on the Ge surface which are passivated. Such a result suggests that the a-Si:H passivation layer is a good candidate in fabricating high-quality 1310 nm MGM-PDs.     

太赫兹肖特基二极管噪声电压的理论研究

在太赫兹焦平面成像等系统中,GaAs肖特基二极管作为太赫兹检测的核心器件,其噪声特性直接影响太赫兹探测系统的灵敏度。讨论了GaAs肖特基二极管在不同直流偏压下加载给负载的热噪声电压、散粒噪声电压、总噪声电压,并给出了相应的解析解。同时,建模模拟了太赫兹混频前端,并利用谐波平衡法对理论公式进行了对比验证。对太赫兹像元与阵列芯片的噪声机理以及提高芯片的噪声性能研究,改善芯片噪声特性,从而提高太赫兹焦平面成像系统灵敏度具有重要意义和作用。     

High frequency performance of nano-scale ultra-thin-body Schottky-barrier n-MOSFETs

The high frequency performances of nano-scale ultra-thin-body (UTB) Schottky-barrier n-MOSFETs (SB-nMOSFETs) are investigated using 2D full-band self-consistent ensemble Monte Carlo method. The UTB SB-nMOSFET devices offer excellent RF performance with high values of f T and f max.The significant dependence of f T and f max on gate voltage and weak dependence on barrier height are demonstrated.Meanwhile,the significant dependence of g m and g ds on both gate voltage and SB height are shown. Moreover,the sca...     

一种肖特基势垒强型N-AlGaN基 MSM日盲紫外光电探测器

研制一种以薄的高阻AlGaN覆盖层作为肖特基势垒增强层的N?AlGaN基金属?半导体?金属（MSM）日盲紫外光电探测器。与无覆盖层的参考器件相比,覆盖高阻AlGaN层后探测器的暗电流大幅度减小。在5 V偏压下,覆盖高阻AlGaN层的光电探测器的暗电流为1.6 pA,响应度为22.5 mA/W,日盲紫外抑制比大于103,探测率为6.3×1010 cm·Hz1/2/W。     

Analytical modeling of trilayer graphene nanoribbon Schottky-barrier FET for high-speed switching applications

Recent development of trilayer graphene nanoribbon Schottky-barrier field-effect transistors (FETs) will be governed by transistor electrostatics and quantum effects that impose scaling limits like those of Si metal-oxide-semiconductor field-effect transistors. The current–voltage characteristic of a Schottky-barrier FET has been studied as a function of physical parameters such as effective mass, graphene nanoribbon length, gate insulator thickness, and electrical parameters such as Schottky barrier height and applied bias voltage. In this paper, the scaling behaviors of a Schottky-barrier FET using trilayer graphene nanoribbon are studied and analytically modeled. A novel analytical method is also presented for describing a switch in a Schottky-contact double-gate trilayer graphene nanoribbon FET. In the proposed model, different stacking arrangements of trilayer graphene nanoribbon are assumed as metal and semiconductor contacts to form a Schottky transistor. Based on this assumption, an analytical model and numerical solution of the junction current–voltage are presented in which the applied bias voltage and channel length dependence characteristics are highlighted. The model is then compared with other types of transistors. The developed model can assist in comprehending experiments involving graphene nanoribbon Schottky-barrier FETs. It is demonstrated that the proposed structure exhibits negligible short-channel effects, an improved on-current, realistic threshold voltage, and opposite subthreshold slope and meets the International Technology Roadmap for Semiconductors near-term guidelines. Finally, the results showed that there is a fast transient between on-off states. In other words, the suggested model can be used as a high-speed switch where the value of subthreshold slope is small and thus leads to less power consumption.     

W频段宽带倍频器

介绍了一个W频段宽带倍频器.采用反向并联二极管对结构实现宽带倍频.该倍频器输入为WR-28波导到微带过渡结构,输出为WR-10减高波导.在输入功率为5dBm时,在整个W频段输出功率为0.81±1.80dBm,二次谐波抑制度大于25dBc.该倍频器可把Ka频段的信号源扩展到W频段.