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Multiple enlarged growth of single crystal diamond by MPCVD with PCD-rimless top surface

Chinese Physics B 2019年第12期28卷 352-357页

作者： Ze-Yang Ren Jun Liu Kai Su jin-Feng zhang jin-cheng zhang Sheng-Rui Xu Yue Hao State Key Discipline Laboratory of Wide Band-Gap Semiconductor Technology School of MicroelectronicsXidian UniversityXi'an 710071China

We report the simultaneous enlarged growth of seven single crystal diamond(SCD) plates free from polycrystalline diamond(PCD) rim by using a microwave plasma chemical vapor deposition(MPCVD) system. Optical microscope and atomic force microscope(AFM) show the typical step-bunching SCD morphology at the center, edge, and corner of the samples. The most aggressively expanding sample shows a top surface area three times of that of the substrate. The effective surface expanding is attributed to the utilization of the diamond substrates with(001) side surfaces, the spacial isolation of them to allow the sample surface expanding, and the adoption of the reported pocket holder. Nearly constant temperature of the diamond surfaces is maintained during growth by only decreasing the sample height, and thus all the other growth parameters can be kept unchanged to achieve high quality SCDs. The SCDs have little stress as shown by the Raman spectra. The full width at half maximum(FWHM) data of both the Raman characteristic peak and(004) x-ray rocking curve of the samples are at the same level as those of the standard CVD SCD from Element Six Ltd. The nonuniformity of the sample thickness or growth rate is observed, and photoluminescence spectra show that the nitrogen impurity increases with increasing growth rate. It is found that the reduction of the methane ratio in the sources gas flow from 5% to 3% leads to decrease of the vertical growth rate and increase of the lateral growth rate. This is beneficial to expand the top surface and improve the thickness uniformity of the samples. At last, the convenience of the growth method transferring to massive production has also been demonstrated by the successful simultaneous enlarged growth of 14 SCD samples.

关键词： diamond chemical vapour deposition crystal growth expanded top surface polycrystalline diamond rimless

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Ohmic Contact at Al/TiO_2/n-Ge Interface with TiO_2 Deposited at Extremely Low Temperature

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Chinese Physics Letters 2018年第2期35卷 116-119页

作者： Yi zhang Huan Liu Gen-Quan Han Yan Liu jin-cheng zhang Yue Hao Key Laboratory of Wide Band-Gap Semiconductor Technology School of MicroelectronicsXidian University

TiO2deposited at extremely low temperature of 120°C by atomic layer deposition is inserted between metal and n-Ge to relieve the Fermi level pinning. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy indicate that the lower deposition temperature tends to effectively eliminate the formation of GeOxto reduce the tunneling resistance. Compared with TiO2deposited at higher temperature of 250°C,there are more oxygen vacancies in lower-temperature-deposited TiO2, which will dope TiO2contributing to the lower tunneling resistance. Al/TiO2/n-Ge metal-insulator-semiconductor diodes with 2 nm 120°C deposited TiO2achieves 2496 times of current density at-0.1 V compared with the device without the TiO2interface layer case, and is 8.85 times larger than that with 250°C deposited TiO2. Thus inserting extremely low temperature deposited TiO2to depin the Fermi level for n-Ge may be a better choice.

关键词： TiO Ohmic Contact at Al/TiO2/n-Ge Interface with TiO2 Deposited at Extremely Low Temperature Ge Al

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Temperature-Dependent Characteristics of GaN Schottky Barrier Diodes with TiN and Ni Anodes

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Chinese Physics Letters 2019年第5期36卷 54-58页

作者： Ting-Ting Wang Xiao Wang Xiao-Bo Li jin-cheng zhang jin-Ping Ao Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian UniversityXi’an 710071 Institute of Technology and Science Tokushima UniversityTokushima 770-8506Japan

The effect of temperature on the characteristics of gallium nitride (GaN) Schottky barrier diodes (SBDs) with TiN and Ni anodes is evaluated. With increasing the temperature from 25 to 175℃, reduction of the turn-on voltage and increase of the leakage current are observed for both GaN SBDs with TiN and Ni anodes. The performance after thermal treatment shows much better stability for SBDs with Ti N anode, while those with Ni anode change due to more interface states. It is found that the leakage currents of the GaN SBDs with TiN anode are in accord with the thermionic emission model whereas those of the GaN SBDs with Ni anode are much higher than the model. The Silvaco TCAD simulation results show that phonon-assisted tunneling caused by interface states may lead to the instability of electrical properties after thermal treatment, which dominates the leakage currents for GaN SBDs with Ni anode. Compared with GaN SBDs with Ni anode, GaN SBDs with TiN anode are beneficial to the application in microwave power rectification fields due to lower turn-on voltage and better thermal stability.

关键词： GaN SBD Temperature-Dependent Characteristics of GaN Schottky Barrier Diodes with TiN and Ni Anodes TiN Ni

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Inhibitive effect of IL-24 gene on CD133^+ laryngeal cancer cells

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Asian Pacific Journal of Tropical Medicine 2014年第11期7卷 867-872页

作者： jin-zhang cheng Dan Yu Hui zhang Chun-Shun jin Yan Liu Xue Zhao Xin-Meng Qi Xueshi-Bojie Liu Second Affiliated Hospital of Jilin University

Objective:To explore the inhihitive and apoptosis inductive effect of IL-24 genes on CD133^+laryngeal cancer cells in Hep-2 ***:Human peripheral blood monocytes were *** total RNA was extracted by using Trizol method and reverse transcripted into cDNA using RT-PCR *** P1 and P2 was designed for the amplification of human IL-24 *** confirmation of agarose gel electrophoresis tests,TA was cloned into pMD19-T simple *** Ⅰ and Xho Ⅰ double digesting human IL-24 and pIRES2-ZsGreen1 and eukaryotic expression vector were used to establish the pIRES2-ZsGreen1-hIL-24 vector,and detected by enzyme digestion and gene sequencing *** cytometry(FCM) was used to isolate CD133^+ cells from Hep-2 ***133^+ cells were transfected with pIRES2-ZsGreen1-hIL-24 through liposome *** detection,MTT and FCM were used to observe the effect of IL-24 gene on CD133^+ laryngeal cancer Hep-2 ***:Lipotin mediated transfection of recombinant pIRES2-ZsGreen1-hIL-24 plasmid into CD133^+ Hep-2 could expressed IL-24 gene in cells *** results showed that IL-24 transfected group was significantly suppressed compared to empty vector group and control group(P<0.05);FCM results showed that the apoptosis rate of experimental group increased significantly compared to empty vector group and control group(P<0.05).Conclusions:IL-24 gene expressions can inhibit proliferation of CD133^+laryngeal cells in Hep-2 line and promote their apoptosis.

关键词： IL-24 CD133 Laryngeal cancer Cancer stem cells Gene therapy

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Phonon Limited Electron Mobility in Germanium FinFETs:Fin Direction Dependence

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Chinese Physics Letters 2019年第2期36卷 54-58页

作者： Ying jing Gen-Quan Han Yan Liu jin-cheng zhang Yue Hao Key Laboratory of Wide Band-Gap Semiconductor Technology School of MicroelectronicsXidian University

We investigate the phonon limited electron mobility in germanium(Ge) fin field-effect transistors(FinFETs)with fin rotating within(001),(110),and(111)-oriented wafers. The coupled Schrodinger-Poisson equations are solved self-consistently to calculate the electronic structures for the two-dimensional electron gas, and Fermi's golden rule is used to calculate the phonon scattering rate. It is concluded that the intra-valley acoustic phonon scattering is the dominant mechanism limiting the electron mobility in Ge FinFETs. The phonon limited electron motilities are influenced by wafer orientation, channel direction, in thickness Wfin, and inversion charge density Ninv. With the fixed Wfin, fin directions of(110),(112) and(110) within(001),(110), and(111)-oriented wafers provide the maximum values of electron mobility. The optimized for mobility is also dependent on wafer orientation and channel direction. As Ninv, increases, phonon limited mobility degrades, which is attributed to electron repopulation from a higher mobility valley to a lower mobility valley as Ninv increases.

关键词： Phonon Limited Electron Mobility Fin Direction Dependence

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Effects of the flow rate of hydrogen on the growth of graphene

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 102-110页

作者： Yong-gui Shi Yue Hao Dong Wang jin-cheng zhang Peng zhang Xue-fang Shi Dang Han Zheng Chai jing-dong Yan School of Microelectronics Xidian University State Key Discipline Laboratory of Wide Band-Gap Semiconductors and Devices Xidian University School of Technical Physics Xidian University

Graphene samples with different morphologies were fabricated on the inside of copper enclosures by low pressure chemical vapor deposition and tuning the flow rate of hydrogen. It is found that the flow rate of hydrogen greatly influences the growth of graphene. Ther-modynamic analysis indicates that a higher flow rate of hydrogen is favorable to the formation of good quality graphene with regular mor-phology. However, the mass-transfer process of methane dominates the growth driving force. At very low pressure, mass-transfer proceeds by Knudsen diffusion, and the mass-transfer flux of methane decreases as the flow rate of hydrogen increases, leading to a decrease in the growth driving force. At a higher pressure, mass-transfer proceeds by Fick＇s diffusion, and the mass-transfer flux of methane is dominated by the gas velocity, whose variation determines the growth driving force variation of graphene.

关键词： graphene crystal growth morphology diffusion mass transfer chemical vapor deposition

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High-performance InAlGaN/GaN enhancement-mode MOS-HEMTs grown by pulsed metal organic chemical vapor deposition

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Chinese Physics B 2019年第1期28卷 634-638页

作者： Ya-Chao zhang Zhi-Zhe Wang Rui Guo Ge Liu Wei-Min Bao jin-cheng zhang Yue Hao State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology School of Microelectronics Xidian University China Electronic Product Reliability and Environmental Testing Research Institute School of Aerospace Science and Technology Xidian University

Pulsed metal organic chemical vapor deposition was employed to grow nearly polarization matched InAlGaN/GaN heterostructures. A relatively low sheet carrier density of 1.8×10^(12)cm^(-2), together with a high electron mobility of1229.5 cm^2/V·s, was obtained for the prepared heterostructures. The surface morphology of the heterostructures was also significantly improved, i.e., with a root mean square roughness of 0.29 nm in a 2 μm×2 μm scan area. In addition to the improved properties, the enhancement-mode metal–oxide–semiconductor high electron mobility transistors(MOSHEMTs) processed on the heterostructures not only exhibited a high threshold voltage(VTH) of 3.1 V, but also demonstrated a significantly enhanced drain output current density of 669 m A/mm. These values probably represent the largest values obtained from the InAlGaN based enhancement-mode devices to the best of our knowledge. This study strongly indicates that the InAlGaN/GaN heterostructures grown by pulsed metal organic chemical vapor deposition could be promising for the applications of novel nitride-based electronic devices.

关键词： InAlGaN enhancement-mode metal–oxide–semiconductor high electron mobility transistor threshold voltage

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Novel CMOS image sensor pixel to improve charge transfer speed and efficiency by overlapping gate and temporary storage diffusing node

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Chinese Physics B 2021年第1期30卷 593-599页

作者： Cui Yang Guo-Liang Peng Wei Mao Xue-Feng Zheng Chong Wang jin-cheng zhang Yue Hao School of Physics and Optoelectronic Engineering Xidian UniversityXi’an 710071China Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian UniversityXi’an 710071China

A novel CMOS image sensor(CIS) pinned photodiode(PPD) pixel, named as O-T pixel, is proposed and investigated by TCAD simulations. Compared with the conventional PPD pixel, the proposed pixel features the overlapping gate(OG)and the temporary storage diffusing(TSD) region, based on which the several-nanosecond-level charge transfer could be achieved and the complete charge transfer from the PPD to the floating node(FD) could be realized. And systematic analyses of the influence of the doping conditions of the proposed processes, the OG length, and the photodiode length on the transfer performances of the proposed pixel are conducted. Optimized simulation results show that the total charge transfer time could reach about 5.862 ns from the photodiode to the sensed node and the corresponding charge transfer efficiency could reach as high as 99.995% in the proposed pixel with 10 μm long photodiode and 2.22 μm long OG. These results demonstrate a great potential of the proposed pixel in high-speed applications.

关键词： CMOS image sensor charge transfer efficiency high-speed charge transfer pinned photodiode

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Semipolar(1122) and polar(0001) InGaN grown on sapphire substrate by using pulsed metal organic chemical vapor deposition

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Chinese Physics B 2017年第2期26卷 467-472页

作者： Sheng-Rui Xu Ying Zhao Ren-Yuan Jiang Teng Jiang Ze-Yang Ren jin-cheng zhang Yue Hao Key Laboratory of Wide Band-Gap Semiconductor Technology School of Microelectronics Xidian University Xi＇ an 710071 China

High indium semipolar（1122） and polar（0001） In Ga N layers each with a thickness of about 100 nm are realized simultaneously on sapphire substrates by pulsed metal organic chemical vapor deposition（MOCVD）. The morphology evolution, structural and optical characteristics are also studied. The indium content in the layer of the surface（1122）is larger than that of the surface（0001）, which is confirmed by reciprocal space map, photoluminescence spectrum and secondary ion mass spectrometer. Additionally, the（0001） surface with island-like morphology shows inhomogeneous indium incorporation, while the（1122） surface with a spiral-like morphology shows a better homogeneous In *** feature is also demonstrated by the monochromatic cathodoluminescence map.

关键词： semipolar GaN MOCVD

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Low power fluorine plasma effects on electrical reliability of AlGaN/GaN high electron mobility transistor

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Chinese Physics B 2017年第1期26卷 433-437页

作者： Ling Yang Xiao-Wei Zhou Xiao-Hua Ma Ling Lv Yan-Rong Cao jin-cheng zhang Yue Hao State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology Xidian University Xi＇an 710071 China School of Advanced Materials and Nanotechnology Xidian University Xi＇an 710071 China School of Microelectronics Xidian University Xi＇an 710071 China School of Mechano-Electronic Engineering Xidian University Xi＇an 710071 China

The new electrical degradation phenomenon of the AlGaN/GaN high electron mobility transistor（HEMT） treated by low power fluorine plasma is discovered. The saturated current, on-resistance, threshold voltage, gate leakage and breakdown voltage show that each experiences a significant change in a short time stress, and then keeps unchangeable. The migration phenomenon of fluorine ions is further validated by the electron redistribution and breakdown voltage enhancement after off-state stress. These results suggest that the low power fluorine implant ion stays in an unstable state. It causes the electrical properties of AlGaN/GaN HEMT to present early degradation. A new migration and degradation mechanism of the low power fluorine implant ion under the off-stress electrical stress is proposed. The low power fluorine ions would drift at the beginning of the off-state stress, and then accumulate between gate and drain nearby the gate side. Due to the strong electronegativity of fluorine, the accumulation of the front fluorine ions would prevent the subsequent fluorine ions from drifting, thereby alleviating further the degradation of AlGaN/GaN HEMT electrical properties.

关键词： AlGaN/GaN HEMT low plasma power fluorine implant ion early electrical reliability

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