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Investigation of surface morphology and ion activation of aluminium implanted 4H-SiC

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Science China(Technological Sciences) 2012年第12期55卷 3401-3404页

作者： SONG QingWen zhang YuMing zhang yimen TANG XiaoYan Key Luboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidiau UniversityXi'an 710071China

Multiple-energy aluminium （AI＋） implantation into 4H-SiC （0001） epilayer and activation anneal with a graphite encapsnlation layer were investigated in this paper. Measurements showed that the implanted Ak＋ box doping profile was formed and a high ion activation ratio of 78% was achieved by 40 rain annealing at 1600℃ using a horizontal chemical vapor deposition （CVD） reactor. The step bunching effect associated with the high temper：lture post implantation activation annealing （PIA） process was dramatically suppressed by using the graphite encapsulation layer. And a flat and smooth surface with a small average surface roughness （RMS） value of around 1.16 nm was achieved for the implanted 4H-SiC after the PIA process. It was demonstrated that this surface protection technique is a quite effective process for 4H-SiC power devices fabrication.

关键词： 4H-SiC Al+ implantation activation anneal surtaee morphology

Atomic layer deposited high-k Hf_xAl_(1-x)O as an alternative gate dielectric for 4H-SiC MIS based transistors

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Science China(Technological Sciences) 2012年第3期55卷 606-609页

作者： SONG QingWen zhang YuMing zhang yimen TANG XiaoYan JIA RenXu Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian UniversityXi'an 710071China

HfxAl(1-x)O film grown by atomic layer deposition(ALD) on n-type 4H-SiC(0001) epitaxial layer has been *** show that it has relatively high breakdown electric field of 16.4 MV/cm,high dielectric constant of 16.3 and low gate leakage current of 2.47×10-5 A/cm2 at E=5 MV/cm,which makes ALD HfxAl(1-x)O a great potential candidate gate dielectric for 4H-SiC MIS based transistors.

关键词： ALD HfxAl(1-x)O 4H-SiC MIS

4H-Si C monolithic Darlington transistors with slight current gain drop at high collector current density

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Science China(Technological Sciences) 2018年第8期61卷 1238-1243页

作者： YUAN Lei SONG QingWen TANG XiaoYan zhang HongPeng zhang yimeng YANG Fei GUO LiXin zhang yimen zhang YuMing Key Laboratory of Wide Band Gap Semiconductor Materials and Devices School of Microelectronics Xidian University State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute Co. Ltd. School of Physics and Optoelectronic Engineering Xidian University

Profit from high current gain features, 4 H-Si C power Darlington transistor has the capacity for handling high current transmission. In this paper, monolithic Darlington transistors were fabricated using a simultaneous formation process for both n-type(emitter) and p-type(base) ohmic contact. The isolated device shows current gain of 1061 and 823 with collector current density(JC) increasing from 200 to 800 A/cm2, exhibiting a slight current gain drop at high JC. By extracting the interface state density(Dit) between Si O2 and p-type 4 H-Si C, it is found that this advantage owes to the improvement of the shallow bulk minority carrier lifetime in base region. Furthermore, ISE-TCAD(technology computer aided design) simulation was carried out to study the relationship between base minority lifetime and the current gain, from which the total base minority lifetime is estimated to be 48 ns. The open base breakdown voltage(BVCEO) is 850 V at a leakage current of 2 μA due to the electric filed crowding at the isolation bottom between drive bipolar junction transistor(BJT) and output BJT. To solve this, non-isolated devices were also fabricated with improved BVCEOof 2370 V, indicating the superior potential of 4 H-Si C monolithic Darlington transistors for high power application, while the current gain is deceased to 420, which needs further improvement.

关键词： monolithic Darlington transistors Gummel characteristic lifetime improvement breakdown voltage

Characterization of the heteroepitaxial growth of 3C-SiC on Si during low pressure chemical vapor deposition

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Chinese Science Bulletin 2010年第27期55卷 3102-3106页

作者： CHEN Da zhang YuMing zhang yimen WANG YueHu JIA RenXu Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of Microelectronics Xidian University Xi'an 710071 China

3C-SiC heteroepitaxial layers were grown on Si substrates using a horizontal,hot-wall low pressure chemical vapor deposition *** crystal quality,surface morphology and thickness uniformity of the layers were characterized by X-ray diffraction,atomic force microcopy and Fourier transform infrared spectroscopy,*** of the epitaxial layer was determined to follow a three-dimensional island mode initially and then switch to a step-flow mode as the growth time increases.

关键词：低压化学气相沉积 SiC 生长特性 3C 傅里叶变换红外光谱化学气相沉积系统外延层生长原子力显微镜

Effects of proton radiation on field limiting ring edge terminations in 4H–SiC junction barrier Schottky diodes

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Science China(Technological Sciences) 2019年第7期62卷 1210-1216页

作者： SONG QingWen TANG XiaoYan HAN Chao YUAN Hao YANG Shuai He XiaoNing zhang yimeng zhang yimen zhang YuMing School of Microelectronics Xidian University Xi 'an 710071 China The State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology Xi'an 710071 China

In this study, the effects of high-energy proton radiation on the effectiveness of edge terminations using field limiting rings(FLRs) in 4 H–SiC junction barrier Schottky(JBS) diodes were examined in detail. The devices were irradiated using 5-MeV protons at fluences ranging from 5×10^12 cm^-2 to 5×10^14 cm^-2. Further, the reverse breakdown performances of the investigated devices were measured both before and after irradiation. Proton irradiation initially decreased the breakdown voltage(BV);subsequently, the BV was increased as the proton fluence increased. At a fluence of 5×10^13 cm^-2, the BV was reduced by approximately 18%, whereas it was reduced by approximately 5% at a higher proton fluence of 5×10^14 cm^-2. The related degradation mechanism that was associated with this phenomenon was also investigated using the numerical simulations of the current-voltage(I-V) and capacitance-voltage(C-V) characteristics of the device. The main contribution to the radiation-induced changes in BV originates from the variations of charge distribution at the SiO2/4 H–SiC interface and the reduction of the net carrier density in the drift region. Both the aforementioned variations affect the spread of the electric field in the FLR edge termination regions.

关键词： 4H-SiC power device edge termination radiation effects

Fabrication of a monolithic 4H-SiC junction barrier schottky diode with the capability of high current

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Science China(Technological Sciences) 2015年第8期58卷 1369-1374页

作者： SONG QingWen YUAN Hao HAN Chao zhang YuMing TANG XiaoYan zhang yimeng GUO Hui zhang yimen JIA RenXu WANG YueHu School of Advanced Materials and Nanotechnology Xidian University Key Laboratory of Wide Band Gap Semiconductor Materials and Devices Xidian University

There is a great interest in monolithic 4H-SiC Junction Barrier Schottky （JBS） diodes with the capability of a high forward current for industrial power applications. In this paper, we report large-area monolithic 4H-SiC JBS diodes fabricated on a 10 μm 4H-SiC epitaxial layer doped to 6×1015 cm-3. JBS diodes with an active area of 30 mm2 had a forward current of up to 330 A at a forward voltage of 5 V, which corresponds to a current density of 1100 A/cm2. A near ideal breakdown voltage of 1.6 kV was also achieved for a reverse current of up to 100 gA through the use of an optimum multiple floating guard rings （MFGR） termination, which is about 87.2% of the theoretical value. The differential specific-on resistance （RSP-ON） was meas- ured to be 3.3 mΩcm2, leading to a FOM （VB2/RSP-ON） value of 0.78 GW/cm2, which is very close to the theoretical limit of the tradeoff between the specific-on resistance and breakdown voltage for 4H-SiC unipolar devices.

关键词： 4H-SiC JBS current capability breakdown voltage

Study on the mechanism of perpendicular magnetic anisotropy in Ta/CoFeB/MgO system

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Journal of Semiconductors 2017年第6期38卷 14-17页

作者： Yongle Lou Yuming zhang Hui Guo Daqing Xu yimen zhang School of Microelectronics Xidian UniversityKey laboratory of Wide Band-Gap Semiconductor Materials and Devices School of Electrical and Control Engineering Xi'an University of Science and Technology

The mechanism of perpendicular magnetic anisotropy（PMA）in a MgO-based magnetic tunnel junction（MTJ）has been studied in this *** comparing the magnetic properties and elementary composition analysis for different CoFeB-based structures,such as Ta/CoFeB/MgO,Ta/CoFeB/Ta and Ru/CoFeB/MgO structures,it is found that a certain amount of Fe-oxide existing at the interface of CoFeB/MgO is helpful to enhance the PMA and the PMA is originated from the interface of CoFeB/*** addition,Ta film plays an important role to enhance the PMA in Ta/CoFeB/MgO structure.

关键词： perpendicular magnetic anisotropy MgO-based MTJ X-ray photoelectron spectroscopy Fe-oxide

Improved empirical DC I-V model for 4H-SiC MESFETs

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Science in China(Series F) 2008年第8期51卷 1184-1192页

作者： CAO QuanJun zhang yimen zhang YuMing LV HongLiang WANG YueHu TANG XiaoYan GUO Hui Key Lab of Education Ministry for Wide Band-Gap Semiconductor Materials and Devices Microelectronics Institute of Xidian University Xi'an 710071 China

A novel empirical large signal direct current （DC）Ⅰ-Ⅴ model is presented considering the high saturation voltage, high pinch-off voltage, and wide operational range of drain voltage for 4H-SiC MESFETs. A comparison of the presented model with Statz, Materka, Curtice-Cubic, and recently reported 4H-SiC MESFET large signal Ⅰ-Ⅴ models is made through the Levenberg-Marquardt method for fitting in nonlinear regression. The results show that the new model has the advantages of high accuracy, easily making initial value and robustness over other models. The more accurate results are obtained by the improved channel modulation and saturation voltage coefficient when the device is operated in the sub-threshold and near pinch-off region. In addition the new model can be implemented to CAD tools directly, using for design of 4H-SiC MESFET based RF＆MW circuit, particularly MMIC （microwave monolithic integrate circuit）.

关键词： 4H-SiC MESFET DC Ⅰ-Ⅴ characteristics empirical model Levenberg-Marquardt method nonlinear regression

Effects of growth temperature and metamorphic buffer on electron mobility of InAs film grown on Si substrate by molecular beam epitaxy

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Chinese Physics B 2019年第2期28卷 428-433页

作者： Jing zhang Hongliang Lv Haiqiao Ni Shizheng Yang Xiaoran Cui Zhichuan Niu yimen zhang Yuming zhang School of Microelectronics Xidian University and the State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology State Key Laboratory for Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences

The growth of the InAs film directly on the Si substrate deflected from the plane(100) at 4° towards(110) has been performed using a two-step procedure. The effect of the growth and annealing temperature on the electron mobility and surface topography has been investigated for a set of samples. The results show that the highest electron mobility is4640 cm^2/V·s in the sample, in which the 10-nm InAs nucleation layer is grown at a low temperature of 320 ℃ followed by ramping up to 560 ℃, and the nucleation layer was annealed for 15 min and the second layer of InAs is grown at 520 ℃.The influence of different buffer layers on the electron mobility of the samples has also been investigated, which shows that the highest electron mobility of 9222 cm^2/V·s at 300 K is obtained in the sample grown on a thick and linearly graded InGaAlAs metamorphic buffer layer deposited at 420 ℃.

关键词： InAs Si high electron mobility growth temperature InGaAlAs metamorphic buffer