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202.
Semipolar(1122) and polar(0001) InGaN grown on sapphire substrate by using pulsed metal organic chemical vapor deposition
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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 composition.This feature is also demonstrated by the monochromatic cathodoluminescence map. 相似文献
203.
The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology
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The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology has been investigated deeply. The fabricated 1-nH spiral inductor on SiC substrate demonstrates a self-resonant frequency of 51.6 GHz, with a peak Q-fact of 12.14 at 22.1 GHz. From the S-parameters measurements, the exponential decay phenomenon is observed for L, Q-factor, and SRF with the air-bridge height decreasing, and an analytic expression is concluded to exactly fit the measured data which can be used to predict the performance of the spiral inductor. All the coefficients in the formula have specific meaning. By means of establishing the lumped model, the parasitic coupling capacitance of the air-bridge has been extracted and presents the exponential decay with the air-bridge heights decreasing which indicates that this capacitor is directly related to the coupling effect of the air-bridge. Through the electromagnetic field distribution simulation, the details of the electric field around the air-bridge have been presented which demonstrate the formation and the variation principles of the coupling effect. 相似文献
204.
Reverse blocking characteristics and mechanisms in Schottky-drain AlGaN/GaN HEMT with a drain field plate and floating field plates
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In this paper, a novel Al Ga N/Ga N HEMT with a Schottky drain and a compound field plate(SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate(CFP) consists of a drain field plate(DFP) and several floating field plates(FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain(SD HEMT) and the HEMT with a Schottky drain and a DFP(SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT.Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in Al Ga N/Ga N HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs. 相似文献
205.
AZO-gated and Ni/Au-gated AlGaN/GaN HEMTs are fabricated successfully,and an excellent transparency of AZOgated electrode is achieved.After a negative gate bias stress acts on two kinds of the devices,their photoresponse characteristics are investigated by using laser sources with different wavelengths.The effect of photoresponse on AZO-gated electrode device is more obvious than on Ni/Au-gated electrodes device.The electrons are trapped in the AlGaN barrier of AZO-gated HEMT after it has experienced negative gate bias stress,and then the electrons can be excited effectively after it has been illuminated by the light with certain wavelengths.Furthermore,the trap state density D_T and the time constantτ_T of the AZO-gated Schottky contact are extracted by fitting the measured parallel conductance in a frequency range from10 kHz to 10 MHz.The constants of the trap range from about 0.35 μs to 20.35 μs,and the trap state density increased from1.93×l0~(13)eV 1·cm~2 at an energy of 0.33 eV to 3.07×10~(11) eV~1·cm~2 at an energy of 0.40 eV.Moreover,the capacitance and conductance measurements are used to characterize the trapping effects under different illumination conditions in AZO-gated HEMTs.Reduced deep trap states' density is confirmed under the illumination of short wavelength light. 相似文献
206.
The effects of gate length L_G on breakdown voltage VBRare investigated in AlGaN/GaN high-electron-mobility transistors(HEMTs) with L_G= 1 μm~20 μm. With the increase of L_G, VBRis first increased, and then saturated at LG= 3 μm. For the HEMT with L_G= 1 μm, breakdown voltage VBRis 117 V, and it can be enhanced to 148 V for the HEMT with L-_G= 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage.A similar suppression of the impact ionization exists in the HEMTs with LG 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with LG= 3 μm~20 μm, and their breakdown voltages are in a range of 140 V–156 V. 相似文献
207.
Electrical characteristics of SiGe-on-insulator nMOSFET and SiGe-silicon-on-aluminum nitride nMOSFET
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This paper investigates the electrical characteristics and temperature distribution of strained Si/SiGe n-type metal oxide semiconductor field effect transistor(nMOSFET) fabricated on silicon-on-aluminum nitride(SOAN) substrate.This novel structure is named SGSOAN nMOSFET.A comparative study of self-heating effect of nMOSFET fabricated on SGOI and SGSOAN is presented.Numerical results show that this novel SGSOAN structure can greatly eliminate excessive self-heating in devices,which gives a more promising application for silicon on insulator to work at high temperatures. 相似文献
208.
Degradation characteristics of PMOSFETs under negative bias
temperature--positive bias temperature--negative bias temperature
(NBT--PBT--NBT) stress conditions are investigated in this paper. It
is found that for all device parameters, the threshold voltage has
the largest shift under the first NBT stress condition. When the
polarity of gate voltage is changed to positive, the shift of device
parameters can be greatly recovered. However, this recovery is
unstable. The more severe degradation appears soon after
reapplication of NBT stress condition. The second NBT stress causes
in linear drain current to degrade greatly, which is different from
that of the first NBT stress. This more severe parameter shift
results from the wear out of silicon substrate and oxide interface
during the first NBT and PBT stress due to carrier
trapping/detrapping and hydrogen related species diffusion. 相似文献
209.
In the existing models of estimating the yield and critical area, the
defect outline is usually assumed to be circular, but the observed
real defect outlines are irregular in shape. In this paper,
estimation of the yield and critical area is made using the Monte
Carlo technique and the relationship between the errors of yield
estimated by circular defect and the rectangle degree of the defect
is analysed. The rectangular model of a real defect is presented, and
the yield model is provided correspondingly. The models take into
account an outline similar to that of an original defect, the
characteristics of two-dimensional distribution of defects, the
feature of a layout routing, and the character of yield estimation.
In order to make the models practicable, the critical area
computations related to rectangular defect and regular (vertical or
horizontal) routing are discussed. The critical areas associated with
rectangular defect and non-regular routing are developed also, based
on the mathematical morphology. The experimental results show that
the new yield model may predict the yield caused by real defects more
accurately than the circular model. It is significant that the yield
is accurately estimated using the proposed model for IC metals. 相似文献
210.
YAG:V2+激光材料晶格畸变及其EPR参量研究 总被引:6,自引:6,他引:0
利用Newman的晶场叠加模型,建立了晶体微观结构与电子顺磁共振(EPR)参量之间的定量关系.采用全组态完全对角化方法,对YAG:V2+晶体的局域晶格畸变及其EPR参量进行了系统的研究,结果表明:V2+离子掺入YAG晶体后,V2+离子的局域结构产生压缩三角晶格畸变,沿[111]晶轴方向V2+离子上方的三个O2-配体与下方的三个O2-配体均偏离[111]轴1.96°,从而成功地解释了YAG:V2+晶体的EPR参量.同时研究也表明,SS与SOO磁相互作用对EPR参量的贡献不可忽略. 相似文献