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1.
Theoretical investigation of incomplete ionization of dopants in uniform and ion-implanted 4H-SiC MESFETs
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The effects of incomplete ionization of nitrogen in 4H-SiC have
been investigated. Poisson's equation is numerically analysed by
considering the effects of Poole--Frenkel, and the effects of
the potential on $N^+_\dd$ (the concentration of ionized donors)
and $n$ (the concentration of electrons). The pinch-off voltages
of the uniform and the ion-implanted channels of 4H-SiC
metal-semiconductor field-effect transistors (MESFETs) and
the capacitance of the gate are given at different temperatures.
Both the Poole--Frenkel effect and the potential have influence on
the pinch-off voltage $V_{\rm p}$ of 4H-SiC MESFETs. Although the
$C$-$V$ characteristics of the ion-implanted and the uniform channel of
4H-SiC MESFETs have a clear distinction, the effects of incomplete
ionization on the $C$-$V$ characteristics are not significant. 相似文献
2.
A thermal model of 4H-SiC MESFET is developed based on the
temperature dependences of material parameters and three-region $I-V$
model. The static current characteristics of 4H-SiC MESFET have been
obtained with the consideration of the self-heating effect on related
parameters including electron mobility, saturation velocity and
thermal conductivity. High voltage performances are analysed using
equivalent thermal conductivity model. Using the physical-based
simulations, we studied the dependence of self-heating temperature on
the thickness and doping of substrate. The obtained results can be
used for optimization of the thermal design of the SiC-based
high-power field effect transistors. 相似文献
3.
Hongliang Lu Yimen Zhang Yuming Zhang Yong Che Quanjun Cao Shaojin Zheng 《Applied Physics A: Materials Science & Processing》2008,91(2):287-290
In order to accurately and simply extract the trapping parameters in SiC metal semiconductor field effect transistors (MESFETs)
a method is proposed based on device dc and ac small-signal models. By combining modeling techniques, material physics, and
measured device characteristics, we are able to estimate the important information about the trap property and heat flow in
4H-SiC material and their influences on performance of MESFET devices, including gate lag, frequency-related dispersion, and
the self-heating effect. Simulations indicate that the gate lag is due to the traps located at the channel/buffer interface
and the transition frequency is up to ∼ MHz at 600 K.
PACS 72.15.Jf; 72.20.Jv; 72.15.Eb 相似文献
4.
5.
Improved performance of 4H-SiC metal-semiconductor field-effect transistors with step p-buffer layer
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An improved 4H-SiC metal-semiconductor field-effect transistors (MESFETs) with step p-buffer layer is proposed, and the static and dynamic electrical performances are analysed in this paper. A step p-buffer layer has been applied not only to increase the channel current, but also to improve the transconductance. This is due to the fact that the variation in p-buffer layer depth leads to the decrease in parasitic series resistance resulting from the change in the active channel thickness and modulation in the electric field distribution inside the channel. Detailed numerical simulations demonstrate that the saturation drain current and the maximum theoretical output power density of the proposed structure are about 30% and 37% larger than those of the conventional structure. The cut-off frequency and the maximum oscillation frequency of the proposed MESFETs are 14.5 and 62 GHz, respectively, which are higher than that of the conventional structure. Therefore, the 4H-SiC MESFETs with step p-buffer layer have superior direct-current and radio-frequency performances compared to the similar devices based on the conventional structure. 相似文献
6.
Experimental and numerical analysis of the multi-recessed gate structure for microwave silicon carbide power MESFETs
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This paper reports that multi-recessed gate 4H-SiC MESFETs
(metal semiconductor filed effect transistors) with a gate periphery
of 5-mm are fabricated and characterized. The multi-recessed region
under the gate terminal is applied to improve the gate--drain
breakdown voltage and to alleviate the trapping induced
instabilities by moving the current path away from the surface of
the device. The experimental results demonstrate that microwave
output power density, power gain and power-added efficiency for
multi-finger 5-mm gate periphery SiC MESFETs with multi-recessed
gate structure are about 29%, 1.1dB and 7% higher than those
of conventional devices fabricated in this work using the same
process. 相似文献
7.
Mohamed Kameche Mohamed Feham 《International Journal of Infrared and Millimeter Waves》2006,27(5):687-705
Simple techniques for determining the broadband small signal equivalent circuit (SSEC) of MESFETs are presented in this paper.
The intrinsic elements are calculated using two-dimensional method from the Y parameters, which are obtained from the Fourier
analysis of the device transient response to voltage-step perturbations at the drain and gate electrodes. Whereas, the parasitic
external elements are determined by simple approximations used in transmission line modeling. In addition, a new technique
is also proposed to determine the source and drain series resistances. A comparison of the SSEC of three different MESFETs
technologies shows that the MESFETs on GaN and 4H-SiC are suitable for high power applications. The method used to determine
the intrinsic elements is validated with simulated data obtained by Monte Carlo method. 相似文献
8.
Model and analysis of drain induced barrier lowering effect for 4H--SiC metal semiconductor field effect transistor
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Based on an analytical solution of the two-dimensional Poisson
equation in the subthreshold region, this paper investigates the
behavior of DIBL (drain induced barrier lowering) effect for short
channel 4H--SiC metal semiconductor field effect transistors
(MESFETs). An accurate analytical model of threshold voltage shift
for the asymmetric short channel 4H--SiC MESFET is presented and
thus verified. According to the presented model, it analyses the
threshold voltage for short channel device on the L/a (channel
length/channel depth) ratio, drain applied voltage VDS and
channel doping concentration ND, thus providing a good basis
for the design and modelling of short channel 4H--SiC MESFETs device. 相似文献
9.
The ohmic contacts of 4H-SiC are fabricated on nitrogen ion implanted layers made by performing
box-like-profile implantation three and four times. Implantation parameters such as the standard deviation σ and the projection range Rp are calculated by the Monte Carlo simulator TRIM. Ni/Cr ohmic contacts on Si-face 4H-SiC implantation layers are measured by transfer length methods (TLMs). The results show that the values of sheet resistance Rsh are 30~kΩ /□ and 4.9~kΩ/□ and the values of specific contact resistance ρc of ohmic contacts are 7.1× 10-4Ω.cm2 and 9.5× 10-5Ω.cm2 for the implanted layers with
implantation performed three and four times respectively. 相似文献
10.
Ion-implantation layers are fabricated by multiple
nitrogen ion-implantations (3 times for sample A and 4 times for
sample B) into a p-type 4H-SiC epitaxial layer. The implantation depth
profiles are calculated by using the Monte Carlo simulator TRIM. The
fabrication process and the I--V and C--V characteristics
of the lateral Ti/4H-SiC Schottky barrier diodes (SBDs) fabricated
on these multiple box-like ion-implantation layers are presented in
detail. Measurements of the reverse I--V characteristics
demonstrate a low reverse current, which is good enough for many
SiC-based devices such as SiC metal--semiconductor field-effect
transistors (MESFETs), and SiC static induction transistors (SITs).
The parameters of the diodes are extracted from the forward I--V
and C--V characteristics. The values of ideality factor n of
SBDs for samples A and B are 3.0 and 3.5 respectively, and the
values of series resistance R_\rm s are 11.9 and 1.0~kΩ
respectively. The values of barrier height φ _\rm B of
Ti/4H-SiC are 0.95 and 0.72 eV obtained by the I--V method and 1.14
and 0.93 eV obtained by the C--V method for samples A and B
respectively. The activation rates for the implanted nitrogen ions
of samples A and B are 2\% and 4\% respectively extracted from
C--V testing results. 相似文献
11.
Two-dimensional growth of GaN thin films on an atomically flat C-face 6H-SiC(0001) surface prepared by ultra-high vacuum Si-etching is observed when using an AlN buffer layer in N plasma-assisted molecular beam epitaxy. Scanning tunneling microscopy and reflection high energy electron diffraction observations reveal a series of Ga-stabilized reconstructions which are consistent with those reported for an N-polar GaN(0001) film. The result, including the effect observed previously for GaN thin film on Si-terminated 6H-SiC(0001), agrees with the polarity assignment of heteroepitaxial wurtzite GaN films on polar 6H-SiC substrates, i.e., GaN film grown on SiC(0001) is <0001> oriented (N-face) while that on SiC(0001) is <0001> oriented (Ga-face). 相似文献
12.
Modeling of the drain-induced barrier lowering effect and optimization for a dual-channel 4H silicon carbide metal semiconductor field effect transistor
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A new analytical model to describe the drain-induced barrier lowering (DIBL) effect has been obtained by solving the two-dimensional (2D) Poisson's equation for the dual-channel 4H-SiC MESFET (DCFET). Using this analytical model, we calculate the threshold voltage shift and the sub-threshold slope factor of the DCFET, which characterize the DIBL effect. The results show that they are significantly dependent on the drain bias, gate length as well as the thickness and doping concentration of the two channel layers. Based on this analytical model, the structure parameters of the DCFET have been optimized in order to suppress the DIBL effect and improve the performance. 相似文献
13.
Modeling of the drain-induced barrier lowering effect and optimization for a dual-channel 4H silicon carbide metal semiconductor field effect transistor
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A new analytical model to describe the drain-induced barrier lowering(DIBL) effect has been obtained by solving the two-dimensional(2D) Poisson’s equation for the dual-channel 4H-SiC MESFET(DCFET).Using this analytical model,we calculate the threshold voltage shift and the sub-threshold slope factor of the DCFET,which characterize the DIBL effect.The results show that they are significantly dependent on the drain bias,gate length as well as the thickness and doping concentration of the two channel layers.Based on this analytical model,the structure parameters of the DCFET have been optimized in order to suppress the DIBL effect and improve the performance. 相似文献
14.
15.
I. A. Bocharova 《Journal of Applied Spectroscopy》2006,73(3):394-399
Using a model relating the change in drain current with modulation of the effective channel thickness upon IR illumination
of GaAs field effect transistors with a Schottky gate (MESFETs), it is shown that it is possible to determine the change in
channel thickness and the concentration profile for deep centers in an FET channel. Profiles are given for the distribution
of deep centers in the channels of GaAs MESFETs with different noise temperatures.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 349–353, May–June, 2006. 相似文献
16.
Low frequency effects of surface states on 4H—SiC metal—semiconductor field effect transistor
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The process-related surface state effect is investigated the fabrication of SiC devices, and a nonllnear model for 4H-SiC power metal-semiconductor field effect transistor (MESFET) is propose, which takes into account the surface related parameters. The frequency-and temperature-dependent transconductance dispersion is readily demonstrated in terms of the improved model. Simulation results show that larger dispersion and higher transition frequency occur in 4H-SiC MESFET than in GaAs MESFET. The advantage of this analytical model over the two-dimensional numerical simulation is the simplicity of calculations, therefore it is suitable for the processing improvement of SiC devices 相似文献
17.
对制备的Ni/4H-SiC肖特基势垒二极管(SBD)进行了γ射线辐照试验,并在辐照过程中对器件分别加0和-30?V偏压.经过1?Mrad(Si)总剂量的γ射线辐照后,不同辐照偏压下的Ni/4H-SiC肖特基接触的势垒高度和理想因子没有退化,SiC外延层中的少子寿命也没有退化.辐照后器件的反向电流下降,这是由于器件表面的负界面电荷增加引起的.研究表明,辐照偏压对Ni/4H-SiC SBD的辐照退化效应没有明显的影响.
关键词:
碳化硅
肖特基
辐照效应
偏压 相似文献
18.
19.
本文提出了一种带栅漏间表面p型外延层的新型MESFET结构并整合了能精确描述4H-SiC MESFET工作机理的数值模型,模型综合考虑了高场载流子饱和、雪崩碰撞离化以及电场调制等效应. 利用所建模型分析了表面外延层对器件沟道表面电场分布的改善作用,并采用突变结近似法对p型外延层参数与器件输出电流(Ids)和击穿电压(VB)的关系进行了研究.结果表明,通过在常规MESFET漏端处引入新的电场峰来降低栅极边缘的强电场峰并在栅漏之间的沟道表面引入p-n结内建电场进一步降低电场峰值,改善了表面电场沿电流方向的分布.通过与常规结构以及场板结构SiC MESFET的特性对比表明,本文提出的结构可以明显改善SiC MESFET的功率特性.此外,针对文中给定的器件结构,获得了优化的设计方案,选择p型外延层厚度为0.12 μupm,掺杂浓度为5× 1015 cm-3,可使器件的VB提高33%而保持Ids基本不变. 相似文献
20.
High energy electron radiation effect on Ni and Ti/4H-SiCSchottky barrier diode at room temperature
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This paper reports that Ni and Ti/4H-SiC Schottky barrier diodes
(SBDs) were fabricated and irradiated with 1~MeV electrons up to a
dose of 3.43×1014~e/cm2. After radiation, the Schottky
barrier height φ B of the Ni/4H-SiC SBD increased from
1.20~eV to 1.21~eV, but decreased from 0.95~eV to 0.94~eV for the
Ti/4H-SiC SBD. The degradation of φ B could be
explained by interface states of changed Schottky contacts. The
on-state resistance RS of both diodes increased with the
dose, which can be ascribed to the radiation defects. The reverse
current of the Ni/4H-SiC SBD slightly increased, but for the Ti/4H-SiC
SBD it basically remained the same. At room temperature,
φ B of the diodes recovered completely after one week,
and the RS partly recovered. 相似文献