Ti/4H-SiC肖特基势垒二极管抗辐射特性的研究

本文采用γ射线、高能电子和中子对Ti/4H-SiC肖特基势垒二极管(SBD)的抗辐射特性进行了研究.研究发现对于γ射线和1 MeV电子辐照,-30 V辐照偏压对器件的辐照效应没有明显的影响.经过1 Mrad(Si)的γ射线或者1×l0¹³ n/cm²的中子辐照后,Ti/4H-SiC肖特基接触都没有明显退化;经过3.43×10¹⁴ e/cm²的1 MeV电子辐照后Ti/4H-SiC的势垒高度比辐照前轻微下降,这是由于高能 关键词： 碳化硅 肖特基 辐照 偏压     

60Coγ射线辐照对肖特基二极管1/f噪声的影响

在肖特基二极管(schottky barrier diode,SBD)辐照损伤机理和总剂量效应分析的基础上,利用1/f噪声的迁移率涨落和载流子数涨落模型,深入研究辐照损伤对器件1/f噪声的影响.研究结果表明,辐照诱生新的界面态,改变界面态密度分布,进而调制了肖特基势垒高度,增大表面复合速度是引起器件性能退化主要原因,也是1/f噪声剧烈增加的主要原因.正因为如此,噪声与器件退化存在相关性,即噪声拟合参数B越大,偏离标准值越多,器件可靠性越差,抗辐照能力越低,在辐照环境下工作越容易失效.由此可知,1/f噪声特性可以用作SBD辐照损伤机理的研究工具,并有可能用于SBD抗辐射加固的无损评估.     

60Co γ-射线辐照对肖特基二极管1/f噪声的影响

在肖特基二极管(Schottky barrier diode,SBD)辐照损伤机理和总剂量效应分析的基础上,利用1/f噪声的迁移率涨落和载流子数涨落模型,深入研究辐照损伤对器件1/f噪声的影响. 研究结果表明,辐照诱生新的界面态,改变界面态密度分布,进而调制了肖特基势垒高度,增大表面复合速度是引起器件性能退化主要原因,也是1/f噪声剧烈增加的主要原因. 正因为如此,噪声与器件退化存在相关性,即噪声拟合参数B越大,偏离标准值越多,器件可靠性越差,抗辐照 关键词： 肖特基二极管 f噪声')" href="#">1/f噪声 60Co γ射线')" href="#">⁶⁰Co γ射线 界面态     

4H-SiC探测器的γ辐照影响研究

为研究4H-SiC探测器的抗γ辐照性能,使用40万Ci级的60Co源对4H-SiC探测器进行了数次辐照,累积辐照剂量最大为1 MGy(Si),并在辐照后对4H-SiC的性能进行了测试。随着累积辐照剂量增加,4H-SiC探测器的正向电流增大,而反向电流恰好相反;根据4H-SiC探测器的正向I-V曲线可提取理想因子和肖特基势垒,理想因子从1.87增加到2.18,肖特基势垒从1.93 V减小至1.69 V;4H-SiC探测器对241Am源产生的α粒子进行探测时,探测器的电荷收集率从95.65%退化到93.55%,测得能谱的能量分辨率由1.81%退化到2.32%。4H-SiC探测器在受到1 MGy(Si)的γ辐照后,与未受到辐照时相比,在探测能量为5.486 MeV的α粒子时能量分辨率和电荷收集率仅退化了28.18%和2.2%,仍具备优良的探测性能。     

绝缘体上硅金属氧化物半导体场效应晶体管中辐射导致的寄生效应研究

基于⁶⁰Co γ射线源研究了总剂量辐射对绝缘体上硅（silicon on insulator,SOI）金属氧化物半导体场效应晶体管器件的影响.通过对比不同尺寸器件的辐射响应,分析了导致辐照后器件性能退化的不同机制.实验表明：器件的性能退化来源于辐射增强的寄生效应;浅沟槽隔离（shallow trench isolation,STI）寄生晶体管的开启导致了关态漏电流随总剂量呈指数增加,直到达到饱和;STI氧化层的陷阱电荷共享导致了窄沟道器件的阈值电压漂移,而短沟道器件的阈值电压漂移则来自于背栅阈值耦合;在同一工艺下,尺寸较小的器件对总剂量效应更敏感.探讨了背栅和体区加负偏压对总剂量效应的影响,SOI器件背栅或体区的负偏压可以在一定程度上抑制辐射增强的寄生效应,从而改善辐照后器件的电学特性.     

不同栅压下Si-n型金属氧化物半导体场效应管总剂量效应的瞬态特性仿真

为了实现半导体器件在电离辐射环境中电学特性的动态退化过程,本文基于总剂量效应中陷阱对载流子的俘获/发射过程,建立了Si-n型金属氧化物半导体场效应管总剂量效应的瞬态特性数值模型.仿真了不同栅极偏压下,器件电学特性随累积总剂量的上升而造成的器件退化效应,并提取了Si/SiO₂界面和栅氧化层中陷阱电荷的变化.仿真发现,随着累计总剂量的上升,两个位置处陷阱电荷的数量都趋向于饱和.当辐照中栅极偏压为正时,器件阈值电压的退化幅度显著高于辐照偏压为负时的退化幅度.无论是辐照过程中栅极加正偏压还是反偏压,都表现出阈值电压的退化幅度随着偏压幅值上升先上升再下降的趋势.栅极偏压对器件辐照后的退火效应也有一定的影响,在退火过程中如果栅极偏压不为零,器件退火后的电学特性恢复幅度比零偏压下的要低一些.     

金属-氧化物-半导体器件γ辐照温度效应

研究了金属-氧化物-半导体(MOS)器件在γ射线辐照条件下的温度效应.采用加固的CC4007进 行辐照实验,在不同温度、不同偏压,以及不同退火条件下对MOS器件的辐照效应进行了比 较,发现温度对辐照效应的影响主要是决定界面态建立的快慢.高温下辐照的器件,界面态 建立的时间缩短.根据实验结果对器件阈值电压漂移的机理进行了探讨. 关键词： 金属-氧化物-半导体场效应 辐射效应 阈值电压漂移     

High energy electron radiation effect on Ni and Ti/4H-SiCSchottky barrier diode at room temperature

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 R_S 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 R_S partly recovered.     

基于4H-SiC肖特基势垒二极管的γ射线探测器

针对极端环境下耐高温和耐辐照半导体核探测器的研制需求,采用外延层厚度为100μm的4H碳化硅(4H-SiC)制备成肖特基二极管探测器,研究了该探测器对~(241)Am源γ射线的能谱响应.采用磁控溅射金属Ni制备了肖特基二极管的欧姆接触和肖特基接触,利用室温电流-电压和电容-电压测试研究了二极管的电学特性.欧姆特性测试表明,1050°C退火时,欧姆接触特性最好.从正向电流-电压曲线得出二极管肖特基势垒高度为1.617 eV,理想因子为1.127,表明探测器具备良好的热电子发射特性.从电容-电压曲线获得二极管外延层净掺杂浓度为2.903×10~(14)cm~(-3),并研究了自由载流子浓度在外延层中的纵向分布.在反向偏压为500 V时,二极管的漏电流只有2.11 nA,具有较高的击穿电压.测得在-300 V条件下,SiC二极管探测器对能量为59.5 keV的γ射线的能量分辨率为9.49%(5.65 keV).     

GaN基多量子阱蓝光LED的γ辐照效应

本文用4×104Ci(1Ci=3.7×1010Bq)的60Co源(剂量率2×105rad(Si)/h)对GaN基InGaN/GaN多量子阱蓝光LED进行5种剂量的γ射线的辐照实验.通过辐照前后蓝光LED的波长、色纯度、最大半峰宽(FWHM)和电流-电压(I-V)、电流-光通量(I-F)等电光学特性分析,得到γ射线对GaN基LED器件的辐照效应.结果发现,辐照后LED器件的发光一致性和均匀性变差,在20mA工作电流下,最大剂量下器件发光强度衰减近90%,光通量衰减约40%,并得到器件的抗辐照能力的参数τ0Kγ为4.039×10-7rad.s-1,发现较低的正向偏压下(小于2.6V)器件的饱和电流随辐照总剂量增大而增大.     

High energy electron radiation effect on Ni/4H-SiC SBD and Ohmic contact

The Ni/4H-SiC Schottky barrier diodes (SBDs) and transfer length method (TLM) test patterns of Ni/4H-SiC Ohmic contacts were fabricated, and irradiated with 1~MeV electrons up to a dose of 3.43× 10¹⁴~e/cm^-2. After radiation, the forward currents of the SBDs at 2~V decreased by about 50%, and the reverse currents at -200~V increased by less than 30%. Schottky barrier height (φ _B ) of the Ni/4H-SiC SBD increased from 1.20~eV to 1.21~eV under 0~V irradiation bias, and decreased from 1.25~eV to 1.19~eV under -30~V irradiation bias. The degradation of φ _B could be explained by the variation of interface states of Schottky contacts. The on-state resistance (R_s) and the reverse current increased with the dose, which can be ascribed to the radiation defects in bulk material. The specific contact resistance (\rho_c) of the Ni/SiC Ohmic contact increased from 5.11× 10⁵~Ωega.cm² to 2.97× 10^-4~Ωega.cm².     

4H-SiC肖特基二极管的电荷收集特性

针对极端环境下耐辐照半导体核探测器的研制需求,采用耐高温、耐辐照的4H碳化硅(4H-SiC)宽禁带材料制成肖特基二极管,研究了该探测器对241Am源粒子的电荷收集效率。从电容-电压曲线得出该二极管外延层净掺杂数密度为1.991015/cm3。从正向电流-电压曲线获得该二极管肖特基势垒高度为1.66 eV,理想因子为1.07,表明该探测器具备良好的热电子发射特性。在反向偏压高达700 V时,该二极管未击穿,其漏电流仅为21 nA,具有较高的击穿电压。在反向偏压为0~350 V范围内研究了该探测器对3.5 MeV 粒子电荷收集效率,在0 V时为48.7%,在150 V时为99.4%,表明该探测器具有良好的电荷收集特性。     

The barrier-height inhomogeneity in identically prepared Ni/n-type 6H-SiC Schottky diodes

The effective barrier heights and ideality factors of identically fabricated Ni/n-type 6 H-SiC Schottky diodes (23 dots) have been calculated from their experimental forward bias current–voltage (I–V) and reverse bias capacitance–voltage (C–V) characteristics. A statistical study related to the experimental barrier heights (BHs) and ideality factors of the diodes has been made. The effective Schottky barrier heights (SBHs) and ideality factors obtained from the I–V and C–V characteristics have differed from diode to diode. The BHs obtained from the I–V characteristics varied from 0.85 to 1.03 eV, the ideality factors varied from 1.13 to 1.40 and the BHs from C^-2–V characteristics varied from 1.10 to 1.70 eV. The experimental BH and ideality factor distributions obtained from the I–V characteristics are fitted by a Gaussian function, and their mean values are found to be 0.92±0.04 eV and 1.29±0.08 eV, respectively. The lateral homogeneous SBH value of 1.16 eV for the Ni/n-type 6H-SiC diodes has been calculated from a linear extrapolation of the effective barrier heights to n_if=1.03. PACS 79.40.+z; 73.40.Sx; 73.30.+y; 71.20.Nr     

Fabrication and characteristics of lateral Ti/4H-SiC Schottky barrier diodes

This paper describes the fabrication and characteristics of the lateral Ti/4H-SiC Schottky barrier diodes (SBDs). SBDs are fabricated by nitrogen ion implantation into p-type 4H-SiC epitaxial layer. The implant depth profile is simulated using the Monte Carlo simulator TRIM. Measurements of the reverse I－V characteristics demonstrate a low reverse current, that is good enough for many SiC-based devices such as SiC metal-semiconductor field-effect transistors, and SiC static induction transistors. The parameters of the diodes are extracted from the forward I－V characteristics. The barrier height φ_b of Ti/4H-SiC is 0.95 eV.     

SiC epitaxial layers grown by chemical vapour deposition and the fabrication of Schottky barrier diodes

This paper presents the results of unintentionally doped 4H-SiC epilayers grown on n-type Si-faced 4H-SiC substrates with 8° off-axis toward the [11\overline 2 0] direction by low pressure horizontal hot-wall chemical vapour deposition. Growth temperature and pressure are 1580~°C and 10⁴~Pa, respectively. Good surface morphology of the sample is observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) are used to characterize epitaxial layer thickness and the structural quality of the films respectively. The carrier concentration in the unintentional 4H-SiC homoepitaxial layer is about 6.4×10¹⁴~cm^-3 obtained by c--V measurements. Schottky barrier diodes (SBDs) are fabricated on the epitaxial wafer in order to verify the quality of the wafer and to obtain information about the correlation between background impurity and electrical properties of the devices. Ni and Ti/4H-SiC Schottky barrier diodes with very good performances were obtained and their ideality factors are 1.10 and 1.05 respectively.     

Fabrications and characterizations of high performance 1.2 kV,3.3 kV,and 5.0 kV class 4H–SiC power SBDs

In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H–SiC power Schottky barrier diodes(SBDs)are fabricated with three N-type drift layer thickness values of 10 μm, 30 μm, and 50 μm, respectively. The avalanche breakdown capabilities,static and transient characteristics of the fabricated devices are measured in detail and compared with the theoretical predictions. It is found that the experimental results match well with the theoretical calculation results and are very close to the 4H–SiC theoretical limit line. The best achieved breakdown voltages(BVs) of the diodes on the 10 μm, 30 μm, and 50 μm epilayers are 1400 V, 3320 V, and 5200 V, respectively. Differential specific-on resistances(R_(on-sp)) are 2.1 m?·cm~2,7.34m?·cm~2, and 30.3 m?·cm~2, respectively.     

Influence of deep defects on electrical properties of Ni/4H-SiC Schottky diode

In this paper, we investigate the influence of deep level defects on the electrical properties of Ni/4H-SiC Schottky diodes by analyzing device current-voltage(I-V) characteristics and deep-level transient spectra(DLTS). Two Schottky barrier heights(SBHs) with different temperature dependences are found in Ni/4 H-SiC Schottky diode above room temperature. DLTS measurements further reveal that two kinds of defects Z_(1/2) and Ti(c)~a are located near the interface between Ni and SiC with the energy levels of E_C-0.67 eV and E_C-0.16 eV respectively. The latter one as the ionized titanium acceptor residing at cubic Si lattice site is thought to be responsible for the low SBH in the localized region of the diode, and therefore inducing the high reverse leakage current of the diode. The experimental results indicate that the Ti(c)~a defect has a strong influence on the electrical and thermal properties of the 4 H-SiC Schottky diode.     

Prediction of lateral barrier height in identically prepared Ni/n-type GaAs Schottky barrier diodes

We have identically prepared Ni/n-GaAs/In Schottky barrier diodes (SBDs) with doping density of 7.3 × 10¹⁵ cm⁻³. The barrier height for the Ni/n-GaAs/In SBDs from the current-voltage characteristics have varied from 0.835 to 0.856 eV, and ideality factor n from 1.02 to 1.08. We have determined a lateral homogeneous barrier height value of 0.862 eV for the Ni/n-GaAs/In SBD from the experimental linear relationship between barrier heights and ideality factors.