InGaN/GaN多量子阱LED的电特性研究

针对InGaN/GaN多量子阱LED,分析了占据能态高于势垒的载流子和低于势垒的载流子参与的电流输运机制,从而推导出对应能态电流输运机制下的电流-电压关系,以及理想因子与温度的变化规律.实验结果证实,在低注入强度下,由材料缺陷引入的深能级辅助隧穿输运机制占主导,电流电压特性符合相应的推导结果,随着注入强度的增大,参与扩散-复合输运机制的载流子逐渐增加,温度对输运机制的影响逐渐增大.     

砷化镓汽相外延层-衬底交界面上高阻区中的深能级

为了弄清在 GaAs 汽相外延层和衬底交界面之间引起高阻层的深中心的能级,确立了三种测量方法:(1)肖特基势垒电容与时间的关系,(2)肖特基势垒反向电流与温度的关系,(3)高阻区的光电导。在不同温度下测得的电容随时间变化,从中可以发现,在深阱处的电子激活能大约为0.89电子伏。当耗尽层夹在高阻区内时,则肖特基势垒的反向电流比起通常的反向电流约大三个数量级。有关反向电流与温度的关系以及高阻区中光电导光谱的测量结果表明,在价带上面存在着三个深能级,其范围大约为0.3～0.6电子伏。在高阻区,观察到了非本征负光电导。     

Nd掺杂对BiFeO3薄膜微结构和电学性能的影响

采用化学溶液方法,在LaNiO3/Si(100)衬底上生长了Nd掺杂的BiFeO3薄膜.XRD分析结果表明,随着Nd掺杂量的增加,薄膜晶格变小,Nd掺杂量为20%时,薄膜出现杂相.介电测试表明,随着Nd掺杂量的增加,介电常数和损耗减小,Nd掺杂量为2%的薄膜表现出很强的介电色散现象并出现介电损耗弛豫峰,其符合类德拜模型特征.随着Nd掺杂量增加,薄膜的漏电流减小,在低电场下,电流输运遵从SCLC模型,在高场下,电流输运遵循Poole-Frenkel模型.分析结果表明Nd掺杂对薄膜微结构和电学性能有显著影响.     

聚合物发光器件中输运特性的模拟分析

对聚合物发光二极管 I- V特性的测量发现 ,被测器件内存在着类似于某些无机器件中的负阻现象和“迟滞回线”状场致漂移的伏安特性 .模拟分析表明 ,一种反向势垒的存在及其击穿 ,应是引起负阻现象的原因 .缺陷态的存在及其电荷填充的变化 ,是导致 I- V特性曲线随偏压扫描方向变化的主要原因 .而低场下的接触性能决定着发光二级管载流子的输运性质 :若为非欧姆接触 ,则 I- V曲线可用 F- N隧穿模型来描述 ;若为欧姆接触 ,则应用陷阱电荷限制电流 (TCL)模型来描述     

聚合物发光器件中输运特性的模拟分析

对聚合物发光二极管I-V特性的测量发现,被测器件内存在着类似于某些无机器件中的负阻现象和"迟滞回线”状场致漂移的伏安特性.模拟分析表明,一种反向势垒的存在及其击穿,应是引起负阻现象的原因.缺陷态的存在及其电荷填充的变化,是导致I-V特性曲线随偏压扫描方向变化的主要原因.而低场下的接触性能决定着发光二级管载流子的输运性质:若为非欧姆接触,则I-V曲线可用F-N隧穿模型来描述;若为欧姆接触,则应用陷阱电荷限制电流(TCL)模型来描述.     

基于SiGe/Si的空穴型共振隧穿二极管

用GS400高真空外延设备制备了空穴型双势垒单势阱共振隧道二极管.常温(293K)直流测试数据为PVCR(峰谷电流比)=1.13,Jp(峰值电流)=1.589kA/cm2,对应的低温(77K)脉冲测试数据为PVCR=1.24,Jp=1.086kA/cm2.两种情况下,较低的PVCR可归结为GexSi1-x/Si异质结构本身的能级特性和热效应.     

基于SiGe/Si的空穴型共振隧穿二极管

用GS400高真空外延设备制备了空穴型双势垒单势阱共振隧道二极管.常温(293K)直流测试数据为PVCR(峰谷电流比)=1.13,Jp(峰值电流)=1.589kA/cm2,对应的低温(77K)脉冲测试数据为PVCR=1.24,Jp=1.086kA/cm2.两种情况下,较低的PVCR可归结为GexSi1-x/Si异质结构本身的能级特性和热效应.     

熔体外延法生长的截止波长12 μm的InAs0.04Sb0.96的电学性质

用Van der Pauw法研究了熔体外延(ME)法生长的截止波长为12 μm的InAs0.04Sb0.96单晶电学性质,测量了其电学性质随温度的变化,结果为300 K时,n＝2.3×1016 cm-3,μ＝6×104 cm2/Vs;200 K时,n＝1×1015 cm-3,μ＝1×105 cm2/Vs.分析了石墨舟和石英舟中生长的外延材料不同的电学特性及其散射机理.结果表明,电离杂质散射控制所有样品在低温时的电子输运过程,而高温时材料的电子迁移率主要由极性光学声子的散射过程决定;C的沾污对石墨舟中生长的InAs0.04Sb0.96单晶在200 K以下的电子迁移率有明显的影响.     

磁性材料、超导材料和器件

TM271 02010082双钙社矿SrZCrWO。的磁性与输运性质研究/王锦辉,朱浩,韩红梅,倪刚,钟伟,郡有为(南京大学)11物理学报一2001,5。(3).一5寸O一543研究了双钙钦矿Si渔CrWO6的磁性和输运性质.SrZCrWO6多晶在Ar气及真空气氛中经固相烧结而形成.X射线衍射分析表明主相为Si沈CrWO。,少量杂相为SrWO;.热磁测量表明样品的居里温度为480K左右.电阻随}副变降低而升高,类似于绝缘体,在外场ST,低温下(2 SK)磁致电阻(MR)可达20%但MR随钻踱升高而趋于零.较大的矫顽力(5.97、1少A/m)以及低场部分MR一H曲线偏离高场下的线性曲线,毖云样品可能…     

衬底温度对氧化锌薄膜场发射性能的影响

利用射频磁控溅射法制备了不同衬底温度的氧化锌(ZnO)薄膜.研究了其场发射特性,分析了场发射特性和衬底温度的变化关系.实验结果表明, 开启电场随着衬底温度的增加呈先增大后减小的趋势,场发射特性的变化是由于衬底温度的改变引起表面形貌的变化所致.衬底温度为300 ℃时沉积的ZnO薄膜样品粗糙度最小,场发射性能最差,其开启场强为1.7 V/μm,场强为3.8 V/μm时电流密度仅为0.001 97 A/cm2;衬底温度为400 ℃时沉积的ZnO薄膜样品表面粗糙度最大,场发射特性也优于其他薄膜;开启场强为0.82 V/μm, 场强为3.8 V/μm时电流密度稳定在0.03 A/cm2.Fowler-Nordheim(F-N)曲线为直线表明, 电子是在外加电场的作用下隧穿表面势垒束缚发射到真空的.     

不同场强分布的1064nm激光减反膜损伤特性

设计了两种具有不同场强分布的1 064nm减反射膜结构,即G/H3L/A和G/M2HL/A。采用离子束辅助沉积技术,在K9基底上制备了薄膜,并对薄膜在强激光下的损伤斑形貌及损伤阈值(LIDT)进行了测量。研究结果表明:薄膜的场强分布不同,其抗强激光的能力也不相同。当两种膜系的电场强度(归一化电场强度平方)在薄膜-空气界面处分别为1.039和0.906时,对不同的激光能量(180,150和120mJ),样品G/H3L/A的表面破损斑尺寸均大于样品G/M2HL/A;两种薄膜的激光损伤阈值分别为12.3J/cm2和14.8J/cm2(激光波长为1 064nm,12ns)。这说明,较小的薄膜-空气界面电场强度,有利于激光损伤能力的提高。因此,对于减反射薄膜,在膜系设计时,采用合理的场强分布,降低薄膜-空气界面的电场强度,可以有效改善薄膜的激光损伤特性。     

Spray deposition and characterization of zirconium-oxide thin films

Zirconium oxide films were prepared by the pyrosol process using zirconium acetylacetonate as source material onto clear fused quartz and (100) silicon at substrate temperatures ranging from 300°C to 575°C. X-ray diffraction (XRD) measurements show that samples prepared at substrate temperatures lower than 425°C are amorphous. Films deposited at higher temperatures and short deposition times show a cubic crystalline structure. However, for long deposition times, the samples show monoclinic crystalline structure. A similar phase transformation is observed on samples deposited at short time if they are annealed at high temperature. The cubic and monoclinic phases of the corresponding samples were confirmed by infrared (IR) and Raman spectroscopy, respectively. The ZrO₂ films with cubic phase show an almost stoichiometric chemical composition and refractive index values of the order of 2.1 with an energy band gap of 5.47 eV. The current-density electric-field characteristics of metal-oxide semiconductor (MOS) structures show a small ledge from 2 MV/cm to 4.5 MV/cm, indicating current injection and charge trapping. For higher electric fields, the current is associated with oxygen ion diffusion through the zirconium oxide film. The dielectric breakdown is observed at 6 MV/cm, which is a value higher than those observed in the monoclinic and tetragonal phases.     

硅基(Pb,La)(Zr,Ti)O_3反铁电厚膜的制备及介电性能

采用溶胶–凝胶工艺制备了具有高度(100)择优取向的(Pb,La)(Zr,Ti)O3反铁电厚膜(厚约2.2μm)。研究了该反铁电厚膜在不同温度下的电场诱导相变效应和不同电场强度下的温度诱导相变效应。结果表明:(Pb,La)(Zr,Ti)O3反铁电厚膜在室温下处于反铁电态;随着温度升高,厚膜的相变开关电场强度逐渐降低,反铁电态越来越不稳定,当温度高于132℃且电场强度为0 kV/cm时,厚膜处于顺电态;随着外加电场强度的增大,厚膜的AFE(反铁电态)-FE(铁电态)相变温度向低温方向漂移,当电场强度大于164 kV/cm时,厚膜在室温下已处于铁电态。     

Electrical conduction mechanism in high-dielectric-constant ZrO2 thin films

The electrical conduction mechanism in zirconium oxide (ZrO₂) thin films as a function of temperature T and electric field E was studied. Al/ZrO₂/p-Si metal–insulator–semiconductor (MIS) capacitors were fabricated. With the Al electrode biased negative, the conduction mechanism in the electrical field of 0.81 MV/cm < E < 1.40 MV/cm and in the temperature range of 375 K < T < 450 K is found to be modified Schottky emission. The intrinsic barrier height between Al and ZrO₂ is 1.06 eV. At higher electrical fields of 1.50 MV/cm < E < 2.25 MV/cm and higher temperatures of 375 K < T < 450 K, the electrical conduction is dominated by modified Poole–Frenkel emission. The extracted trap barrier is 0.83 eV. With the Al electrode biased positive, the conduction mechanism is found to be Schottky emission at the electrical field 0.20 MV/cm < E < 0.60 MV/cm and higher temperature range of 425 K < T< 450 K. The barrier height between Si and ZrO₂ is 1.0 eV. Based on these results, an energy band diagram of the Al/ZrO₂/p-Si system is proposed.     

Time dependent breakdown of ultrathin gate oxide

Time dependent dielectric breakdown (TDDB) of ultrathin gate oxide (<40 Å) was measured for a wide range of oxide fields (3.4<|E_ox|<10.3 MV/cm) at various temperatures (100⩽T⩽342°C). It was found that TDDB of ultrathin oxide follows the E model. It was also found that TDDB t₅₀ starts deviating from the 1/E model for fields below 7.2 MV/cm. Below 4.8 MV/cm, TDDB t₅₀ of intrinsic oxide increased above the value predicted by the E model obtained for fields >4.8 MV/cm. The TDDB activation energy for this type of gate oxide was found to have linear dependence on oxide field. In addition, we found that γ (the field acceleration parameter) decreases with increasing temperature. Furthermore, it was found that testing at high temperatures (up to 342°C) and low electric field values did not introduce new gate oxide failure mechanism. It is also shown that TDDB data obtained at very high temperature (342°C) and low fields can be used to generate TDDB model at lower temperatures and low fields. Our results (an enthalpy of activation of 1.98 eV and dipole moment of 12.3 eÅ) are in complete agreement with previous results by McPherson and Mogul. Additionally, it was found that TDDB is exponentially dependent on the gate voltage     

Low electric field breakdown of thin SiO2 films understatic and dynamic stress

A comprehensive study of Time-Dependent Dielectric Breakdown (TDDB) of 6.5-, 9-, 15-, and 22-nm SiO₂ films under dc and pulsed bias has been conducted over a wide range of electric fields and temperatures. Very high temperatures were used at the wafer level to accelerate breakdown so tests could be conducted at electric fields as low as 4.5 MV/cm. New observations are reported for TDDB that suggest a consistent electric field and temperature dependence for intrinsic breakdown and a changing breakdown mechanism as a function of electric field. The results show that the logarithm of the median-test-time-to failure, log (t₅₀), is described by a linear electric field dependence with a field acceleration parameter that is not dependent on temperature. It has a value of approximately 1 decade/MV/cm for the range of oxide thicknesses studied and shows a slight decreasing trend with decreasing oxide thickness. The thermal activation E_a ranged between 0.7 and 0.95 eV for electric fields below 9.0 MV/cm for all oxide thicknesses. TDDB tests conducted under pulsed bias indicate that increased dielectric lifetime is observed under unipolar and bipolar pulsed stress conditions, but diminishes as the stress electric field and oxide thickness are reduced. This observation provides new evidence that low electric field aging and breakdown is not dominated by charge generation and trapping     

Current mechanism and band alignment of Al(Pt)/HfGdO/Ge capacitors

HfGdO high-k gate dielectric thin films were deposited on Ge substrates by radio-frequency magnetron sputtering. The current transport properties of Al(Pt)/HfGdO/Ge MOS structures were investigated at room temperature. The results show that the leakage currents are mainly induced by Frenkel-Poole emissions at a low electric field. At a high electric field, Fowler Nordheim tunneling dominates the current. The energy barriers were obtained by analyzing the Fowler Nordheim tunneling characteristics, which are 1.62 eV and 2.77 eV for Al/HfGdO and Pt/HfGdO, respectively. The energy band alignments for metal/HfGdO/Ge capacitors are summarized together with the results of current-voltage and the x-ray photoelectron spectroscopy.     

Dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22Te thin films

This paper reports the dark conductivity and photoconductivity of amorphous Hg0.78Cd0.22 Te thin films deposited on an Al2O3 substrate by RF magnetron sputtering.It is determined that dark conduction activation energy is 0.417 eV for the as-grown sample.Thermal quenching is absent for the as-grown sample during the testing temperature zone,but the reverse is true for the polycrystalline sample.Photosensitivity shows the maximum at 240 K for amorphous thin films,while it is higher for the as-grown sample than for polycrystalline thin films in the range from 170 to 300 K.The recombination mechanism is the monomolecular recombination process at room temperature,which is different from the low temperature range.Theμτ-product is low in the range of 10-11-10-9 cm2/V,which indicates that some defect states exist in the amorphous thin films.     

飞秒脉冲激光沉积Si基a轴择优取向的钛酸铋铁电薄膜

在钛酸铋(Bi4Ti3O12)薄膜的制备过程中容易获得晶粒c轴垂直于基片表面的薄膜,而压电和铁电存储器主要利用a轴的自发极化分量,因而制备a轴择优取向的Bi4Ti3O12铁电薄膜具有特别的意义。采用飞秒脉冲激光作用在钛酸铋陶瓷靶上,采用Si(111)作为衬底,制备了a轴择优取向的钛酸铋薄膜。采用X射线衍射(XRD)的薄膜附件和场发射扫描电镜(FSEM)研究了薄膜的结构和形貌;采用傅里叶红外光谱仪测量了室温(20℃)下在石英基片上沉积的样品的光学特性;室温下沉积的钛酸铋薄膜呈c轴择优取向,晶粒的平均大小为20 nm,其光学禁带宽度约为1.0 eV。在500℃沉积的钛酸铋薄膜呈a轴择优取向,晶粒大小在30~300 nm之间,薄膜的剩余极化强度Pr为15μC/cm2,矫顽力Er为48 kV/cm。     

Bi_(3.5)Yb_(0.5)Ti_3O_(12)铁电薄膜的制备及性能

采用溶胶-凝胶(Sol-Gel)法在Pt(111)/Ti/SiO2/Si(100)基片上淀积了Bi3.5Yb0.5Ti3O12(BYT)铁电薄膜,研究了在不同退火温度下形成的BYT薄膜的微观结构以及铁电性能方面的区别。结果发现,在610,660,710和760℃不同温度下退火的BYT薄膜的结晶度不同,退火温度越高的BYT薄膜,其结晶度越高。并且发现,BYT薄膜的剩余极化值(2Pr)在710℃以下随退火温度增高而增大,在710℃达到最大;在外加400kV/cm电场时2Pr为36.7μC/cm2,然后随退火温度上升又有所下降。