退火对Al/CdZnTe肖特基接触特性的影响

在CdZnTe表面采用真空蒸镀制备了Au和Al电极,研究了在N_2氛围退火对Al/CdZnTe接触特性的影响。退火温度在100℃到300℃之间变化,退火时间为5 min。采用Agilent4155c半导体测试仪测试了样品在不同温度退火后的I-V特性。采用Agilent 4294A高精度阻抗分析仪测试了样品在不同温度退火后的C-V特性。I-V和C-V曲线表明,低温退火会使接触势垒高度增加,理想因子趋近于1,电容值下降为退火前的一半左右。当退火温度高于250℃时,接触势垒高度下降,理想因子偏离1,电容值下降近一个数量级。     

金属/半导体肖特基接触模型研究进展

在分析理想金属/半导体肖特基接触的基础上,概述了一般情形下肖特基接触的形成机理和影响因素。金属/半导体间的界面层使得肖特基势垒高度(SBH)对功函数的依赖减弱,也导致SBH与外加偏压有关。研究证实,多种因素,如界面晶向、原子结构、化学键和结构不完整性等,都会造成SBH的空间不均匀分布。该特性在肖特基接触中普遍存在,并对基于肖特基结的器件工作有显著影响。     

金属/多晶锗硅肖特基接触特性的影响因素研究

用射频磁控溅射在单晶硅上沉积Si1-xGex薄膜.溅射的SiGe薄膜样品,用俄歇电子谱(AES)测定其Ge含量,约为17％,即Si0.83Ge0.17.样品分别做高温磷、硼扩散,经XRD测试为多晶态,制得n,p-poly-Si0.83Gge0.17.在n-poly-Si0.83Ge0.17上分别溅射Ni、V、W、Cu、Pt、Ti、Al、Co膜,做成金属/n-poly-Si0.83Ge0.17肖特基结.利用Ⅰ-Ⅴ测试数据进行接触参数的提取,从而定量研究金属的功函数、金属膜厚以及快热退火温度对肖特基接触特性的影响.结果发现,肖特基势垒高度(SBH)与金属的功函数有微弱的正相关,Al/n,p-poly-Si0.83Ge0.17接触存在Shannon效应,金属膜厚对Co/n,p-poly-Si0.83Ge0.17接触特性有不同的影响,随快热退火温度的升高,Ni、V、W、Co、Cu、Pt、Ti、Al八种金属在n-poly-Si0.83Ge0.17上的肖特基势垒高度和理想因子未见有一致的变化规律,但存在不均匀性.     

GaN肖特基紫外探测器分析

随着科学技术的不断进步,GaN基紫外材料在社会生产已经得到了广泛地应用,这项技术的充分发展,被认为是和发光二极管、激光器具有同样作用的一种器材。基于宽禁带半导体材料的GaN紫外探测器由于具有探测波长可调控性、工艺兼容性好、构造种类比较繁多等特点,现阶段它已经成为了同行界广泛研究的一个对象。GaN肖特基结构紫外探测器因为其具有很好的相应性能与很快的反应速度所以受到业界人士的如此青睐。笔者以肖特基结构探测器的不足之处作为着手点,研究并分析了这种新型的GaN肖特基结构紫外探测器。     

rGO-AuNPs/n-Si的肖特基接触特性研究

通过水热法制备了还原氧化石墨烯负载Au纳米复合材料(rGO-AuNPs),结合旋涂法,将其涂覆在单晶硅表面,制备出rGO-AuNPs/n-Si肖特基接触。结果表明,rGO-AuNPs的衍射峰以单质Au为主,存在较弱的石墨烯衍射峰,同时纳米Au粒子(Au nanoparticles, AuNPs)较均匀分布在石墨烯表面,表明成功合成了负载Au的还原氧化石墨烯。从电流-电压(Current-voltage,I-V)曲线可以看出rGO-AuNPs/n-Si肖特基接触具有整流特性。在负载量下,随着Au含量的递增,肖特基势垒高度增加,理想因子减小,但漏电流增大,可能是由于氧化石墨烯在还原过程中缺陷的存在,产生了隧道电流和镜像力,降低了肖特基势垒的横向均匀性。     

ZnO上肖特基接触的研究进展

由于ZnO存在本征施主缺陷(锌间隙和氧空位),使得表面存在较高浓度的施主能级,难以获得肖特基接触.本文回顾了近年来在n型ZnO上制备肖特基接触的研究进展,对n型ZnO上制备肖特基接触的Au、Pt、Pd、Ag等金属方案的性能与特点,以及影响接触性能等因素,如表面处理和退火等进行了分析与归纳.同时,对P型ZnO上难以获得肖特基接触的原因进行了讨论.另外,由于Au、Pt等金属普遍存在热稳定差的问题,会降低ZnO基大功率器件的寿命,寻找能与n型ZnO能形成高热稳定性、低泄露电流、高势垒高度的肖特基接触材料是未来ZnO上肖特基光电器件的发展方向.     

外加偏压对未退火Co/n-poly-SiGe肖特基接触特性的影响

采用直流离子束溅射法,在n型单晶硅衬底上淀积Si1-xGex薄膜.俄歇电子谱(AES)测得Si1-xGex薄膜的Ge含量约为0.15.对薄膜进行高温磷扩散后,经XRD测试为多晶态,即得n-poly-Si0.85Ge0.15.在n-poly-Si0.85Ge0.15上溅射一层薄的Co膜,做成Co/n-poly-Si085Ge0.15肖特基结样品.在90～332 K范围对未退火样品做I-V-T测试.研究发现,随着外加偏压增大,表观理想因子缓慢上升,肖特基势垒高度(SBH)下降.基于SBH的不均匀分布建模,得到了二者近似为线性负相关的结论.     

金属与半导体肖特基接触势垒模型及其载流子传输机制的研究进展

肖特基结具有整流特性,在整流器和光电检测等电子元器件制造中有极其重要的应用,重点介绍了相关研究人员在金属与半导体肖特基接触势垒的形成机理、相关数学模型及其影响因素等方面的研究进展。有研究表明,肖特基势垒的形成主要是由于费米能级的钉扎,而费米能级钉扎则源于界面新相的形成或界面极化键的存在。同时,在肖特基势垒的相关模型中,热电子激发模型是目前应用最为广泛的、用于解释界面载流子传输机制的肖特基接触势垒模型。随着对接触界面载流子传输机制的深入研究,热发射-扩散、热场发射等载流子传输机制模型相继被研究者提出。另外,相关研究表明,快速退火处理可导致肖特基接触界面处的原子扩散、重排、新相生成等现象,对肖特基接触的稳定性产生重要影响。     

ZnO上欧姆接触的研究进展

为制备高性能的ZnO基器件如UV光发射器，探测器、场效应晶体管，在ZnO上形成优良的金属电极是十分必要的。回顾了近年来ZnO上制备欧姆接触的新进展，对在n型ZnO上制备欧姆接触的Al，A1/Pt，A1/Au，Ti/Al，Ti，AU，Ti/A1/Pt/Au，Re/Ti/Au等金属化方案的性能与特点，以及影响欧姆接触电阻率和热稳定性的因素，如表面处理和退火等进行了分析与归纳。同时，对P型ZnO上难以获得低接触电阻的原因进行了讨论。文章还简要说明了ZnO上透明欧姆接触的研究现状，指出获得低阻、高导电、高透光和高热稳定性的接触是未来ZnO基光电器件的发展方向。     

低温等离子体处理对纤维表面的影响

本文介绍了用低温等离子体处理纤维的情况，用低温等离子体处理羊毛纤维引起了 羊毛表面成份和表面结构的某些变化，但不会使基体性质改变。因此增加了处理后的羊 毛纤维的可湿性。改善了染色性能。结果表明，等离子体处理将成为印染工艺的一个新 方法。     

肖特基型氮铝镓紫外光电探测器

通过采用插入缓冲层的办法,利用金属有机气相外延(MOCVD)得到高质量的AlGaN薄膜,克服了AlGaN薄膜容易产生裂纹的缺点.在此基础上,我们通过采用传统的紫外光刻和湿法刻蚀的方法,制备得到了金属-半导体-金属(MSM)结构的Al0.25Ga0.75N紫外光电探测器.结果表明,在1 V偏压下,器件的暗电流仅为20 pA,如此低的暗电流主要是由于器件中存在一定量的缺陷而导致电阻过大的原因造成的.器件的最高峰值出现在308 nm,大小为0.07 A/W,器件的上升时间为10 ns,下降时间为190 ns.     

Schottky contact of zinc onp-germanium

Metal-semiconductor contacts are drawing increasing attention due to their potential for applications in devices and integrated circuits. Experimentally, lower barrier heights have been reported more often for metallic contacts onp-type semiconductors. Here we report our results regarding barrier height of zinc onp-type germanium. The result is discussed in light of the mechanisms which could reduce the pinning effect in such contacts which are normally thought to be responsible for the observation of low barrier heights onp-type semiconductors.     

Schottky contacts of refractory metal nitrides on gallium nitride using reactive sputtering

Schottky contacts of refractory metal nitrides formed by reactive sputtering on n-type gallium nitride (GaN) were electrically evaluated, including film resistivity, Schottky characteristics and thermal stability. For the metal nitrides of TiN_x, MoN_x and ZrN_x, resistivities of 108.3, 159.0 and 270.0 μΩcm were obtained, respectively. Current-voltage (I-V) characteristics showed that the ideality factor varied from 1.03 to 1.16, while the Schottky barrier height (SBH) varied from 0.66 to 0.79 eV for the three kinds of Schottky contacts. Especially for the ZrN_x contact, the ideality factor and SBH were improved after annealing at 800 °C for 30 s. Schottky contact utilizing a refractory metal nitride on GaN shows its potential to develop thermally stable GaN devices.     

The effect of high temperature annealing on Schottky diode characteristics of Au/n-Si contacts

The current-voltage and capacitance-voltage characteristics of Au/n-Si/Al Schottky barrier diode were measured in the temperature range of 100-800 °C. Au/n-Si/Al Schottky barrier diode annealed at temperatures from 100 °C to 400 °C for 5 min and from 500 °C to 800 °C for 7 min in N₂ atmosphere. The electronic parameters such as barrier height and ideality factor (n) of the device were determined using Cheung's method. To determine whether or not a Schottky diode is ideal it can be used the ideality factor (n) found from its forward current-voltage (I-V) characteristics. It has been found that the value of Φ_b (0.82 or 0.83 eV) remains constant up to 500 °C and 0.80 and 0.79 eV in 600, 750 °C respectively in the forward I-V mode. An ideality factor value of 1.04 was obtained for as-deposited sample. The ideality factor n varied from 1.04 to 2.30. The experimental results have shown that the ideality factor (n) values increases with increasing annealing temperature up to 750 °C. This has been explained in terms of the presence of different metallic-like phases produced by chemical reactions between the Au and Si substrate because of the annealing process. The Φ_b (C-V) values obtained from the reverse-bias C⁻²-V curves of the as-deposited and annealed diode are in the range 0.99-1.12 eV. The difference between Φ_b (C-V) and the Φ_b (I-V) is in close agreement with values reported in literature. Besides Fermi energy level and carrier concentration determined by using thermionic emission (TE) mechanism show strong temperature dependence. It has been seen current-voltage characteristics of the diode show an ideal behavior.     

AlGaN/GaN肖特基二极管中金属电极的制备方法研究

本文主要研究AlGaN/GaN二极管制备工艺中Ohmic Contact金属和Schottky Contact金属电极的制备,主要讨论了金属电极材料的选取,退火温度和退火时间对接触电阻的影响,最后得出了Ohmic Contact的比接触电阻和TiN的淀积参数。     

Influence of rapid thermal annealing effect on electrical and structural properties of Pd/Ru Schottky contacts to n-type GaN

Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I–V) and 0.79 eV (C–V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I–V) and 0.96 eV (C–V) for the contact annealed at 300 °C. However, both I–V and C–V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 °C and 500 °C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 °C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I–V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 °C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 °C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high-temperature device applications.     

Nitride-based Schottky diodes and HFETs fabricated by photo-enhanced chemical wet etching

Photo-enhanced chemical (PEC) wet etching technology was used to etch GaN and AlGaN epitaxial layers. It was found that the maximum etch rates were 510, 1960, 300, and 0 nm/mm for GaN, Al_0.175Ga_0.825N, Al_0.23Ga_0.77N, and Al_0.4Ga_0.6N, respectively. It was also found that we could achieve a high Al_0.175Ga_0.825N to GaN etch rate ratio of 12.6. Nitride-based Schottky diodes and heterostructure field effect transistors (HFETs) were also fabricated by PEC wet etching. It was found that we could achieve a saturated I_D larger than 850 mA/mm and a maximum g_m about 163 mS/mm from PEC wet etched HFET with a 0.5 μm gate length. Compared with dry etched devices, the leakage currents observed from the PEC wet etched devices were also found to be smaller.     

Impact of SF6 plasma treatment on performance of AlGaN/GaN HEMT

Selective plasma treatment of an AlGaN/GaN heterostructure in the RF discharge of the electronegative SF₆ gas was studied. Shallow recess-gate etching of AlGaN (∼5 nm) was performed in CCl₄ plasma through a photoresist mask. Subsequently, recess-gate etching followed in situ by SF₆ plasma. The plasma treatment provides the following advantages in the technology of AlGaN/GaN high-electron mobility transistors (HEMT): It (1) simplifies their technology; (2) ensures sufficient selectivity; and (3) enables the technologist to set the threshold voltage of the HEMTs controllably. At the same time, the treatment can (1) provide the AlGaN/GaN heterostructure with surface passivation; (2) modify the 2DEG in any area of a HEMT channel; and (3) make it possible to convert a HEMT operation from depletion mode to enhancement mode. The treatment also improved significantly the DC and RF parameters of HEMTs studied.     

Photovoltaic and interface state density properties of the Au/n-GaAs Schottky barrier solar cell

The electrical and photovoltaic properties of the Au/n-GaAs Schottky barrier diode have been investigated. From the current-voltage characteristics, the electrical parameters such as, ideality factor and barrier height of the Au/n-GaAs diode were obtained to be 1.95 and 0.86 eV, respectively. The interface state distribution profile of the diode as a function of the bias voltage was extracted from the capacitance-voltage measurements. The interface state density D_it of the diode was found to vary from 3.0 × 10¹¹ eV⁻¹ cm⁻² at 0 V to 4.26 × 10¹⁰ eV⁻¹cm⁻² at 0.5 V. The diode shows a non-ideal current-voltage behavior with the ideality factor higher than unity due to the interfacial insulator layer and interface states. The diode under light illumination exhibits a good photovoltaic behavior. This behavior was explained in terms of minority carrier injection phenomenon. The photovoltaic parameters, such as open circuit voltage and short circuit current density were obtained to be 362 mV and J_sc = 28.3 μA/cm² under AM1, respectively.