Si基MOCVD生长AlN深陷阱中心研究

通过PL谱和Raman谱对MOCVD生长Si基AlN的深陷阱中心进行了研究,发现三个深能级Et1,Et2,Et3,分别在Ev上2.61,3.10,2.11eV.Et1是由氧杂质和氮空位(或Al间隙原子)能级峰位靠近重合共同引起的,Et2、Et3都是由于衬底Si原子扩散到AlN引起的.在Si浓度较低时,Si主要以取代Al原子的方式存在,产生深陷阱中心Et2.Si浓度高于某个临界浓度时,部分Si原子以取代N原子位置的方式存在,形成深陷阱中心Et3.实验还表明,即使经高温长时间退火,AlN中Et1和Et2两个深陷阱中心也是稳定的.     

固体C70/Si异质结的界面电子态

用深能级瞬态谱和高频电容-电压技术研究了固体C70/Si异质结的界面电子态.研究结果表明在C70/Si的界面上明显存在三个电子陷阱Eit1(0.194)、Eit2(0.262),Eit3(0.407)和一个空穴陷阱Hit1(0.471),以及在C70/Si界面附近存在着固体C70的电子和空穴陷阱引起的慢界面态.结果还表明C70膜的生长温度对C70/Si的电学性质有重大影响,200℃生长的C70/Si界面远优于室温生长的.     

固体C_(70)/Si异质结的界面电子态

用深能级瞬态谱和高频电容 -电压技术研究了固体 C70 /Si异质结的界面电子态 .研究结果表明在 C70 /Si的界面上明显存在三个电子陷阱 Eit1( 0 .1 94)、Eit2 ( 0 .2 62 ) ,Eit3( 0 .40 7)和一个空穴陷阱 Hit1( 0 .471 ) ,以及在 C70 /Si界面附近存在着固体 C70 的电子和空穴陷阱引起的慢界面态 .结果还表明 C70 膜的生长温度对 C70 /Si的电学性质有重大影响 ,2 0 0℃生长的 C70 /Si界面远优于室温生长的     

GaN基光发射二极管中深能级研究

利用深能级瞬态谱 (DLTS)仪对 Si C衬底上 Ga N基光发射二极管 (LED)中 n-In0 .2 5Ga0 .75N层的深能级进行了研究。在 77K到 3 0 0 K的温度扫描范围内只测量到一个 DLTS峰。该 DLTS峰在反向偏压为 3 V时有一极大值 ,说明 n-In0 .2 5Ga0 .75N层此时全部被耗尽。改变测量的率窗 ,得到该深能级在导带下 0 .2 4e V处 ,浓度为 2 .2 % ND,俘获截面为 1 .93× 1 0 - 1 5cm2。在 Ga N材料中 ,其他小组也报道了此位置上的深能级结果。结合文中的工作 ,该深能级可能和 n-In0 .2 5Ga0 .75N层中的线位错有关。     

Hg1—xCdxTe深缺陷能级研究

利用深能级瞬态谱(DLTS)研究了Hg_(1-x)Cd_xTe(x=0.4)p~+n光伏二极管中的缺陷能级.通过改变注入脉冲条件,获得2个电子陷阱和2个空穴陷阱,电子陷阱的能级位置分别为E(0.06)和E(0.15),空穴陷阱的能级位置分别为H(0.075)和H(0.29).这些深能级的浓度约为浅能级浓度的百分之几.通过改变注入脉冲的宽度,测量了这些能级的多子俘获截面,根据这些深能级的特征参数,估算了器件的少子寿命和零偏压的动态电阻与面积的乘积,并讨论了一些缺陷能级的本质.     

退火对离子注入GaN产生的深能级的影响

我们最近报道了大剂量Al+注入原生GaN后对其光学性质的影响。表明Al+的注入可能产生了某种深能级电子陷阱 ,由于电子陷阱俘获导带电子 ,导致发光猝灭。而经一定条件的退火处理 ,可使深的电子陷阱发生变化 ,因而与缺陷间的跃迁相关的黄色荧光可得到一定程度的恢复。由于注入样品的电阻率高达 1 0 1 2 Ω·cm ,因此不能用已有的常规方法测量。我们为此发展了一种称为“光增强电流谱”(PSCS)新方法 ,用于测量高阻样品中的深能级。研究发现 ,在经过快速退火处理的样品中 ,不能消除由于注入产生的准连续深能级带 ;而在某种常规条件退火的样品中 ,发现了 5个位于导带下 1 .77eV ,1 .2 4eV ,1 .1 6eV ,0 .90eV和 0 .86eV的深电子陷阱 ,它们都是Al+注入经退火后形成的稳定结构。实验发现退火使注入产生的准连续深能级带转变为独立的深能级结构 ,虽不能使GaN的本征发光得到恢复 ,但对黄色荧光的恢复是有利的。此研究有助于了解退火处理对离子注入的GaN的电学结构与发光产生的影响。PSCS的意义在于它适用于测量一切高阻半导体样品中与非辐射跃迁相联系的深陷阱能级 ,而不仅仅适用于测量Al+注入GaN产生的深陷阱能级     

GaAs/Si/AlAs异质结的DLTS实验研究

利用深能级瞬态谱(DLTS)技术研究了Si夹层和GaAs层不同生长温度对GaAs/AlAs异质结晶体品质的影响.发现Si夹层的引入并没有引起明显深能级缺陷,而不同温度下生长的GaAs/Si/AlAs异质结随着温度的降低,深能级缺陷明显增加,并进行了分析,得到深能级是由Ga空位引起的,在600℃时生长的晶体质量最佳.     

低剂量中子辐照氢气氛和氩气氛生长区熔硅的深能级瞬态谱研究

用深能级瞬态谱研究了如下三种N型区熔硅在低剂量中子辐照下的电子陷阱及其退火行为,(1)氩气氛生长,(2)氢气氛生长,(3)氢气氛生长并在中照前作650℃/30分热处理.含氢样品中A中心的生成率约为同剂量中照不含氢样品的50％.由于热释放空位,从室温到190℃热退火过程中A中心和双空位的浓度随退火温度的升高而增加.当退火温度高于230℃,中照含氢硅中A中心和双空位浓度的下降比不含氢硅样品要快得多,这可用原子氢的扩散加速了对缺陷的钝化来解释.等时退火到高于250℃,氢气氛和氩气氛生长区熔硅样品都出现了新的电子陷阱,对它们的可能结构进行了讨论.     

MOCVD生长的硅衬底上GaAlAs/GaAs单量子阱和多量子阱激光器深能级研究

应用深能级瞬态谱(DLTS)技术研究经MOCVD生长的硅衬底上GaAlAs/GaAs 单量子阱和多量子阱激光器深能级.样品的 DLTS谱表明,在激光器的量子阱和 n-GaAlAs 限制层里均存在着一个浓度和俘获截面较大的高温电子陷阱,该陷阱可能与MOCVD生长工艺和质子轰击引进的损伤有关,它直接影响激光器的性能.DX中心和高温电子陷阱在量子阱里可能局域在GaAlAs/GaAs层的界面附近.     

硅中与钼有关能级的研究

利用深能级瞬态谱(DLTS)技术,并通过电子辐照、等时热退火等物理过程,鉴别了Si中与钼有关能级的本质.钼在Si中产生两个主要能级E(0.53)和H(0.36),前者为受主态,后者为施主态,这两个能级都与替位Mo原子有关.     

Interface structure of ultrathin oxide prepared by N/sub 2/O oxidation

With X-ray photoelectron spectroscopy (XPS) measurements, we found in the N/sub 2/O-grown oxide that the nitrogen incorporation should involve the NO or N reaction with the Si-Si bond and P/sub b/ centers at the interface. Consequently, nitrogen content is very low and accumulated mainly at the interface. In addition, we found that the nitrogen atoms at the interface exist in the form of Si-N bonding and the interface oxynitride layer is a mixture of SiO/sub 2/ and Si/sub 3/N/sub 4/ clusters. This structure will result in several undesirable effects. It will give rise to the permittivity and bandgap fluctuations at the interface and hence induced gigantic surface potential fluctuation and mobility degradation in the channel of MOS devices. This bonding structure also explains the interface trap generation during the electrical stressing. The sources of trap generation are attributed to the Si-Si bonds, P/sub b/ centers, and nitride-related defects due to the over-constrained silicon atoms in the Si/sub 3/N/sub 4/ clusters at the interface.     

Al/AlN/Si MIS结构的电学性质

用S i(111)上M OCVD生长的晶态A lN制备出性能良好的A l/A lN/S i(111)M IS结构,用C-V技术首次系统研究了A l/A lN/S iM IS结构的电学性质。用A l/A lN/S iM IS结构的C-V技术测量了A lN的极化特性,得出A lN层的极化强度为-0.000 92 C/m2;揭示了A lN/S i界面存在连续分布的载流子陷阱态,给出了陷阱态密度在S i禁带中随能量的分布;还观察到A lN界面层存在Et-Ev(A lN)=2.55 eV的分立陷阱中心。     

高声速（100）择优取向AIN薄膜的制备和性能研究

采用射频磁控溅射法,通过改变工艺参数在n型（100）Si片上制备了表面粗糙度小、以（100）面择优取向的AlN薄膜。研究了高温退火、N2结尾等工艺对AIN薄膜择优取向的影响。结果表明,增大工作气压有利于薄膜（100）面择优取向,但是随着工作气压升高薄膜沉积不均匀,通过退火可以减少这种缺陷;N2-Ar比低有利于（100）...     

Effect of low-temperature annealing on photoluminescence of silicon nanocluster structures

Experimental data on the photoluminescence spectra of Si nanocluster structures obtained after high-temperature annealing (1150°C) of SiO _x films deposited onto Si and subsequent low-temperature annealing of the films at the temperature 450°C in different ambient are reported. It is shown that the photoluminescence intensity substantially increases after low-temperature annealing and the most-pronounced effect is observed after annealing in the oxygen-nitrogen mixture. In this case, the photoluminescence spectrum is shifted to longer wavelengths and shaped as a broad band with a peak around 800 nm. The processes responsible for the increase in the PL intensity on low-temperature annealing in the oxygen-nitrogen mixture are defined by reconstruction of the Si/SiO₂ interfaces and by energy levels formed at the interfaces and involved in recombination of nonequilibrium charge carriers. The quasichemical reactions that bring about the formation of such levels involve oxygen and nitrogen atoms, and the centers, at which the reactions are initiated, are unsaturated valence bonds at the interfaces between Si nanoclusters and the SiO₂ matrix.     

Characteristics and Electrical Properties of SiNx: H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx:H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition (PECVD). Composition and structure characteristics are detected by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.     

Characteristics and Electrical Properties of SiNx：H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx：H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition （PECVD）. Composition and structure characteristics are detected by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.     

多晶硅后热退火引起SiO_2栅介质可靠性下降的原因分析及其抑制方法

实验研究表明 ,多晶硅后的高温退火明显引起热 Si O2 栅介质击穿电荷降低和 FN应力下电子陷阱产生速率增加 .采用 N2 O氮化则可完全消除这些退化效应 ,而且氮化栅介质性能随着退火时间增加反而提高 .分析认为 ,高温退火促使多晶硅内 H扩散到 Si O2 内同 Si— O应力键反应形成 Si— H是多晶硅后 Si O2 栅介质可靠性退化的主要原因 ;氮化抑制退化效应是由于 N “缝合”了 Si O2 体内的 Si— O应力键缺陷 .     

Wet etching characteristics of a HfSiON high-k dielectric in HF-based solutions

The wet etching properties of a HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing,the etch rate of HfSiON annealed at 900℃ for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interracial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of Si-N bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case.     

掺铒Al_2O_3/Si多层薄膜中纳米晶Si的形成和敏化效应

采用脉冲激光沉积制备了掺铒Al2O3/Si多层薄膜,在淀积过程中脉冲激光溅射产生的高能量Er原子渗透进入非晶硅层,并引入了额外的应力,在低退火温度下诱导形成纳米晶Si。利用纳米晶Si作为敏化剂有效地增强了Er3+在Al2O3中的光致发光。样品微观结构和发光强度的关系表明,获得高密度和小尺寸的纳米晶Si和Er3+处于良好的发光环境是实现优化发光的关键,最优化的Er3+发光强度在退火温度为600℃的条件下得到。     

Effect of Alcohol-Assisted Annealing on the Quality of Silicon Oxide Thin Film

Silicon oxide thin films have been formed by use of the reaction between spin-coated silicone oil and ozone gas at atmospheric pressure and low temperature (250°C). Films formed at this temperature contained Si–OH bonds, owing to inadequate dehydration. To remove the Si–OH bonds at low temperature, the sample was dipped in ethanol at room temperature for 15 min then annealed on a hot plate at 250°C in methanol gas for 30 min. This treatment effectively dissociated the Si–OH bonds. It is believed the Si–OH bonds are replaced by Si-OCH₃ bonds during the alcohol-assisted annealing. The leakage current of the metal-oxide-semiconductor after alcohol-assisted annealing was improved and the hysteresis width was reduced. This indicated that the number of trap sites owing to Si–OH bonds was reduced.