分子束外延生长Si/GaP珐()异质结的界面特性

本文研究了分子束外延(MBE)生长的n-N型Si/GaP(Ⅲ)异质结的界面特性。采用C-V法测量Si/GaP(Ⅲ)异质结的表观载流子浓度分布n(x),从中导出了异质界面的导带失配值和界面电荷密度。实验结果表明,n-N型Si/GaP(Ⅲ)是一种弱整流结构。导带失配△E_c=0.10eV,界面电荷密度σ_i=8.8×10~(10)cm~(-2)。通过表现载流子浓度n(x)的理论计算曲线与实验曲线符合较好,说明了实验结果的可靠性。     

碲镉汞异质结能带结构的优化设计

分别对带隙较宽(较窄)的p型材料在带隙较窄(较宽)的n型材料之上的碲镉汞(MCT)异质结的能带结构进行了理论分析.在应用的理论模型中提出了一个简单的载流子浓度近似模型用于计入载流子简并效应和导带非抛物线性，同时还考虑到了价带失配的影响.就p-n结位置(z_B)和界面电荷密度(Q)两个参数对MCT异质结能带结构的影响进行了系统分析，发现这些影响是不可忽略的.根据这些影响特征，进一步得出了z_B和Q参数之间的优化设计规律. 关键词： 碲镉汞(MCT) 异质结 载流子浓度近似     

用光电子能谱研究 Si/GaP(Ⅲ)异质界面的价带不连续性

介绍在改装的ADES-400型光电子能谱仪上,用Si电子束蒸发的方法生长Si/GaP(Ⅲ)界面的过程,并用光电子能谱原位地分析测量不同条件下生长的Si/GaP(Ⅲ)异质界面的形成状况和价带不连续值△E_v。讨论了△E_v与界面状况和原子能级变化的相互关系,确定了生长有序的突变Si/GaP(Ⅲ)异质界面的条件,得到此时界面的价带不连续值为0.80eV。它与理论计算值基本一致。 关键词：     

Ge/Si异质键合半/绝接触界面态对异质结光电输运特性的影响研究

Ge/Si异质键合技术作为一种新型的通用材料制备工艺,在制备高质量Si基Ge薄膜方面展现出巨大的潜力,是研制高性能Ge/Si光电器件的备选方案之一。现阶段主流的直接键合和等离子体键合方法在制备Ge/Si薄膜时都容易在Ge/Si键合界面处引入纳米氧化锗层(GeO₂),导致Ge/GeO₂及GeO₂/Si半/绝接触界面存在界面态,从而器件性能受影响。基于载流子三大输运方程、非局域隧穿模型及半经典量子解法,构建了低温Ge/Si异质键合界面,研究了键合界面的界面态密度(ISD)对Ge/Si异质结的载流子电学输运、光吸收、复合及高频响应等性能的影响。结果表明,随着ISD的增加,Ge/Si异质结的暗电流增大,同时界面态对载流子的俘获能力加强,导致总电流减小,光谱响应减弱。另外,ISD的增加导致Ge层内的电场减小,高频特性变差。为获得性能良好的键合Ge/Si异质结,ISD必须低于1×10¹² cm^-2。该研究结果为高质量Si基Ge薄膜及高性能Ge/Si光电器件的制备提供了理论指导。     

GS-MBE生长的GaP/Si的XPS研究

利用X射线光电子能谱(XPS)深度剖析方法对气体源分子束外延(GS-MBE)生长的GaP/Si异质结构进行了详细的分析.其结果表明:(1)外延层内Ga、P光电子峰与GaP相相符,且组份分布均匀,为正化学比GaP.(2)在不同富PH₃流量条件下生长的样品,其表面富P量稍有不同,而GaP外延层内的测试结果相同.界面也未见有P的富集.(3)XPS剖析至GaP/Si界面附近,随外延层界面向衬底过渡,Si2p光电子峰向高结合能方向移动,且其结合能高于原衬底p型Si,接近于n型Si.但Ga、P光电子峰未发现有明显能移.(4)在XPS检测限内,外延层内和界面都未见有C、O等沾污.这一研究表明:无污染的本底超高真空、相对过剩的富₃生长环境、成功的Si衬底清洗方法等措施保证了GS-MBE生长出正化学比GaP/Si外延异质结构.     

阻变存储器复合材料界面及电极性质研究

采用基于密度泛函理论的第一性原理对比研究了Cu（111）/HfO₂（001）,Cu（111）/HfO₂（010）,Cu（111）/HfO₂（100）三种复合材料界面模型的失配率、界面束缚能、电荷密度、电子局域函数以及差分电荷密度. 计算结果表明：Cu（111）/HfO₂（010）失配率最小,界面束缚能最大,界面体系相对最稳定;对比电荷密度及电子局域函数图显示,只有HfO₂（010）方向形成的复合材料体系出现了垂直Cu电极方向完整连通的电子通道,表明电子在此方向上具有局域性、连通性,与阻变存储器（RRAM）器件导通方向一致;差分电荷密度图显示,Cu（111）/HfO₂（010）复合材料体系界面处存在电荷密度分布重叠的现象,界面处有电子的相互转移、成键的存在;进一步计算了Cu（111）/HfO₂（010）体系距离界面不同位置的间隙Cu原子形成能,表明越靠近界面Cu原子越容易进入HfO₂ 体内,在外加电压下易发生电化学反应,从而导致Cu导电细丝的形成与断裂. 研究结果可为RRAM存储器的制备及性能的提高提供理论指导和设计工具. 关键词： 阻变存储器 复合材料 界面 电子通道     

AlN-Si(111)异质结构界面陷阱态研究

利用Al_AlN_Si(111) MIS结构电容_频率谱研究了金属有机化学气相沉积法生长的 Si 基AlN的AlN_Si异质结构中的电荷陷阱态. 揭示了AlN_Si异质结构界面电荷陷阱态以及A lN层中的分立陷阱中心. 结果指出：AlN层中存在E_t-E_v=2.55eV的分立陷阱中心；AlN_Si界面陷阱态在Si能隙范围内呈连续分布，带中央态密度最低，N_ss为8×10^11eＶ^-1cm^-2，对应的时间常数τ为8×10^-4s ，俘获截面σn为1.58×10^-14cm^2；在AlN界面层存在三种陷阱 态，导致Al_AlN_Si异质结构积累区电容的频散. 关键词： 界面陷阱态 AlN-Si 电容-频率谱     

电场对GaN/g-C3N4异质结电子结构和光学性质影响的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法研究了GaN/g-C₃N₄异质结的稳定性、电子结构、光学性质及功函数,同时考虑了电场效应.结果表明:GaN/g-C₃N₄范德瓦耳斯异质结的晶格失配率(0.9%)和晶格失配能极低(-1.230 meV/?~2,1?=0.1 nm),说明该异质结稳定性很好,且该异质结在很大程度上保留了GaN和g-C₃N₄的基本电子性质,可作为直接带隙半导体材料.同时,GaN/g-C₃N₄异质结在界面处形成了从GaN指向g-C₃N₄的内建电场,使得光生电子-空穴对可以有效分离,这有利于提高体系的光催化能力.进一步分析可知,外加电场使GaN/g-C₃N₄异质结的禁带宽度有着不同程度的减小,使得电子从价带跃迁至导带更加容易,有利于提高体系的光催化活性;此外,当外加电场高于0.3 V/A以及低于-0.4 ...     

Si/ZnS极性界面能带偏移的同步辐射光电子能谱研究

用同步辐射光电子能谱测量了Si/ZnS（111）及（100）异质结的价带偏移ΔE_v．对于Si/ZnS（111）及（100）两界面，ΔE_v的实验结果均为（1.9±0.1）eV，与已有理论预期值相当符合，但与Maierhofer所报告的ZnS/Si（111）异质结测量结果之间则存在明显差别．该实验结果表明对于Si/ZnS极性界面，互逆性规则（commutativity rule）可能不成立，就此进行了讨论． 关键词：     

(n)nc-Si：H/(p)c-Si异质结中载流子输运性质的研究

采用常规等离子体增强化学气相沉积工艺,以高H₂稀释的SiH₄作为反应气体源和PH₃作为磷原子的掺杂剂,在p型(100)单晶硅((p)c-Si)衬底上, 成功地生长了施主掺杂型纳米硅膜((n)nc-Si:H),进而制备了(n)nc-Si:H/(p)c-Si异质结,并在230—420Ｋ温度范围内实验研究了该异质结的Ｉ-Ｖ特性.结果表明,(n)nc-Si:H/(p)c- Si异质结为一典型的突变异质结构,具有良好的温度稳定性和整流特性.正向偏压下 关键词： (n)nc-Si:H/(p)c-Si异质结 能带模型 电流输运机构 温度特性     

Electronic structure and optical gain of InAsPN/GaP(N) quantum dots

The electronic structure and optical gain of InAsPN/GaP(N) quantum dots (QDs) are investigated in the framework of the effective-mass envelope function theory. The strain distribution is calculated using the valence force field (VFF) method. With GaP barrier, for smaller InAsPN QDs, the minimum transition energy may occur at a lower phosphorous (P) composition, but for larger QDs, the transition energy increases as P composition increases due to the increased bandgap of alloy QDs. When the nitrogen (N) composition increases, the transition energy decreases due to the stronger repulsion between the conduction band (CB) and the N resonant band, and the transition matrix element (TME) is more affected by the transition energy rather than N–CB mixing. To obtain laser materials with a lattice constant comparable to Si, we incorporated 2% of N into the GaP barrier. With this GaP_0.98N_0.02 barrier, the conduction band offset is reduced, so the quantum confinement is lower, resulting in a smaller transition energy and longer wavelength. At the same time, the TME is reduced and the optical gain is less than those without N in the barrier at a low carrier density, but the peak gain increases faster when the carrier density increases. Finally it can surpass and reach a greater saturation optical gain than those without N in the barrier. This shows that incorporating N into GaP barriers is an effective way to achieve desirable wavelength and optical gain.     

Electric subbands in Si/SiGe strained layer superlattices

The subband structure for electrons in Si/SiGe strained layer superlattices along the (100) direction is calculated self-consistently including many-body effects in the local density approximation. The strain induced splitting of the six-fold degenerate conduction band results in different potential wells for different valleys. The charge distribution between the layers and valleys is calculated versus carrier concentration and conduction band offset for different strains. An estimate for the band offsets is obtained by comparison of experimental results with the calculations.     

单频导纳谱法测量锗硅量子阱的能带偏移

提出了用单频导纳谱法测量储硅单量子阶的能带偏移，与常规的多频导纳谱相比，它只需测一个频率的导纳谱就能得到更精确的实验结果。用该方法对Ｓｉ／Ｇｅ_０．３３Ｓｉ_０．６７／Ｓｉ单量子阱进行测试，得到激活能为Ｅ_a＝０．２０ｅＶ。为了计算出能带偏移值，必须能准确确定具有单量子阱结构样品中的费密能级位置，由于在单量子阱结构中费密能级的位置与阱材料、垒材料的掺杂浓度、阱的高度（即能带偏移）及温度等几个因素均有关。为此，本文通过解泊松方程，计算出结合本文样品 关键词：     

A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaN_xAs_yP_(1-x-y)/GaP quantum wells on GaP substrates

The GaP-based dilute nitride direct band gap material Ga（NAsP） is gaining importance due to the monolithic integra- tion of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga（NAsP）/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen （N） concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/Al2Ga1-2P QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and AI into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.     

Band alignment of SiO2/Si structure formed with nitric acid vapor below 500 °C

A relatively thick (i.e., ∼9 nm) SiO₂ layer can be formed by oxidation of Si with nitric acid (HNO₃) vapor below 500 °C. In spite of the low temperature formation, the leakage current density flowing through the SiO₂ layer is considerably low, and it follows the Fowler-Nordheim mechanism. From the Fowler-Nordheim plots, the conduction band offset energy at the SiO₂/Si interface is determined to be 2.57 and 2.21 eV for HNO₃ vapor oxidation at 500 and 350 °C, respectively. From X-ray photoelectron spectroscopy measurements, the valence band offset energy is estimated to be 4.80 and 4.48 eV, respectively, for 500 and 350 °C oxidation. The band-gap energy of the SiO₂ layer formed at 500 °C (8.39 eV) is 0.68 eV larger than that formed at 350 °C. The higher band-gap energy for 500 °C oxidation is mainly attributable to the higher atomic density of the SiO₂ layer of 2.46 × 10²²/cm³. Another reason may be the absence of SiO₂ trap-states.     

Characterization of cubic phase MgZnO/Si(1 0 0) interfaces

The microstructural properties of the Mg_xZn_1−xO/Si(1 0 0) interface were investigated using transmission electron microscopy (TEM) and chemical states of the heterostructure were studied by high resolution X-ray photoelectron spectroscopy (XPS). By analyzing the valence band spectra of thin Mg_xZn_1−xO/Si(1 0 0) heterostructures, the valence band offset between such Mg_0.55Zn_0.45O and Si(1 0 0) was obtained to be 2.3 eV. Using the cubic ternary thin films as insulators, metal-insulator-semiconductor (MIS) capacitors have been fabricated. Leakage current density lower than 3 × 10⁻⁷ A/cm² is obtained under the electrical field of 600 kV/cm by current-voltage (I-V) measurement. Frenkel-Poole conduction mechanism is the main cause of current leakage under high electrical field.     

InP-SiO2 metal-insulator-semiconductor structure parameters investigated with DLTS and other capacitance techniques

In this paper, we report the study of a n-type InP-SiO₂ Metal-Insulator-Semiconductor structure by means of Deep Level Transient Spectroscopy and two complementary techniques : Capacitance versus Voltage and Conductance versus Frequency measurements. We have observed two bulk traps probably related to impurities in the InP crystal. Majority carrier interface states have been studied : the three methods bring similar density profiles showing a minimum value about 10¹² eV^-1 cm^-2 in the energy range 0.4–0.7eV below the conduction band edge. Moreover, we have detected a “missing Phosphorus” interface level at 0.3 eV below the conduction band with a density about 4 x 10¹⁰ cm^-2.     

Valence and conduction band offset measurements in Ni0.07Zn0.93O/ZnO heterostructure

We report valence and conduction band offset measurements in a pulsed laser deposited Ni_0.07Zn_0.93O/ZnO heterostructure using X-ray photoelectron spectroscopy, valence band spectroscopy and ultraviolet visible spectroscopy. Neglecting the strain effect, the valence band offset was estimated to be 0.32 eV and the conduction band offset comes out to be −0.23 eV. Ratio between conduction band and valence band offset is 0.72. Core level shifting due to Ni doping has also been explained. Magnetotransport study of Ni_0.07Zn_0.93O film reveals that the charge carriers might be spin polarized at the interface of the heterojunction.     

Experimental determination of valence band offset at PbTe/Ge(1 0 0) interface by synchrotron radiation photoelectron spectroscopy

The band offset at the interface of PbTe/Ge (1 0 0) heterojunction was studied by the synchrotron radiation photoelectron spectroscopy. A valence band offset of ΔE_V = 0.07 ± 0.05 eV, and a conduction band offset of ΔE_C = 0.27 ± 0.05 eV are concluded. The experimental determination of the band offset for the PbTe/Ge interface should be beneficial for the heterojunction to be applied in new optoelectronic and electronic devices.