Zn0.04Cd0.96Te中深能级的红外光电导谱研究

应用红外光电导谱研究半绝缘p型Zn_0.04Cd_0.96Te中的深能级,在温度从4.2到165K范围内,观察到了位于0.24,0.34,0.38,0.47,0.55和0.80eV处6个光电导响应峰.结合4.2K下光致发光谱的测量结果以及对Zn_xCd_1-xTe中深能级发光光谱、深能级瞬态谱等已有的研究结果,对这些响应峰对应的深能级特性进行了讨论 关键词： xCd_1-xTe')" href="#">Zn_xCd_1-xTe 光电导 杂质 深能级     

K/GaAs(100)表面的氮化

K吸附层的存在能促进GaAs(100)表面在室温下的氮化.光电发射测量为此提供了证据.在将K/GaAs(100)暴露于纯氮以后，价带和芯能级谱均会出现显著变化：功函数有一定程度回升，价带谱中显露N2p峰，Ga2p和As2p芯能级谱中产生化学位移分量.就所研究的三种不同的K覆盖度(1/4，1/2和1ML)而言，1ML的那种显示了最强的促进作用. 关键词：     

A面(11-20)ZnO薄膜中杂质的偏振PL谱研究

本文通过分析A面(11-20)ZnO薄膜的低温PL(光致发光)光谱偏振特性来研究ZnO光致发光谱中杂质峰的来源。低温(4 K)下观察到476、479 nm两处新的杂质峰以及390 nm处激子峰,根据两个杂质峰的偏振特性,初步判定476nm峰来源于氧空位能级到价带轻空穴的跃迁,479 nm峰来源于氧空位价带重空穴的跃迁。     

C_2H_2,C_2H_4与K在Ru(100)表面上共吸附的UPS研究

利用紫外光电子谱 (UPS)对乙烯 (C2 H4)和乙炔 (C2 H2 )气体在Ru(10 10 )表面的吸附及与K的共吸附进行了研究 ,实验结果表明 :当衬底温度超过 2 0 0K ,乙烯即发生脱氢反应后 ,σCH 和σCC 能级均向高结合能方向移动 .在室温下 ,σCH和σCC 能级位置与乙炔在Ru(10 10 )表面的吸附时的分子能级完全一致 .乙烯发生脱氢反应后的主要产物为乙炔 .衬底温度从 12 0K升到室温 ,Ru(10 10 )表面上乙炔的σCH 和σCC 能级均未发现变化 .室温下乙炔仍然可以在Ru(10 10 )表面以分子状态稳定吸附 .在有K的Ru(10 10 )表面上 ,室温时σCC谱峰几乎消失 .碱金属K的存在促进了乙炔的分解 .     

CO在有K沉积的W(100)面上吸附的角分辨紫外光电子能谱

在不同K覆盖度的W(100)面上吸附CO的Hel紫外光电子能谱研究表明:α和β态的CO由于K的影响,吸附状态发生改变,与CO分子态(α态)有关的5σ/1π分子轨道能级随K覆盖度的增加,结合能位置从8.6eV移到9.3eV,反映K出现后,衬底对α-CO分子反施的增强。在与CO分解态(β态)有关的谱峰位置上(结合能为5.5eV)出现两个离散的谱峰,一个在6.0eV左右,另一个在5.2eV左右。其中结合能在5.2eV左右的谱峰强度随K的覆盖度增加而增大,它的能量位置与O在K覆盖的W(100)面上吸附时的能级位置 关键词：     

KCl:Li:Na晶体中的F_A(Ⅱ)—F_B(Ⅱ)心

采用扩散法在KCl:Li:Na晶体中形成了浓度适当、分布均匀的F心.以汞灯进行色心转型,获得了F_A(II)心和F_B(II)心.测量77K时晶体的吸收谱,观察到明显的双峰结构.在相同的温度下测得晶体的荧光谱.F_b(II)心和F_A(II)心的荧光峰分别为2.49μm和2.66μm.采用点离子模型并在离子尺度修正中计入次近邻离子的贡献,计算了KCl晶体F_A(Li)心的非微扰态,然后以微扰法计算了F_A(Li)心的能级位置.计算值与实验值比较,结果令人满意.     

半导体电子态理论简介(Ⅰ)

随着半导体技术和实验手段的发展,半导体理论也相应地得到了发展.早在六十年代,回旋共振和磁光吸收以及半导体浅杂质研究的同时,产生了半导体有效质量理论[1,2].它不仅弄清了半导体能带结构的细节(如导带极小的位置,价带形状的各向异性,有效质量等等),而且能定量地解释了半导体中浅施主、受主能级位置和性质,磁能级等实验结果.七十年代,表面实验技术,包括各种分析测试手段(如低能电子衍射,光电子谱仪等)使人们对半导体表面结构(弛豫、重构),原子吸附,表面、界面电子态等进行了研究.与此同时。半导体中深杂质态性质的研究(包括深能级瞬态谱、…     

GaAs/Al_(0.23)Ga_(0.77)As双量子阱的带边不连续性和阱间耦合

本文报道在300和77K对一组具有不同垒宽Lb的GaAs/Al_(0.23)Ga_(0.77)As双量子阱样品的光调制反射谱(PR)的研究结果。除观察到11H,11L和22H等容许跃迁外,同时还识别一个从Al_(0.23)Ga_(0.77)As价带顶至量子阱第一电子束缚能级的跃迁,另一个从量子阱第一轻空穴束缚能级至Al_(0.23)Ga_(0.77)As导带底的跃迁。利用这些跃迁确定导带边不连续性为0.63。对Lb≤40实验观察到11H和11L跃迁都明显地分裂成对称和反对称分量,对分裂大小的实验值与理论计算作了比较。在77K的11H的PR谱中在高能端明显地出现一个肩形峰,其形状不能用PR标准线形来拟合。如认为它对应于带间跃迁,并由此估计激子的束缚能约为8meV。     

p型硅MOS结构Si/SiO_2界面及其附近的深能级与界面态

用深能级瞬态谱(DLTS)技术系统研究了Si/SiO_2界面附近的深能级和界面态。结果表明,在热氧化形成的Si/SiO_2界面及其附近经常存在一个浓度很高的深能级,它具有若干有趣的特殊性质,例如它的DLTS峰高度强烈地依赖于温度,以及当栅偏压使费密能级与界面处硅价带顶的距离明显小于深能级与价带顶的距离时,仍然可以观测到一个很强的DLTS峰。另外,用最新方法测量的Si/SiO_2界面连续态的空穴俘获截面与温度有关,而与能量位置无明显关系,DLTS测量的界面态能量分布与准静态C-V测量的结果完全不一致。本文提出的Si/SiO_2界面物理模型能合理地解释上述问题。     

苝四甲酸二酐薄膜电子结构的同步辐射共振光电子能谱研究

利用基于同步辐射的近边X射线吸收精细结构谱(NEXAFS)和共振光电子谱(RPES)研究了苝四甲酸二酐分子(PTCDA)薄膜的电子结构.碳K边NEXAFS谱中能量小于290 eV的四个峰对应于PTCDA分子不同化学环境碳原子1s电子到未占据分子轨道的共振跃迁.RPES谱中观察到共振光电子发射和共振俄歇电子发射导致的共振峰结构,以及二次谐波激发的碳1s信号.根据电子动能对入射光能量的依赖性分别对三类峰结构进行了归属.同时,发现PTCDA分子轨道共振光电子峰的强度具有光子能量依赖性.这种能量选择性共振增强效应是由于PTCDA分子轨道空间分布差异导致的.共振俄歇峰主要源于高结合能(4.1 eV)分子轨道能级电子参与的退激发过程.明确RPES实验谱图中各个峰结构的起源有助于准确利用基于RPES的芯能级空穴时钟谱技术定量估算有机分子/电极异质界面处电子从分子未占据轨道到电极导带的超快转移时间.     

Spectral dependence of photoresponse and electronic structure of monocrystal of CuInTe2

The photoconductivity spectrum of a single crystal of the semiconducting compound CuInTe₂ has been experimentally resolved into various distinct peaks at 300 K in the range from 0.6 to 1.5 μ for the first time. The observed peaks are explained on the basis of the transitions originating from the valence sub-band structure. Impurity level is also reflected in the photoconductivity spectrum.     

Photo-induced magnetophonon resonance in n-InSb at 4.2°K

Spin-flip and two-phonon as well as normal magnetophonon resonance are observed in CO₂-laser-irradiated photoconductivity in n-InSb at 4.2°K. The effects are attributed to the resonant cooling of photo-excited electrons due to optical phonon emission.     

Transient photoconductivity associated with the formation of electron-hole droplets in optically pumped germanium

Transient decay properties of photoconductivity of highly excited germanium are investigated at 1.6–4.2 K by use of a pulsed laser with the width of 5 nsec. An anomalous profile is observed in the decay curve of the photocurrent, which is interpreted in terms of the electron-hole droplets model.     

Thermal quenching of the 1–1.35 eV extrinsic photoconductivity in semi-insulating GaAs (Cr,O)

We report in this work, photoconductivity measurements between 77 and 300 K, in semi-insulating GaAs samples doped with chromium and oxygen. These samples exhibit a striking photoconductivity behaviour, which is characterized by a strong increase of the photoconductivity after long time excitation with photons in the 1–1.35 eV spectral range at 77 K. This increase is thermally quenched at 135 K. We explain this anomalous behaviour by means of a generation of traps by light within this spectral range; these photogenerated traps being annealed at 135 K. To our knowledge this is a phenomenon which has not yet been observed in GaAs.     

Phonons in surface photovoltage of GaAs

Oscillatory surface photovoltage is reported in GaAs at 4.2°K, characterized by two series of minima. Dominating series is attributed to the capture of photoexcited electrons by surface states with emission of phonons. Second, weak series coincides with oscillations in photoconductivity.     

Photoconductivity study of a single crystal of GuGaS2 grown by iodine transport

Photoconductivity spectrum of a single crystal of CuGaS₂ has been resolved into various distincts peaks in the range from 0.5 to 0.7 micro. The peaks are explained on the basis of creation of electron-hole pairs and transitions caused by deep centers. The characteristic absorption in the green region is also reflected in the photoconductivity spectrum.     

FAR-INFRARED PHOTOCONDUCTIVITY MECHANISM ON SHALLOW IMPURITY IN GaAs

We report the far-infrared photoconductivity spectroscopy (FIRPCS) of the high purity n-GaAs grown by molecular beam epitaxial (MBE) technique. The current-voltage (I-V) measurement and FIRPCS under different electric field strength have been performed on high purity n-GaAs at 4.2K. Except for photothermal ionization process, a new far-infrared photoconductivity (FIRPC) mechanism is observed. This photo ionization process is assisted by impact ionization and depends on external electric field. This new mechanism originates from photo-field ionization.     

Hole traps in GaSe:Co single crystals

In order to clarigy the nature of the cobalt related hole traps (CRHT) in GaSe single crystals, GaSe:Co single crystals were grown by the Bridgman method and the optical absorption spectra, the photoconductivity spectra and the thermally stimulated current (TSC) were investigated. The energy levels of the CRHT in GaSe:Co single crystals were located at 0.18, 0.28, 0.38, 0.49 and 0.57 eV above the valence band. The optical absorption peaks and the photoconductivity peaks corresponding to the CRHT were observed in the wavelength range from 650 to 950 nm and these peaks are respectively attributed to the carrier transitions from the CRHT to the indirect conduction band of GaSe:Co single crystals.     

Microwave-induced magnetic field state with zero conductivity in GaAs/AlAs Corbino disks and hall bars

The microwave photoconductivity of the 2D electron gas in GaAs/AlAs heterostructures has been investigated at a temperature of 4.2 K in magnetic fields up to 1.5 T. It has been found that the magnetic field state with zero conductivity appears in GaAs/AlAs Corbino disks irradiated by 130.70-GHz microwave radiation. This state was previously observed only in GaAs/AlGaAs Corbino disks with much higher electron mobility and lower density. It has been shown that the microwave photoconductivity measured in high magnetic fields on Corbino disks can significantly differ from the value calculated from the results of the measurements on Hall bars. This difference is explained by the fact that the conditions of the appearing magnetoplasmons that affect the magnitude and character of the microwave photoconductivity (photoresistance) in the Corbino disks are nonequivalent to those in the Hall bars.