光电容法研究电子辐照GaP中的深能级

本文提出含多个深能级响应的光电容瞬态分析方法:在不考虑各能级之间电子、空穴跃迁的条件下,可出“多指数过程分离法”,将总的瞬态过程分离为各能级上指数型瞬态过程之和.运用这一方法,对lMeV(4×1015cm-2电子辐照GaP LED进行了定态和两种注入条件的瞬态光电容测量,观察到H1、H2、H3三个空穴能级(0.51、0.75、1.15eV)和E1、E2、E3、E4四个电予能级(0.68、0.84、0.89、1.01eV),并得到各能级的光离化截面谱.外量子效率及发射谱测量结果表明;电子辐照引入的深能级(H1-H3,E1-E4)表现出无辐射复合中心的性质.     

GaN深中心Zn的低温瞬态研究

本文研究了GaN:Zn的低温瞬态过程,同时测量了衰减中的时间分辨光谱,从两者测量的结果得出:2.89eV的光致发光寿命为300ns(2K).实验证实,Zn作为发光中心的同时也引起一些非辐射陷阱.2.89eV的瞬态曲线可分为两部分,在短时范围(1μs)内基本上是指数形式,可归结为导带中光激发的电子和束缚在ZnGa受主上空穴的复合.在长时范围(t>>1μs)内瞬态曲线则偏离了指数规律,相当好地符合Becqureal经验公式.     

正硅酸锌中能量传递的激子机理

在α型正硅酸锌中,用接近吸收边(Eg～5.5eV)的光能激发,发现了激子能量传递到发光中心的某些特征。在一个弛豫状态上,激子扩散的激活能估计为0.075eV,激子在自局域化前通过的扩散体积为0.5×10-19cm-3。实验确定的磷光体中能量传递的参数可实用于选择最佳颗粒尺寸分布。     

波段外激光辐照光导型InSb探测器的一种新现象

利用不同功率密度的10.6 μm(光子能量为0.12 eV)连续激光辐照了禁带宽度为0.228 eV的光导型锑化铟探测器, 得到了与以往报道不同的实验现象. 当10.6 μm波段外激光辐照光导型探测器时, 探测器吸收激光能量后温度升高. 在探测器的温升过程中, 存在一个转变温度T₀. 当探测器的温度T<T₀时, 载流子浓度基本不变, 迁移率随温度的升高呈T^-2.35趋势下降, 引起探测器的电导率减小, 电阻增大, 响应输出电压升高; 当T>T₀时, 热激发载流子浓度随温度的升高呈指数增长, 电阻急剧下降, 超过了载流子迁移率降低对电阻的影响, 响应输出急剧下降. 光电导探测器在较高功率密度波段外激光辐照下的响应特性是载流子的浓度和迁移率在温度影响下相互作用的结果. 这对进一步完善半导体内载流子输运模型提供了实验依据.     

双异质结AlxGa1-xAs/GaAs发光管中与氧有关能级的测量

用DLTS和单次脉冲瞬态电容技术研究了液相外延生长的双异质结AlxGa1-xAs/GaAs发光管,掺Si的n-Al0.05Ga0.95As有源层中的深能级。着重分析了一个与氧有关的电子陷阱,其发射激活能为EC-ED=0.29eV。我们发现该电子陷阱随正向注入脉冲宽度tp的增加DLTS峰向低温移动,即在确定的温度下发射率随tp的增加而增加。用DLTS首次测得该能级的俘获瞬态谱,发现俘获峰随反向撤空脉冲宽度tR的增加向低温端移动,即在确定的温度下俘获率随tR的增加而增加,并且俘获激活能从△Eσ=0.28eV变化到0.26eV,用位形坐标图讨论了引起变化的原因。     

p型α-多孔SiC的光致发光光谱研究

用UV光照射和不用UV条件下形成的p型α-PSC的PL光谱，2.35eV，2.50eV和2.70eV及3.4eV附近的发射峰已被观察到.研究了不同的制备条件下形成的p型α-PSC的PL谱的稳定性和不同的能量的光激发引起PL谱的差别.结果表明，在电化学腐蚀过程中制备条件对PSC的PL谱有很大的影响，前者在低能区有较强的光发射而后者则在高能区有较强的光发射；前者的光谱稳定性较好而后者发射光谱强度则随时间的增加而减少.对产生这些差别的原因进行了深入讨论. 关键词：     

光化学和光生物学中的微微秒闪光光解和光谱

我们研制了一种微微秒闪光光解的装置,能用照相记录探索性研究中瞬变的中间物的光谱,可以和用光导摄像管、光多道分析器对400～950nm范围内任何一个波长进行详细动力学研究的装置联用。样品被波长为530,694或1060nm,5～8ps(微微秒)间隔的单个光脉冲激发,并用也是微微秒间隔的时期—延迟连续脉冲控制。在几个微微秒到几个毫微秒的范围内,时间分辨力可以达到±4微微秒。     

软X光平面镜反射率标定实验

报道了掠入射软X光平面镜反射率标定实验。实验利用北京同步辐射装置 (BSRF) 3W 1B束线及反射率计靶室 ,在束流 35mA～ 110mA、贮存环电子能量 2GeV专用光运行模式下 ,在 5 0eV～ 85 0eV能区分四个能段 ,进行了 5°掠入射Ni平面镜反射率标定实验。标定过程中用高灵敏度无死层的硅光二极管代替X射线二极管作探测器 ,输出信号提高 2～ 3个量级 ,可标定能区从 15 0eV～ 2 70eV拓展到 5 0eV～ 85 0eV ,给出了完整的 5°Ni平面镜反射率标定曲线。最后把实验数据与理论计算作了比对并进行了分析。     

HVPE外延GaN膜中黄带的光致发光激发谱研究

测量了氢化物气相外延方法生长的非特意掺杂和掺碳GaN外延膜的光致发光谱，并在光致发光谱峰位2．25eV(550nm)附近分别测量了光致发光激发谱，对两者进行了比较．从光致发光谱中发现掺碳使黄带明显增强，从光致发光激发谱中看到了掺碳引起的约3．38～2．67eV(367～465nn)范围内的特征激发带．利用CC曲线模型说明了特征激发带和黄带之间的关系，分析了黄带的可能起因．     

氢化非晶碳薄膜的光致发光线型及其激发能量依赖关系

本文报道了氢化非晶碳薄膜在2.9-4.5eV光激发下的发光谱。它的光致发光谱是无结构的不对称宽带,半宽度约为0.8eV。在低于3.56eV的光激发下,谱带的峰值能量随激发能量的降低明显红移。在安德森带结构和指数分布的带尾态密度的基础上,考虑了尾态中粒子的两种跃迁过程,实验的PL谱就可得到解释。并用这个简单模型计算了这种材料的光致发光谱特征。     

Incorporation of deep centres in VPE GaAs

The incorporation of deep levels in high purity vapour phase epitaxy (VPE) GaAs is studied as a function of the crystal growth conditions. Two deep levels, at 0.4 eV and 0.75 eV above the valence band, are investigated using photocapacitance. It is shown that their concentrations are always equal and vary together as a function of the AsCl₃ mole fractionX. Two regimes are observed, respectively, characterized by different variations of the total deep level concentrationN _T:N _TαX for lowX, andN _TαX⁻² for highX. In this last range,N _T andN _D are found to vary similarly. This work has been supported by the DRME.     

Photocapacitance study of deep centers in ZnSe-based radiating structures

The photocapacitance method is used to study ZnSe-Au and ZnSe-ZnO(SiO₂) barrier structures in order to investigate deep centers in ZnSe crystals annealed in liquid zinc and subjected to additional thermoprocessing in a vacuum. The energy levels of the deep centers producing photocapacitance are determined. In crystals annealed for 4.5 h acceptor levels with ionization energies of 0.28, 0.36, 0.58, and 0.71 eV are found. With increase in anealing period to 100 h only the level with ionization energy of 0.58 eV appears, leading to a decrease in intensity of the yellow-green band and an increase in intensity of blue scintillation in the electroluminescence spectra.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 59–63, July 1984.     

判别两个或两个以上深能级是否属于同一中心的方法

本文分别研究了两个或两个以上深能级之间的耦合和非耦合两种情况所对应的光电容瞬态,根据这两种瞬态的本质差别,提出一个判别两个或两个以上深能级是否属于同一深中心的方法。它具有适用于两个以上的多个深能级的样品以及方法简单和测量时间短等优点。作为例子,将它应用于判别硅中和金有关的施主和受主两能级,结果证实它们确实是属于和金有关的同一中心,而不是分属于两个中心。 关键词：     

Evidence for two energy levels associated with EL2 trap in GaAs

By photocapacitance technique, applied to n-type LEC-grown GaAs, two energy levels:E _v +0.45 eV andE _c –0.75 eV are identified, for the first time, as being associated with the EL2 trap. As follows from the analysis of photo-EPR results on highly resistive GaAs crystals, the same energy levels can be attributed to the arsenic antisite defect, As_GA. In view of these findings, it is argued that the occupied EL2 level corresponds to the neutral charge state of As_Ga defect.     

Double correlation technique (DDLTS) for the analysis of deep level profiles in semiconductors

A very sensitive technique is presented which can be applied to determine deep level profiles in space-charge layers of Schottky barriers orpn-junctions. The method uses an extended transient capacitance technique with correlation similar to Lang's DLTS technique. The extension of DLTS to double correlation DDLTS is necessary to resolve the deep level profile and to exclude the field dependence of the capture cross-section and contact effects. By using a double-pulse capacitance transient and correlation, these undesired effects can be subtracted. Profiles can be determined for deep levels at concentrations 10⁴ times lower than the background doping. Results are reported for epitaxial GaAs which showed one major deep level at 0.18 eV below the conduction band. Near the interface to the substrate, a slight shift in energy from 0.18 to 0.19 eV is observed. A second level at 0.43 eV decays into the epi-layer in the form of a diffusion tail.     

On the Spatial Density Matrix for the Centre of Mass of a One-Dimensional Perfect Gas

We examine the reduced density matrix of the centre of mass on position basis considering a one-dimensional system of Nnoninteracting distinguishable particles in a infinitely deep square potential well. We find a class of pure states of the system for which the off-diagonal elements of the matrix above go to zero as Nincreases. This property holds also for the state vectors which are factorized in the single particle wave functions. In this last case, if the average energy of each particle is less than a common bound, the diagonal elements are distributed according to the normal law with a mean square deviation which becomes smaller and smaller as Nincreases towards infinity. Therefore when the state vectors are of the type considered we cannot experience spatial superpositions of the centre of mass and we may conclude that position is a preferred basis for the collective variable.     

Characterization of N-doped ZnO layers grown on (0 0 0 1) GaN/Al2O3 substrates by molecular beam epitaxy

We investigated the optical properties and electrical properties of N-doped ZnO layers grown on (0 0 0 1) GaN/Al₂O₃ substrates by molecular beam epitaxy, employing 10 K photoluminescence (PL) measurements, current–voltage (IV) measurements, capacitance–voltage (CV) measurements, and 100 K photocapacitance (PHCAP) measurements. 10 K PL spectra showed that excitonic emission is dominant in N-doped ZnO layers grown after O-plasma exposure, while overall PL emission intensity is significantly reduced and deep level emission at around 2.0 2.2 eV is dominant in N-doped ZnO layers grown after Zn exposure. IV and CV measurements showed that N-doped ZnO layers grown after Zn exposure have better Schottky diode characteristics than O-plasma exposed samples, and an N-doped ZnO layer grown at 300 °C after Zn exposure has best Schottky diode characteristics. This phenomenon is presumably due to lowered background electron concentration induced by the incorporation of N. PHCAP measurements for the N-doped ZnO layer revealed several midgap trap centers at 1.2 1.8 eV below conduction band minimum.     

GaAs1-xPx中混晶无序与Fe深中心的性质

对不同组分的掺FeⅢ-Ⅴ族混晶GaAs1-xPx,测量了Fe深受主中心空穴热发射的非指数恒温暗电容瞬态及DLTS谱。用混晶无序使Fe深能级展宽的模型理论拟合实验结果,得到Fe能级Gauss型展宽的半宽和中心能级的热发射率,并确定出基态空穴跃迁的中心能级的焓变与组分的关系:先是减少,而后增大,与由光电容方法得到的Gibbs自由能变量与组分x的关系明显不同。 进一步讨论表明,上述两种测量方法得到的Fe中心的激活能不同,可能反映Fe中心的键合状态和混晶无序诱导的品格弛豫的影响。     

Electronic properties and deep level transient spectroscopy of CdS/CdTe thin film solar cells

It is well known that preparing temperatures and defects are highly related to deep-level impurities. In our studies, the CdTe polycrystalline films have been prepared at various temperatures by close spaced sublimation (CSS). The different preparing temperature effects on CdS/CdTe solar cells and deep-level impurities have been investigated by I--V and C--V measurements and deep level transient spectroscopy (DLTS). By comparison, less dark saturated current density, higher carrier concentration, and better photovoltaic performance are demonstrated in a 580oC sample. Also there is less deep-level impurity recombination, because the lower hole trap concentration is present in this sample. In addition, three deep levels, E_v+0.341 eV(H4), E_v+0.226 eV(H5) and E_C-0.147 eV(E3), are found in the 580oC sample, and the possible source of deep levels is analysed and discussed.