透射阴极射线发光——用于研究块状半导体中缺陷的扫描电子显微镜新技术

我们报告一种用电子显微镜研究缺陷的新方法,这种方法是已知的阴极射线发光方法的扩展。在这种我们称之为透射阴极射线发光的新技术中,由于扫描电子显微镜(SEM)电子束的作用,在厚的半导体样品的顶部表面产生发光,这个发光被用来探测发光区域下面的样品体积。用安装在样品下面的小的固体检测器收集透射的发光强度,并且显示在SEM的阴极射线管上。我们用显示GaAs衬底和GaAlAs外延层中的位错来说明这种技术的用途。     

驱动电压频率对固态阴极射线发光影响的研究

固态阴极射线发光(SSCL)是发光学中一种新的激发方式,引发出一些发光学中的重要问题,但是固态阴极射线发光的性质还不是十分清楚,需要进一步研究。文章用SiO₂作为电子加速层, 有机材料MEH-PPV为发光层, 在正弦交流电压驱动下实现了固态阴极射线发光,得到410和580 nm两个发光峰。通过研究这两个发光峰的性质,证实它们分别符合能带理论和分子理论。改变驱动电压的频率时,长波峰的发光强度随频率的增加而增加,而短波峰的发光强度随频率的增加而减小,这是由于这两个发光峰对应的上能级寿命不同引起的。     

深能级对GaAs1-xPxLED老化过程的影响

用深能级瞬态谱(DLTS)研究了GaAs1-xPx LED在正向电压,I=100mA(J=250A/cm2)大电流下老化750小时左右的过程中深能级浓度、深度、俘获截面的变化。GaAs1-xPx LED中存在三个电子能级:△En1=(0.19±0.01)eV;△En2=(0.20±0.01)eV;△En3=(0.40±0.01)eV。发现老化之后△En1与△En2的能级密度变小,而△En3的能级宽度却有所增大。同时测量了它们的发光光谱、光通,C-V特性和I-V特性。讨论了深能级在GaAs1-xPx LED老化过程中对发光效率与退化特性的影响。认为△En1与△En2对GaAs1-xPx LED的发光效率与退化特性无影响,而△En3是限制GaAs1-xPx LED发光效率和退化特性的有效复合中心。     

阴极射线致发光形貌术──一种研究晶体缺陷的新工具

一、引 言 固体发光根据其不同的激发方法,分为光致发光、场致发光、阴极射线致发光、化学发光、摩擦发光、辐射发光等.阴极射线致发光就是高速运动的电子打在稠密的物质上而发出光的现象.1879年,Crookes[1]首先应用阴极射线致发光现象观察多种矿物.自此以后,一个相当长时期,这     

GaN外延层中的缺陷对光学性质的影响

用金属有机化合物气相外延（ＭＯＶＥＰ）方法生长具有不同表面形貌的非掺杂ＧａＮ，并对部分样品的外延层表面进行镜面加工．用阴极射线发光、光散射和拉曼散射方法观察ＧａＮ中深能级发光、缺陷散射光分布和拉曼散射光频移．结果表明，缺陷不但影响ＧａＮ的发光和光散射，而且影响拉曼频移     

高温氧化多孔硅的电子束辐照效应

通过高温氧化处理得到的多孔硅,其阴极射线发光谱呈现明显的三峰结构。峰强随电子束辐照时间而下降。对光致发光很弱的样品,电子束辐照后光致发光明显地增强。红外透射谱及Raman谱分析表明样品基本上成为SiO_x.进一步分析指出三峰可能来源于SiO_x中的缺陷中心发光。电子束辐照在SiO_x禁带中引进了一些缺陷能级,通过这些能级使得紫外线可激发样品发光,出现光致发光增强的现象。     

声表面波对GaAs(110)量子阱发光特性的调制

结合声表面波和光致发光谱在低温(15K)下对非故意掺杂的GaAs(110)量子阱结构的发光特性进行了研究.实验结果表明，由于声表面波的作用GaAs(110)量子阱的发光强度减弱,并且其对应的重空穴能级出现了分裂的现象，当施加的声波强度P_rf达到20dBm时，能级分裂ΔE达到了10meV.进一步讨论了声表面波对GaAs(110)量子阱圆偏振光自旋注入的影响. 关键词： 发光 GaAs量子阱 声表面波 自旋极化     

固态阴极射线发光的发现

通过分层优化方案，采用有机场致发光材料，发现了一种新的激发发光方式，即固态阴极射线发光（solid state cathodoluminescence，简称SSCL），文章主要介绍了固态阴极射线发光的发现历史、发光现象的辨认、发光现象的普适性考察以及其良好的发展前景．     

非掺杂ZnO薄膜中紫外与绿色发光中心

用直流反应溅射方法在硅衬底上淀积了ZnO薄膜,测量它们的光致发光(PL)光谱,观察到两个发光峰,峰值能量分别为3.18(紫外峰,UV)和2.38eV(绿峰).样品用不同温度分别在氧气、氮气和空气中热处理后,测量了PL光谱中绿峰和紫外峰强度随热处理温度和气氛的变化,同时比较了用FP-LMT方法计算的ZnO中几种本征缺陷的能级位置.根据实验和能级计算的结果,推测出ZnO薄膜中的紫外峰与ZnO带边激子跃迁有关,而绿色发光主要来源于导带底到氧错位缺陷(O_Zn)能级的跃迁,而不是通常认为的氧空 关键词： ZnO薄膜 热处理 光致发光光谱 缺陷能级     

In/GaAs(111)界面形成过程的电子能谱研究

用光电子能谱结合LEED图样分析的方法研究了In在非解理的GaAs(111)面上的界面形成过程。观察到在这一过程中三维In集团的生长起支配作用。发现对于所有研究过的n型样品,包括Ga终止的GaAs(111)-A面和As终止的GaAs(111)-B面,淀积In之前的表面费密能级均在VBM上面0.75±0.05eV处,在淀积过程中迅速移至VBM上面0.90±0.05eV处。 关键词：     

Photoluminescence studies of vacancies and vacancy-impurity complexes in annealed GaAs

Photoluminescence measurements made at various depths below the surface of annealed GaAs single crystals are compared with vacancy distribution profiles obtained from electrical measurements. Results on undoped n-GaAs indicate that isolated Ga or As vacancies form non radiative centers. A broad-band emission at 1.20 eV, arising from V_Ga-donor complexes, is observed in spectra taken from n-type samples doped with Si, Sn or Te. The intensity of the 1.20eV band varies with depth and reaches its maximum value in the region where Ga vacancies are dominant. These results show the consistency between photoluminescence and electrical measurements. A band at 1.37eV has previously been assigned to V_As-acceptor complexes. This band was observed in this study only when the samples had been annealed in ampoules prepared from quartz containing traces of Cu. It is concluded that the 1.37eV band is due to Cu contamination rather than V_As-acceptor complexes.     

Study of n type porous GaAs by photoluminescence spectroscopy: Effect of the etching time on the deep levels

Photoluminescence (PL) analysis is used to study porous layers elaborated by electrochemical etching of n⁺ Si-doped GaAs substrate with different etching times. Temperature and power dependence photoluminescence (PL) studies were achieved to characterize the effect of the etching time on the deep levels of the n⁺ Si-doped GaAs. The energy emission at about 1.46 eV is attributed to the band-to-band (B-B) (e-h) recombination of a hole gas with electrons in the conduction band. The emission band is composed of four deep levels due to the complex of (V_AsSi_GaV_Ga), a complex of a (Ga vacancy - donor - As vacancy), a (Si_Ga-V_Ga³⁻) defect or Si clustering, and a (gallium antisite double acceptor-effective mass donor pair complex) and which peaked, respectively, at about (0.94, 1, 1.14, and 1.32 eV). The PL intensity behavior as function of the temperature is investigated, and the experimental results are fitted with a rate equation model with double thermal activation energies.     

Optical investigation of ferromagnetic Ga1−xMnxN layers grown on sapphire (0 0 0 1) substrates

We have investigated the temperature-dependent photoluminescence (PL) spectra in Ga_1−xMn_xN layers (where x≈0.1–0.8%) grown on sapphire (0 0 0 1) substrates using the plasma-enhanced molecular beam epitaxy technique. All the layers doped with manganese exhibited n-type conductivity with Curie temperature over 350 K. The efficient PL are peaked in the red (1.86 eV), yellow (2.34 eV), and blue (3.29 eV) spectral range. It was found that the blue band at 3.29 eV is mostly associated with the formation complexes between donors (e.g., N vacancy) and Mn acceptors, which results in forming donor levels at 0.23 eV below the conduction band edge. The yellow band is attributed to intrinsic gallium defects. The broad band at 1.86 eV is attributed to inner ⁵D state transition (T₂ to E) of Mn ions.     

GaAs衬底上生长的GaInP_2外延单晶薄膜的杂质污染研究

各种外延技术已被用来在ＧａＡｓ衬底上生长ＧａｘＩｎ１－ｘＰ外延单晶薄膜（ＧａＩｎＰ２／ＧａＡｓ）．很多文献认为,在ＧａＩｎＰ２／ＧａＡｓ生长过程中会被Ｃ杂质污染．我们用高灵敏的ＣＡＭＥＣＡＩＭＳ４Ｆ型二次离子质谱仪直接测量的结果表明,污染ＧａＩｎＰ２／ＧａＡｓ的微量杂质是Ｓｉ,而不是Ｃ．由ＧａＩｎＰ２／ＧａＡｓ在１．１７ｅＶ附近的光致发光峰的峰值随激发强度的变化形状表明了它应属于施主－受主对复合发光．进一步分析表明,施主为处在Ｇａ格位上的Ｓｉ杂质（ＳｉＧａ）,受主为Ｇａ空位（ＶＧａ）．     

The decay of luminescence in natural and silver-doped quartz after X-ray excitation

It is well known that X-rays cause luminescence in quartz. This luminescence consists of two broad bands at 2.5 and 3.3 eV. After X-ray excitation natural quartz has an afterglow. The duration of this afterglow and the intensity of the emitted light show a strong dependence on the temperature of the sample. While the intensity is not so reproducible, the duration of the afterglow has a clear temperature- dependence and can be connected with two electron-traps in the customary band model — one with a depth of 8 meV and the other with 260 meV — using an Arrhenius-plot. If the quartz crystal has been doped with silver by electro-diffusion, additional luminescence bands at 2.2 eV and around 5 eV occurs. The latter broad luminescence band consists of a dominant part with a decay-time of 40 μsec at 4.8 eV and a weak band at 5.4 eV without afterglow. In contrast to natural quartz, the luminescence intensity as well as the decay-time in the silver-doped sample is independent of the temperature in the range 77–300 K. This constant afterglow is associated with partially forbidden transitions in the silver dopant and energy-transfer to the luminescence centres. In the suggested luminescence model, the observed luminescence bands are connected with an energy transition in the silver.     

The I.R. photoluminescence emission band in ZnO

Measurements of emission spectra, excitation spectra, intensity dependence of the luminescence, decay of the luminescence, and temperature dependence of the luminescence in ZnO are reported. The results for the emission at 1·70 eV, with the exception of the decay of the luminescence, were found to be similar to those of the yellow (2·02 eV) emission band in ZnO. Both bands could be excited at the band edge and directly, the intensity of both bands was found to be linear with excitation strength and the asymptotic regions of the temperature dependence of both bands could be approximated by exponential functions. It is proposed that the luminescent transition is an electron transition from the edge of the conduction band to a hole trapped in the bulk at 1·60 eV above the edge of the valence band, and that the luminescence center is an unassociated acceptor-like center.     

二维缺陷GaAs电子结构和光学性质第一性原理研究

采用基于密度泛函理论的第一性原理方法计算了存在Ga空位缺陷和掺杂B原子的二维GaAs的能带结构、态密度和光学性质.计算结果表明空位缺陷二维GaAs显示出金属特性,B原子的引入使体系变为间接带隙半导体,禁带宽度为0.35 eV.态密度计算发现体系低能带主要由Ga的s态、p态、d态和As的s态、p态构成;高能带主要由Ga和As的s态、p态构成.掺杂B原子与存在空位缺陷的二维GaAs相比,静态介电常数相对较低,变为8.42,且易于吸收紫外光,在3.90～8.63 eV能量范围具有金属反射特性,反射率达到52%.     

PbWO4闪烁晶体的发光动力学模型

在对PbWO₄闪烁晶体的光谱特性、发光衰减及其温度依赖以及热释光的研究基础上,并结合理论计算,提出了PbWO₄晶体发光的动力学模型,给出了PbWO₄晶体的基本能带结构及激子发光中心能态、陷阱能级在能隙中的位置。用此模型可以完整说明PbWO₄的发光过程,特别是导致室温下发光效率低的原因。最后还对其主发射成分蓝、绿发光中心的起源作了简要讨论。     

Photoluminescence of a silver-doped glass

The absorption, emission and excitation spectra of Ag⁺ ions in a soda lime glass doped with two different concentration of silver are investigated. Absorption spectra exhibit a main broad band peaked at about 260 nm (4.77 eV) with a shoulder at about 227 nm (5.46 eV). The relative height of the shoulder depends on silver concentration in the glass. Emission spectra of Ag⁺ are dominated by an ultraviolet broad band at about 330 nm (3.76 eV). The excitation spectra for this emission show a preponderant broad band peaked at about 227 nm (5.46 eV) which coincides with peak position of the shoulder displayed in the optical absorption spectra. A weak broad featureless emission band centred at about 550 nm (2.25 eV) with an excitation peak at about 242 nm (5.12 eV) is tentatively related to an impurity from the host silica glass rather than originated in silver-type centres. Comparison of the luminescence decay curves for both emissions show substantial differences between them. Consequently, the emissions in the time-resolved spectra can easily be discriminated.     

Low temperature photoluminescence study of Ga As defect states

Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV,1.476 eV,1.326 eV peaks deriving from 78 meV Ga_(As) antisite defects,and 1.372 eV,1.289 eV peaks resulting from As vacancy related defects.Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states.The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.