GaAs中缺陷的光致发光研究

用光致发光技术研究了未掺杂半绝缘砷化镓中的深能级缺陷,观察到一系列与其有关的光致发光.其中0.69eV发射带是源自EL2的辐射复合发光,0.77eV带是由导带至As_(Ga)施主能级的跃迁.认为1.447eV和1.32eV荧光带系分别对应于与Ga_(As)的两个电子态(38meV和203meV)有关的辐射复合.     

LEC GaAs中缺陷的光致发光研究

本文用4.2K光致发光研究了LEC GaAs的热感生缺陷.热退火时样品分别为无包封,包封或用一个未掺杂的SI-GaAs片覆盖.退火温度为650-850℃,退火在不同气氛下进行(真空,H_2,N_2,H_2+N_2或H_2+As_2). 与缺陷有关的发光带有1.443eV,1.409ev和0.67eV发光带.1.443eV发光带不仅在富Ga的GaAs中出现,而且在富As的热稳定性好的SI-GaAs晶体并经过850℃(在H_2中)热退火的样品中也观测到此发光带.这可能是在退火过程中促进反位缺陷GaAs的形成.1.443eV发光带与GaAs有关.GaAs晶体在H_2中退火后1.409eV峰很强,但在真空中退火末探测到此发光带.文中提出它可能是热退火时氢原子扩散到GaAs晶体中并与某些缺陷结合成络合物的新观点.     

三维光子晶体中的缺陷研究

利用传输矩阵方法研究面心立方结构的三维光子晶体,分析了当其分别存在点缺陷、线缺陷、面缺陷时的传输特性变化,发现当引入点、线、面缺陷后,光子晶体中出现缺陷模,进一步数值计算研究表明缺陷模的出现频率和透过率等特性与缺陷介质球的半径、介电常数和缺陷出现的位置等诸多因素有关,这些结果将有助于光子晶体波导、滤波器等器件的设计和应用.     

一维缺陷光子晶体多个禁带中的窄带缺陷模

用特征矩阵法研究了一维缺陷光子晶体的透射谱。结果发现:在一维缺陷光子晶体的透射谱中的多个禁带内都有窄带缺陷模,窄带缺陷模的波长越大,其宽度越大;当入射角增大后,波长越长的窄带缺陷模的强度变化越小,位置向短波方向移动越多,且S偏振光与P偏振光的窄带缺陷模的分离越大;增大一维缺陷光子晶体中周期性介质的厚度,窄带缺陷模的波长和移动的范围都增大。本研究对一维缺陷光子晶体的窄带缺陷模的选择使用具有重要意义。     

立方相Al_xGa_(1-x)N/GaAs(100)的光致发光研究

本文通过光致发光（ＰＬ）测试发现了ＮＨ３流量的大小对以ＧａＡｓ（１００）为衬底生长立方相ＡｌｘＧａ１－ｘＮ晶体性质的影响的规律,ＮＨ３流量愈少,立方相ＡｌＧａＮ的纯度愈高,而且,其发光峰的位置向短波长方向移动．在同一样品中,ＮＨ３气流的下游的晶体纯度高于上游,而且其发光峰的位置向短波长方向移动．选择合适的生长条件,制备出纯度较高的立方相ＡｌｘＧａ１－ｘＮ晶体,并对实验结果进行了简单的讨论     

注硅不掺杂半绝缘GaAs中的深能级缺陷

用DLTS法对经两步快速热退火(RTA)后的注硅不掺杂SI-GaAs中的缺陷进行了研究。确定了激活层中存在着两个电子陷阱组(以主能级ET1、ET2标记)及其电学参数的深度分布。在体内,ET1=Ec0.53eV,n=2.310-16cm2;ET2=Ec0.81eV,m=9.710-13cm2;密度典型值为NT1=8.01016cm-3,NT2=3.81016cm-3;表面附近,ET1=Ec0.45eV,NT1=1.91016cm-3;ET2=Ec0.71eV,NT2=1.21016cm-3,分别以[AsiVAs,AsGa]和[VAsAsiVGaAsGa]等作为ET1和ET2的缺陷构型解释了它们在RTA过程中的行为。     

含有多缺陷的光子晶体中的局域缺陷模

采用紧束缚法,研究含有缺陷的光子晶体中的缺陷模,导出了缺陷模频率方程。作为特例,采用转移矩阵法,数值计算了含有三个缺陷的一维光子晶体的透射谱和与光子带隙中缺陷模频率对应的光场强度分布,讨论了缺陷间的相互作用对缺陷模的影响。结果表明:当光通过含有多个半波缺陷的光子晶体时,在透射谱的禁带中出现缺陷模,缺陷模的数目与半波缺陷数目相同,而缺陷模频率的间隔随着半波缺陷间隔层数的增加而减小,最后形成一个缺陷模通带;与缺陷模频率对应的光场分布为局域状态,并发现局域光场峰值出现在缺陷邻近层。     

MBE高掺杂n-GaAs:Si和p-GaAs:Be的光致发光谱

我们对MBE高掺杂的n-GaAs∶Si和p-GaAs∶Be进行了光致发光研究,详细比较了高掺杂n-GaAs和p-GaAs在光谱线型,峰值半宽,峰值位置等方面的差异,以及两者的发光与温度的关系.由分析得出,对于高掺杂的n-GaAs,填充在导带内较高能态(K≠0)的电子与价带顶(K=0)空穴的非竖直跃迁是主要的发光过程.而对于高掺杂的p-GaAs,则是以导带底附近(K(?)0)的电子和价带顶附近(K(?)0)的空穴竖直跃迁为主要发光过程.     

温差电致冷元件损伤层探索

通过探索温差电致冷元件的损伤层，提出“平均电导率”等概念。     

空间生长GaAs单晶做衬底的GaAs/AlGaAs DH激光器

我们首次用在中国返地卫星上生长的Si-GaAs单晶做衬底,成功地研制出室温CW工作的GaAs/AlGaAs质子轰击条形DH激光器,DH外延片是用LPE法生长的。激光器的最低阈电流20mA,激射波长857nm,输出功率可达30mW。     

Defect state assisted tunneling in intermediate temperature molecular beam epitaxy grown GaAs

Current transport in molecular beam epitaxy (MBE) GaAs grown at low and intermediate growth temperatures is strongly affected by defects. A model is developed here that shows that tunneling assisted by defect states can dominate, at some bias ranges, current transport in Schottky contacts to unannealed GaAs material grown at the intermediate temperature range of about 400°C. The deep defect states are modeled by quantum wells which trap electrons emitted from the cathode before re-emission to semiconductor. Comparison of theory with experimental data shows defect states of energies about 0.5 eVbelow conduction band to provide the best fit to data. This suggests that arsenic interstitials are likely to mediate this conduction. Comparison is also made between as-grown material and GaAs grown at the same temperature but annealed at 600°C. It is suggested that reduction of these defects by thermal annealing can explain lower current conduction at high biases in the annealed device as well as higher current conduction at low biases due to higher lifetime. Quenching of current by light in the as-grown material can also be explained based on occupancy of trap states. Identification of this mechanism can lead to its utilization in making ohmic contacts, or its elimination by growing tunneling barrier layers.     

MoCVD生长重掺碳GaAs

以四氧化碳(CCl_4)为掺杂剂进行了MOCVD生长掺碳GaAs的研究。p-GaAs外延层的最高空穴浓度可达1.8×10~(20)/cm~3,相应的迁移率为37cm~2/V.s。在重掺杂p-GaAs外延层中出现明显的能带收缩和晶格失配。     

A comparison between atomic concentration profiles and defect density profiles in GaAs annealed after implantation with beryllium

Semi-insulating chromium-doped GaAs was implanted with 100 keV Be ions to fluences of 5 × 10¹³ and 1 × 10¹⁵ ions/cm². Specimens were annealed at 800°C for thirty minutes. Beryllium atomic concentration profiles, as determined by secondary ion mass spectrometry (SIMS), were compared to the defect density profiles obtained from transmission electron stereomicroscopy techniques for the annealed samples. A major redistribution of Be was observed compared to the as-implanted distribution after annealing at the higher fluence, whereas only a slight redistribution of Be occurred for the lower fluence. A major difference in the defect density profiles was observed with the fluences used for this study in the region where the annealed specimens were compared. The distribution of defects throughout the implanted-annealed layer was examined in GaAs annealed after implantation with the higher fluence using sectioned specimens. The relationships between the atomic Be concentration profile, the defect density profile, and the distribution of some specific defects were compared in these sectioned layers. The distribution and size of defects appear to be directly influenced by the Be concentration and its associated implantation induced damage.     

P－GaP中离子注入缺陷的形成

研究了Ｚｎ~＋离子注入ｐ－ＧａＰ半导体所引起的缺陷。在电流密度为０．０３μＡ／ｃｍ~２下，将注入Ｚｎ~＋离子剂量为１×１０１~（１４）离子／厘米~２的ＧａＰ样品腐蚀出蚀坑后用ＳＥＭ观察，结果表明，在离子注入区域有缺陷形成。     

Uniform intermixing of quantum wells in p-i-n modulator structures by impurity free vacancy diffusion

We present the results of an investigation of impurity free vacancy diffusion (IFVD) post-growth treatments of p-i-n modulator structures. The investigation is in two parts. We first establish that gallium vacancies (V_Ga) are produced during IFVD (by measuring the intensity of the low temperature 1.2 eV signal from Si-V_Ga complexes) in a thick Si-doped GaAs sample. The second part of this work investigates the degree of intermixing of three 80Å GaAs quantum wells embedded in the intrinsic region of a p-i-n modulator at depths between 1–2 μm from the surface. Photoluminescence studies on etched samples and cathodoluminescence showed that no significant depth dependence occurs as a result of IFVD.     

Defect characterization of Tl4GaIn3Se2S6 layered single crystals by photoluminescence

Photoluminescence (PL) spectra of Tl₄GaIn₃Se₂S₆ layered crystals grown by the Bridgman method have been studied in the energy region of 2.02–2.35 eV and in the temperature range of 16–45 K. A broad PL band centered at 2.20 eV was observed at T=16 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.1 to 149.9 mW cm⁻² range. Radiative transitions from shallow donor level located at 10 meV below the bottom of conduction band to moderately deep acceptor level located at 180 meV above the top of the valence band were suggested to be responsible for the observed PL band. An energy level diagram showing transitions in the band gap of the crystal was plotted taking into account the results of present work and previously reported paper on thermally stimulated current measurements carried out below room temperature. Analysis of the transmission and reflection measurements performed in the wavelength range of 400–1030 nm at room temperature revealed the presence of indirect transitions with 2.22 eV band gap energy.