高组份Al值的AlxGa1-x As和AlxGa1-x As/GaAs/AlxGa1-xAs/GaAs多层结构的MOCVD生长

用自制常压MOCVD系统,在半绝缘GaAs衬底上生长高Al组份Al_xGa_1-xAs（其x值达0.83）,和Al_xGa_1-xAs/GaAs/Al_xGa_1-xAs/GaAs多层结构,表面镜面光亮。生长层厚度从几十到十几μm可控,测试表明外延层晶格结构完整,x值调节范围宽,非有意掺杂低,高纯GaAs外延层载流子浓度n_300K=1.7×10¹⁵cm^-3,n_77K=1.4×10¹⁵cm^-3,迁移率μ_300K=5900cmcm²/V.S,μ_77K=55500cm²/V.S。用电子探针,俄歇能谱仪测不出非有意掺杂的杂质,各层间界面清晰平直。 对GaAs,AlGaAs生长层表面缺陷,衬底偏角生长温度及其它生长条件也进行了初步探讨。     

DETERMINATION OF CAPTURE BARRIERS OF DEFECTS FOR GaAs ALLOYS AND TRANSIENT PHOTO-RESISTIVITY SPECTROSCOPY

Si-doped Ga_0.7Al_0.3As grown by molecular beam epitaxy (MBE) and undoped Ga_0.47Al_0.53As grown by chemical beam epitaxy (CBE) have been investigated using a new deep level characterization method-transient photo-resistivity spectroscopy, which we recently developed. This method measures directly the capture process of deep centers. In GaAlAs, apparent capture barrier energy E_B= 0.25eV of DX center was determined and intrinasic capture barrier energy E_σ = 0.16eV was directly measured. In GaInAs, a defect with capture barier energy E_B= 0.2BeV was observed. The result proved that DX centers capture electron only from band L, belonging to small lattice relaxation model. The theoretical deduction of transient photo-resistivity spectroscopy was improved.     

富Sb状态下GaSb/AlGaSb异质结的液相外延生长

本文分析了以往在制作GaSb/Al_xGa_1-xSb结构雪崩光电二极管(APD)中存在的问题,提出了在富Sb状态下进行液相外延(LPE)生长GaSb/AlGaSb异质结APD的方法。经过多次试验获得了在富Sb状态下Al-Ga-Sb三元系相图数据,并且在富Sb状态下液相外延生长出了优良的AlGaSb外延层。     

Ⅰ类和Ⅱ类准周期半导体超晶格的电子子带和波函数

本文将包迹函数近似推广用于计算有理数近似下,垂直于超晶格轴的波矢K_⊥不等于零时,准周期半导体超晶格(QSS)的电子子带和波函数,对K_⊥=0的情形,分别计算了Ⅰ类的GaAs/Al_xGa_1-xAs和Ⅱ类的InAs/GaSb QSS的电子子带和波函数,直至代序数m=9和6。对于价带对导带影响强的InAs/GaSb QSS,分别计算了m=5和6时电子子带随K_⊥的变化关系。并提出了利用本文结果计算Ⅰ类的GaAs/Al_xGa_1-xAs QSS带间集体激发的具体方法。     

非对称方势阱中的激子及其与声子的相互作用

采用类LLP(Lee-Low-Pines)变换和分数维变分法,在讨论有限深非对称方势阱Ga_1－xAl_xAs/ GaAs/Ga_0.7Al_0.3As的分数维基础上,计算了其中激子的基态能量以及声子对其影响,随着势阱宽度增加,激子能量先减小后增大,出现一个最小值.讨论了一侧势垒高度变化对分数维、激子基态能量的影响,并发现声子作用使得激子能量明显增大.另外,非对称方势阱中的激子结合能随阱宽的减小而增     

MOCVD生长Ga0.5In0.5P外延层光学性质的研究

本文用光致发光(PL)研究了MOCVD(金属氧化物化学气相沉积)生长的有序Ga_0.5In_0.5P外延层的光学性质.发现有序程度较强的Ga_0.5In_0.5样品的PL谱中一峰的能量随温度升高,先增大而后又减小.根据已有的报道和本文的实验结果,提出了一个有序Ga_0.5In_0.5P的模型,模型中将有序Ga_0.5In_0.5P看作阶宽随机分布的Ⅱ型多量子阱结构,能带边之下存在带尾态,并用该模型对实验结果进行了较好的解释.     

He+辐照对Ga0.94Mn0.06As薄膜铁磁性的改善

离子辐照半导体可以很好的改善半导体材料的磁学性质.用He⁺ 辐照Ga_0.94Mn_0.06As薄膜,可以较方便的调制Ga_0.94Mn_0.06As 薄膜中产生铁磁性载体的浓度.由于空穴居间而导致Ga_0.94Mn_0.06As薄膜的铁磁性, 可以通过He⁺的辐照来得到改善,其结果是Ga_0.94Mn_0.06As薄膜的矫顽力可以增加3倍多. 当He⁺辐照流强增加时, 居里温度和沿着样品面外磁化难轴方向的饱和磁场都减小了. 被辐照的Ga_0.94Mn_0.06As薄膜的电学性质和结构特征显示, He⁺辐照Ga_0.94Mn_0.06As薄膜可以有控制地改善它的铁磁性, 其结果源于He⁺辐照Ga_0.94Mn_0.06As薄膜所诱导产生电缺陷对空穴的补偿, 而不是He⁺辐照改变了Ga_0.94Mn_0.06As薄膜的结构.     

InxGa1－xAs缓冲层上InyGa1－yAs/(Al)Ga

本文中,发现在In_xGa_1-xAs缓冲层上非故意掺杂的In_yGa_1-yAs/(Al)GaAs超晶格样品中存在着两个互相反向的自建电场区,一个位于样品表面,另一个位于In_xGa_1-xAs缓冲层和超晶格界面。据此,合理地解释了样品的光伏测试结果,并对此类样品的MOCVD生长工艺给予指导。     

1.55μm InGaAsP/InP应变量子阱激光器的LP－MOCVD生长

本文首次报导了生长温度为550℃,以三甲基镓(TMGa)和三甲基铟(TMIn)为Ⅲ族源,用低压金属有机物气相沉积(LFMOCVD〕技术,高质量1.62um和1.3umInGaAsP及In_0.57Ga_0.43As_0.98P_0.04/In_0.73Ga_0.27As_0.6P_0.4量子阶结构的生长,并给出了1.55umGaAsP/InP分别限制应变量子阱结构激光器的生长条件,激光器于室温下脉冲激射,其阈值电流密度为2.4kA/cm².     

GaInP材料生长及其性质研究

用常压MOCVD在半绝缘GaAs衬底上生长了Ga_xIn_1-xP(x=0.476～0.52)外延层,对外延层进行了X光双晶衍射、Hall和光致发光(PL)测试.77K下电子迁移率达3300cm²/V.s(浓度为1.4×10¹⁶cm^-3).载流子浓度随生长温度升高,随Ⅴ/Ⅲ比的增大而降低,并提出P空位(V_p)是自由载流子的一个重要来源,17KPL谱中,Ga_0.5In_0.5P(Tg=650℃,Ⅴ/Ⅲ=70)的峰能为1.828eV,半峰宽为19meV.另外,在1.849eV处还有一较弱的峰,GaInP峰能和其计算的带隙最大相差113meV,这可能与GaInP中杂质或缺陷以及其中存在有序结构有关.     

Influence of Ga(Al)As substrates on surface morphology and critical thickness of InGaAs quantum dots

Influence of Ga(Al)As substrates on surface morphology of InGaAs quantum dots and critical thickness of In_0.5Ga_0.5As film grown by molecular beam epitaxy is investigated. The In_0.5Ga_0.5As quantum dots are grown on (001) surfaces of GaAs and Al_0.25Ga_0.75 A at 450 °C, scanning tunneling microscope images show that the size of quantum dots varied slightly for 10 ML of In_0.5Ga_0.5As grown on GaAs and Al_0.25Ga_0.75As surfaces. Reflection high energy electron diffraction (RHEED) is used to monitor the growth of 4 monolayers (ML) In_0.5Ga_0.5As on Al_0.25Ga_0.75As and GaAs surfaces during deposition. The critical thickness is theoretically calculated by adding energy caused by surface roughness and heat from substrate. The calculations show that the critical thickness of In_0.5Ga_0.5As grown on GaAs and Al_0.25Ga_0.75As are 3.2 ML and 3.8 ML, respectively. The theoretical calculation agrees with the experimental results.     

Performance comparison of Pt/Au and Ni/Au Schottky contacts on AlxGa1-x N/GaN heterostructures at high temperatures

In contrast with Au/Ni/Al 0.25 Ga 0.75 N/GaN Schottky contacts,this paper systematically investigates the effect of thermal annealing of Au/Pt/Al 0.25 Ga 0.75 N/GaN structures on electrical properties of the two-dimensional electron gas in Al 0.25 Ga 0.75 N/GaN heterostructures by means of temperature-dependent Hall and temperature-dependent current-voltage measurements.The two-dimensional electron gas density of the samples with Pt cap layer increases after annealing in N 2 ambience at 600℃ while the annealing treatment has little effect on the two-dimensional electron gas mobility in comparison with the samples with Ni cap layer.The experimental results indicate that the Au/Pt/Al 0.25 Ga 0.75 N/GaN Schottky contacts reduce the reverse leakage current density at high annealing temperatures of 400-600℃.As a conclusion,the better thermal stability of the Au/Pt/Al 0.25 Ga 0.75 N/GaN Schottky contacts than the Au/Ni/Al 0.25 Ga 0.75 N/GaN Schottky contacts at high temperatures can be attributed to the inertness of the interface between Pt and AlxGa1-xN.     

稳定自然对流下的温度梯度液相外延

介绍了稳定自然对流下的温度梯度液相外延,稳定自然对流由加在溶液上的水平温差产生,用简化模式计算了该生长的生长速率,计算给出:该生长的生长速率与水平温差的平方根成比例;具体对Ga_0.85Al_0.15AS生长,在本工作给定的条件下,生长速率为稳态扩散理论预示生长速率的1124倍,在大部份生长面积内,外延层的厚度变化小于平均厚度的±10％,设计了稳定自然对流下的温度梯度液相外延装置,用该装置生长了厚Ga_1-xAl_xAs层,实 关键词：     

AlxGa1-xAs(100)表面性质的研究

用紫外光电子能谱研究了Al_0.7Ga_0.3As的表面态结构,观察到Al_0.7Ga_0.3As在价带中的两个表面态结构。在1500L原子氢吸附后消失。研究了这两个表面态结构在热退火消除表面损伤过程中的变化。结合LEED和XPS的实验结果,确定在450℃左右的热退火可以有效地消除损伤,获得一个完整的Al_0.7Ga_0.3As(100)表面。 关键词：     

Spacer layer thickness fluctuation scattering in a modulation-doped AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well

We theoretically study the influence of spacer layer thickness fluctuation（SLTF） on the mobility of a twodimensional electron gas（2DEG） in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer.     

Tunneling resonances in structures with a two-step barrier

Electron transport through an asymmetric heterostructure with a two-step barrier N⁺GaAs/N⁻GaAs/Al_0.4Ga_0.6As/Al_0.03Ga_0.97As/N⁻GaAs/N⁺GaAs was investigated. Features due to resonance tunneling both through a size-quantization level in a triangular quantum well, induced by an external electric field in the region of the bottom step of the barrier (Al_0.03Ga_0.97As layer), and through virtual levels in two quantum pseudowells of different width are observed in the tunneling current. The virtual levels form above the bottom step or above one of the spacers (N⁻GaAs layer) as a result of interference of electrons, in the first case on account of reflection from the Al_0.4Ga_0.6As barrier and a potential jump at the Al_0.03Ga_0.97As/N⁻GaAs interface and in the second case — from the Al_0.4Ga_0.6As barrier and the potential gradient at the N⁻GaAs/N⁺GaAs junction, reflection from which is likewise coherent. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 814–819 (25 May 1998)     

(Al0.1Ga0.9)0.5In0.5P材料的MOCVD生长温度窗口研究

用来制作光电子器件的(Al0.1Ga0.9)0.5 In0.5P为直接带隙的四元合金材料,对应的发光波长为630 nm,在其LP-MOCVD (low press-metalorganic chemical vapor deposition)外延生长过程中温度的高低成为影响其质量的关键,找到合适的生长温度窗口很有必要.实验中分别在700℃,680℃,670℃和660℃的条件下生长出作为发光二极管有源区的(Al0.1Ga0.9)0.5 In0.5P多量子阱结构,通过PL谱的测试对比分析,找出最佳生长温度在670℃附近.之后对比各外延片的PL谱、表面形貌,并对反应室的气流场进行了模拟,对各温度下生长状况的原因作出了深入分析.分析得到,高温下In组分的再蒸发会引起晶格失配并导致位错;低温下O杂质的并入会形成大量非辐射复合中心影响晶体质量,因此导致了(Al0.1Ga0.9)0.5In0.5P生长温度窗口较窄,文章最后提出In源有效浓度的提高是解决高温生长的一条有效途径.     

Microstructural and optical properties of strain compensated InxGa1−xAs/InyAl1−yAs multiple quantum wells

Transmission electron microscopy (TEM) and photocurrent (PC) measurements were carried out to investigate the microstructural and excitonic transitions in In_0.52Ga_0.48As/In_0.55Al_0.45As multiple quantum wells (MQWs). TEM images showed that high-quality 11-period strain-compensated In_0.52Ga_0.48As/In_0.55Al_0.45As MQWs had high-quality heterointerfaces. Based on the TEM results, a possible crystal structure for the In_0.52Ga_0.48As/In_0.55Al_0.45As MQWs is presented, and their strains are compensated. The results for the PC data at 300 K for several applied electric fields showed that several excitonic transitions shifted to longer wavelengths as the applied electric field increased. These results indicate that the strain-compensated In_0.52Ga_0.48As/In_0.55Al_0.45As MQWs hold promise for electroabsorption modulator devices.     

用肖特基电容电压特性数值模拟法确定调制掺杂AlxGa1-xN/GaN异质结中的极化电荷

研究发展了用肖特基电容电压特性数值模拟确定调制掺杂Al_xGa_1-xN/GaN异质结中极化电荷的方法.在调制掺杂的Al_0.22Ga_0.78N/GaN异质结上制备了Pt肖特基接触,并对其进行了C-V测量.采用三维费米模型对调制掺杂的Al_0.22Ga_0.78N/GaN异质结上肖特基接触的C-V特性进行了数值模拟,分析了改变样品参数对C-V特性的影响.利用改变极化电荷、n-AlGaN 关键词： xGa_1-xN/GaN异质结')" href="#">Al_xGa_1-xN/GaN异质结 极化电荷 电容电压特性 数值模拟