生长温度对In0.53Ga0.47As/InP的LPMOCVD生长影响

利用LPMOCVD技术在InP衬底生长了InxGa1-xAs材料，获得表面平整．光亮的In0.53Ga0.47As外延层。研究了生长温度对InxGa1-xAs外延层组分、表面形貌、结晶质量、电学性质的影响。随着生长温度的升高，为了保证铟在固相中组分不变，必须增加三甲基铟在气相中的比例。在生长温度较高时，外延层表面粗糙。生长温度在630℃与650℃之间，X射线双晶衍射曲线半高宽最窄，高于或低于这个温度区间，半高宽变宽。迁移率随着生长温度的升高而增加,在630℃为最大值，然后随着生长湿度的升高反而降低。生长温度降低使载流子浓度增大，在生长温度大于630℃时载流子浓度变化较小。     

缓冲层生长温度对In0.82Ga0.18As 薄膜结构及电学性能的影响

采用低压金属有机化学气相沉积(LP-MOCVD)技术,两步生长法在InP衬底上制备In_0.82Ga_0.18As材料。研究缓冲层的生长温度对In_0.82Ga_0.18As薄膜的结构及电学性能的影响。固定外延薄膜的生长条件,仅改变缓冲层生长温度(分别为410,430,450,470 ℃),且维持缓冲层其他生长条件不变。用拉曼散射研究样品的结构性能,测量四个样品的拉曼散射光谱,得到样品的GaAs的纵向光学(LO)声子散射峰的非对称比分别为1.53,1.52,1.39和1.76。测量样品的霍耳效应表明,载流子浓度随缓冲层生长温度变化而改变,同时迁移率也随缓冲层生长温度变化而改变。通过实验得出:缓冲层的生长温度能够影响In_0.82Ga_0.18As薄膜的结构及电学性能。最佳的缓冲层生长温度为450 ℃。     

In_(0.82)Ga_(0.18)As材料的低温电学性质研究

利用低压-金属有机化学气相沉积(LP-MOCVD)设备,采用两步生长及缓冲层热退火处理在InP衬底上制备了高质量的In0.82Ga0.18As外延材料.研究了缓冲层退火前后In0.82Ga0.18As外延材料的低温电学性质,通过变温霍尔效应测试得到了载流子的浓度和迁移率随温度变化的关系,并利用位错散射、极化光学声子散射等对实验数据进行了拟合.结果表明,实验值与理论值符合较好,在较低温度下(150K),位错散射起主要作用,而在较高的温度下(250K),极化光学声子散射占主要地位.     

基于silvaco-TCAD的In0.53Ga0.47As/InP红外探测器的仿真

采用silvaco-TCAD研究In0.53Ga0.47As/InP SAGCM-APD光电探测器,对探测器的结构参数对器件的电场分布、击穿电压和贯穿电压的影响进行仿真分析。研究表明电荷层对器件内部电场起到更好的调节作用,但过高的电荷层面密度会导致APD探测器的击穿电压与贯穿电压之差减小。倍增层厚度的增加使击穿电压先减小后增高,贯穿电压线性增加,同时耗尽层宽度变大,使器件电容减小。当倍增区厚度1 μm、偏压为-5 V时,器件电容密度达到了4.5×10-17 F/μm。反向偏置电压为30 V时,APD探测器在1.31 μm和1.55 μm波长下的响应度分别达到1 A/W和1.1 A/W     

应力导致InAs/In0.15Ga0.85As量子点结构中 In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术,在In0.15Ga0.85As/GaAs量子阱生长了两个InAs/In0.15Ga0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In0.15Ga0.85As阱层的厚度和生长温度,获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果,发现该样品量子点的光学性质也同时得到了极大的优化.基于有效质量近似的数值计算结果表明:量子点后生长过程中应力导致In0.15Ga0.85As阱层合金分解机理是导致量子点尺寸和光学性质得到优化的主要原因.     

MOCVD生长Si衬底上HT-AlN缓冲层低生长压力对GaN薄膜的影响

采用金属有机化学气相沉积（MOCVD）技术在Si（111）衬底上外延GaN薄膜,对高温AlN（HT-AlN）缓冲层在小范围内低生长压力（6.7~16.6 kPa）条件下对GaN薄膜特性的影响进行了研究。研究结果表明GaN外延层的表面形貌、结构和光学性质对HT-AlN缓冲层的生长压力有很强的的依赖关系。增加HT-AlN缓冲层的生长压力,GaN薄膜的光学和形貌特性均有明显改善,当HT-AlN缓冲层的生长压力为13.3 kPa时,得到无裂纹的GaN薄膜,其（002）和（102）面的X射线衍射峰值半高宽分别为735 arcsec和778 arcsec,由拉曼光谱计算得到的张应力为0.437 GPa,原子力显微镜（AFM）观测到表面粗糙度为1.57 nm。     

磁控反应溅射AlN缓冲层对GaN基LED器件性能的影响

以直流磁控反应溅射法(RMS)在图形化蓝宝石衬底上制备的AlN薄膜作为缓冲层,采用金属有机化学气相沉积法(MOCVD)外延生长了GaN基LED。与MOCVD生长的低温GaN缓冲层相比,RMS制备的AlN缓冲层具有表面更平整、颗粒更小的形核岛,有利于促进GaN外延的横向生长,减少了形核岛合并时的界面数量和高度差异,降低了缺陷和位错产生的几率。研究结果表明,溅射AlN缓冲层取代传统低温GaN缓冲层后,外延生长的GaN材料具有更高的晶体质量,LED器件在亮度、漏电和抗静电能力等光电特性上均有明显提升。     

缓冲层InxGa1-xAs组分对In0.82Ga0.18As结晶质量和表面形貌的影响

采用低压金属有机化学气相沉积(LP-MOCVD)技术,两步生长法在InP衬底上制备In_0.82Ga_0.18As材料.研究缓冲层In_xGa_1-xAs的In组分对In_0.82Ga_0.18As结晶质量和表面形貌的影响.X射线衍射(XRD)用于表征材料的组分和结晶质量.用扫描电子显微镜(SEM)观察样品的表面形貌.实验结果表明,低温生长的缓冲层In_xGa_1-xAs的In组分影响高温生长的外延层In_0.82Ga_0.18As的结晶质量和表面形貌.测量得到四个样品的外延层In_0.82Ga_0.18As的X射线衍射谱峰半峰全宽(FWHM)为0.596°,0.68°,0.362°和0.391°,分别对应缓冲层In组分x=0.28,0.53,0.82,0.88,当缓冲层In组分是0.82时,FWHM最窄,表明样品的结晶质量最好.SEM观察四个样品的表面形貌,当缓冲层In组分是0.82时,样品的表面平整,没有出现交叉平行线或蚀坑等缺陷,表面形貌最佳.     

H2载气流量对AlN缓冲层生长的影响

在Si(111)衬底上用金属有机化学气相沉积(MOCVD)设备生长了AlN和GaN薄膜。采用高分辨X射线衍射、椭圆偏振光谱仪和原子力显微镜研究了AlN缓冲层生长时的载气(H2)流量变化对GaN外延层的影响。椭圆偏振仪测试表明:相同生长时间内AlN的厚度随着H2流量的增加而增加,即H2流量增加会导致AlN生长速率的提高。原子力显微镜测试表明:随着H2流量的增加,AlN表面粗糙度也呈上升趋势。XRD测试表明:随着AlN生长时的H2流量的增加,GaN的(0002)和(1012)峰值半宽增大,即螺型穿透位错密度和刃型穿透位错密度增加。可能是由于AlN缓冲层的表面形貌较差,导致GaN的晶体质量有所下降。实验结果表明:采用较低的H2流量生长AlN缓冲层可以控制AlN的生长速率,在一定程度上有助于提高GaN的晶体质量。     

In0.53Ga0.47As/InP量子阱与体材料的1 MeV电子束辐照光致发光谱研究

为获得对In_0.53Ga_0.47As/InP材料在电子束辐照下的光致发光谱变化规律, 开展了1 MeV电子束辐照试验, 注量为 5×10¹²-9×10¹⁴ cm^-2. 样品选取量子阱材料和体材料, 在辐照前后, 进行了光致发光谱测试, 得到了不同结构In_0.53Ga_0.47As/InP材料在1 MeV电子束辐照下的不同变化规律; 对比分析了参数退化的物理机理. 结果显示: 试验样品的光致发光峰强度随着辐照剂量增大而显著退化. 体材料最先出现快速退化, 而五层量子阱在注量达到6×10¹⁴ cm^-2时, 就已经退化至辐照前的9%. 经分析认为原因有: 1)电子束进入样品后, 与材料晶格发生能量传递, 破坏晶格完整性, 致使产生的激子数量减少, 光致发光强度降低; 电子束辐照在材料中引入缺陷, 增加了非辐射复合中心密度, 导致载流子迁移率降低. 2)量子阱的二维限制作用使载流子运动受限, 从而能够降低载流子与非辐射复合中心的复合概率; 敏感区域截面积相同条件下, 体材料比量子阱材料辐射损伤更为严重. 3)量子阱的层数越多, 则异质结界面数越多, 相应的产生的界面缺陷数量也随之增多, 辐射损伤越严重.     

Control of symmetric properties of metamorphic In_(0.27)Ga_(0.73)As layers by substrate misorientation

Asymmetry in dislocation density and strain relaxation has a significant impact on device performance since it leads to anisotropic electron transport in metamorphic materials. So it is preferred to obtain metamorphic materials with symmetric properties. In this paper, we grew metamorphic In_(0.27)Ga_(0.73) As epilayers with symmetric low threading dislocation density and symmetric strain relaxation in two (110) directions using In Al Ga As buffer layers on 7°misoriented Ga As(001)substrates. To understand the control mechanism of symmetric properties of In_(0.27)Ga_(0.73) As layers by the substrate miscut angles, In_(0.27)Ga_(0.73) As grown on 2°and 15°misoriented substrates were also characterized as reference by atomic force microscopy, transmission electron microscopy, and high resolution triple axis x-ray diffraction. The phase separation and interaction of 60°misfit dislocations were found to be the reasons for asymmetry properties of In_(0.27)Ga_90.73 As grown on 2and 15°substrates, respectively. Photoluminescence results proved that the In_(0.27)Ga_(0.73) As with symmetric properties has better optical properties than the In_(0.27)Ga_(0.73) As with asymmetric properties at room temperature. These results imply that high quality metamorphic In_(0.27)Ga_(0.73) As can be achieved with controllable isotropic electron transport property.     

Influence of thermal annealing duration of buffer layer on the crystalline quality of In0.82Ga0.18As grown on InP substrate by LP-MOCVD

In_0.82Ga_0.18As epilayers were grown on InP substrates using a two-step growth technique by LP-MOCVD. A homogeneous low-temperature (450 °C) In_0.82Ga_0.18As buffer layer was introduced to improve the crystalline quality of epilayers. The influence of low-temperature buffer layer deposition condition, such as thermal annealing duration, on the crystalline quality of the In_0.82Ga_0.18As epilayer was investigated. Double-crystal X-ray diffraction measurement, Hall measurement, and Raman scattering spectrum were used to evaluate the In_0.82Ga_0.18As epilayers. Atomic force microscope was used to study the surface morphology. It is found that the In_0.82Ga_0.18As epilayer, with buffer layer thermal annealing for 5 min, exhibits the best crystalline quality. The change of the surface morphology of the buffer layer after thermal annealing treatment was suggested to explain the phenomenon.     

Spectral response modeling and analysis of p-n-p In_(0.53)Ga_(0.47)As/InP HPTs

We report our results on the modeling of the spectral response of the near-infrared(NIR) lattice-matched p-n-p In_(0.53)Ga_(0.47)As/InP heterojunction pbototransistors(HPTs).The spectral response model is developed from the solution of the steady state continuity equations that dominate the excess optically generated minority-carriers in the active regions of the HPTs with accurate boundary-conditions.In addition,a detailed optical-power absorption profile is constructed for the device modeling.The calculated responsivity is in good agreement with the measured one for the incident radiation at980 nm,1310 nm,and 1550 nm.Furthermore,the variation in the responsivity of the device with the base region width is analyzed.     

Determination of breakdown voltage of In_(0.53)Ga_(0.47)As/InP single photon avalanche diodes

We examine the saturation of relative current gain of In0.53 Ga0.47As/InP single photon avalanche diodes(SPADs) operated in Geiger mode.The punch-through voltage and breakdown voltage of the SPADs can be measured using a simple and accurate method.The analysis method is temperature-independent and can be applied to most SPADs.     

AlN缓冲层对Si基GaN外延薄膜性质的影响

采用金属有机化合物化学气相沉积（MOCVD）方法制备了不同AlN缓冲层厚度的GaN样品,研究了AlN缓冲层厚度对GaN外延层的应力、表面形貌和晶体质量的影响。研究结果表明：厚度为15 nm的AlN缓冲层不仅可以有效抑制Si扩散,而且还给GaN外延层提供了一个较大的压应力,避免GaN薄膜出现裂纹。在该厚度AlN缓冲层上制备的GaN薄膜表面光亮、无裂纹,受到的张应力为0.3 GPa,（0002）和（1012）面的高分辨X射线衍射摇摆曲线峰值半高宽分别为536 arcsec和594 arcsec,原子力显微镜测试得到表面粗糙度为0.2 nm。     

温度对Al_(0.5)Ga_(0.5)As/AlAs分布布喇格反射器的反射谱影响

采用光学传输矩阵理论对Al0.5Ga0.5As/AlAs材料分布布喇格反射器(DBR)进行理论研究,分析了-10℃到100℃的范围内,温度变化对不同DBR结构的反射光谱影响.结果表明:随着温度的升高,传统20周期DBR的反射光谱向长波长方向移动,速率约0.05 nm/℃,其中由线热膨胀系数带来的影响小于0.001 nm/℃.当传统DBR的周期数增大时,温度对DBR光谱反射率的影响在减小,同时DBR的反射谱峰值波长发生红移.为了降低温度对DBR反射光谱的影响,提出一种新型的复式DBR结构.分析指出:该复式DBR比传统DBR有更大的反射光谱半峰宽,基本能覆盖同温度的AlGaInP LED电致发光光谱,这对提高LED的出光效率有现实意义.     

Lasing and spontaneous emission characteristics of 1.3 μm In(Ga)As quantum-dot lasers

We demonstrate that excellent 1.3 μm QD laser performance can be achieved with the use of a high-temperature step during the growth of the GaAs spacer layers. An optimised laser structure exhibits a very low room-temperature J_th and operates CW from the ground-state up to at least 105 °C. Spontaneous emission measurements indicate that the high-temperature performance is limited by non-radiative processes rather than by the thermal excitation of carriers into higher energy QD states.