立方相GaN的持续光电导

研究了金属有机物化学气相外延 (MOVPE)方法生长的非故意掺杂的立方相 Ga N的持续光电导效应 .在六方相 Ga N中普遍认为持续光电导效应与黄光发射有关 ,而实验则显示在立方 Ga N中 ,持续光电导效应与其中的六方相 Ga N夹杂有关系 ,而与黄光发射没有关系 .文中提出 ,立方相 Ga N与其中的六方相 Ga N夹杂之间的势垒引起的空间载流子分离是导致持续光电导现象的物理原因 .通过建立势垒限制复合模型 ,解释了立方相 Ga N的持续光电导现象的物理过程 ,并对光电导衰减过程的动力学作了分析 .对实验数据拟合的结果证明以上的模型和推导是与实验相符的 .     

Thermodynamics and kinetics analysis of in-situ synthesizing AlN

AlN powders were prepared by in-situ synthesis technique. It is a reaction of binary molten Al-Mg alloys with highly pure nitrogen. It was confirmed through thermodynamics calculation that Mg element in Al-Mg alloys can decrease oxygen content in the reacting system. Thus, nitridation reaction can be performed to form AlN. Moreover, an analysis of kinetics shows that the nitridation reaction of Al-Mg alloys can be accelerated and transferred rapidly with the increment of Mg content.     

Lanxide技术合成含烧结助剂的复合AlN粉体

高纯度的氮气中,以Al-Mg-Y合金为母合金,利用Lanxide技术合成了含烧结助剂Y2O3的复合AlN粉体.通过扫描电镜、X射线衍射、粒径分析及化学成分分析等检测手段对氮化产物进行表征.实验结果表明,合金氮化反应完全,氮化产物疏松易于粉化.粉化后获得的复合AlN粉体具有纯度高,氧杂质含量低,粒度细小等优点.     

横向外延GaN结晶质量的同步辐射研究

采用同步辐射X光衍射技术研究了α-Al2O3(0001）衬底上横向外延GaN的结构特征。发现横向生长区的GaN（0001）晶面与窗口区的GaN(0001)晶面在垂直掩模方向上存在取向差。ω/2θ联动扫描发现横向生长区的GaN的衍射峰半高宽约为窗口区GaN的一半，这表明横向外延生长技术在降低GaN穿透位错密度的同时，还能大幅度提高GaN的晶粒尺寸。     

使用 X射线衍射技术判定 Si C单晶体的结构和极性

使用四圆衍射仪和双晶衍射技术 ,分析了 Si C体单晶的结构和极性 .Si C单晶体由化学气相淀积法获得 .六方 { 10 15 }极图证明了该单晶结构为 6 H型 .三轴晶衍射中的ω模式衍射强度的差异判定了该单晶的 Si终端面和 C终端面 ,即极性面。两个面的一、二、三级衍射强度的测量比值与经过散射因子修正后计算的结构振幅平方比值| F ( 0 0 0 L ) | 2 / | F( 0 0 0 L ) | 2 非常吻合 .因此 ,利用极性面的衍射强度差异 ,可以方便、严格地判断具有类似结构如 2 H{ 0 0 0 1}、4H { 0 0 0 1}及 3C- Si C{ 111}的极性     

使用X射线衍射技术判定SiC单晶体的结构和极性

使用四圆衍射仪和双晶衍射技术,分析了SiC体单晶的结构和极性．SiC单晶体由化学气相淀积法获得．六方｛1015｝极图证明了该单晶结构为6H型．三轴晶衍射中的ω模式衍射强度的差异判定了该单晶的Si终端面和C终端面,即极性面。两个面的一、二、三级衍射强度的测量比值与经过散射因子修正后计算的结构振幅平方比值｜F（000L）｜２／｜F（000L）｜２非常吻合．因此,利用极性面的衍射强度差异,可以方便、严格地判断具有类似结构如2H｛0001｝、4H｛0001｝及3C-SiC｛111｝的极性．     

Lanxide技术合成含烧结助剂的复合AIN粉体

高纯度的氮气中,以Al-Mg-Y合金为母合金,利用Lanxide技术合成了含烧结助剂Y_2O_3的复合AIN粉体.通过扫描电镜、X射线衍射、粒径分析及化学成分分析等检测手段对氮化产物进行表征.实验结果表明,合金氮化反应完全,氮化产物疏松易于粉化.粉化后获得的复合AIN粉体具有纯度高,氧杂质含量低,粒度细小等优点.     

Designing of 1 eV GaNAs/GaInAs superlattice subcell in current-matched four-junction solar cell

A reasonably-thick GaNAs/GaInAs superlattice could be an option as a roughly 1 eV subcell to achieve high-efficiency multi-junction solar cells on a lattice-matched Ge substrate. A detailed consideration of a high-efficiency design for a GaInP/GaAs/1 eV/Ge device is presented. Calculations have been done for this structure to obtain the confined energies of the electrons and holes by utilizing the Kronig-Penney model, as well as the absorption coefficient and thereby the external quantum efficiency. The effect of well layers, GaNAs or GaInAs, on the absorption and photocurrent density under the AM 1.5 condition is discussed in order to realize a requirement of current matching in the four-junction solar cells. The management of these considerations implies the feasibility of the GaNAs/GaInAs superlattice subcell design to improve the overall conversion efficiency of lattice matched GaInP/GaAs/1 eV/Ge cells.     

GaAs衬底上等离子体增强原子层沉积GaN薄膜

采用等离子体增强原子层沉积(PEALD)技术在斜切的砷化镓(GaAs)衬底上低温沉积了氮化镓(GaN)薄膜,对生长过程、表面机制以及界面特性等进行分析,得到GaN在215～270℃的温度窗口内生长速度(Growth-Per-Cycle, GPC)为0.082 nm/cycle,并从表面反应动力学和热力学方面对GPC的变化进行了分析。研究发现,生长的GaN薄膜为多晶,具有六方纤锌矿结构,且出现(103)结晶取向。在GaN/GaAs界面处观察到约1 nm厚的非晶层,这可能与生长前衬底表面活性位点的限制和前驱体的空间位阻效应有关。值得注意的是,在沉积的GaN薄膜中,所有的N皆与Ga以Ga-N键结合生成GaN,但是存在少部分Ga形成了Ga-O键和Ga-Ga键。这种成键方式,可能与GaN薄膜中存在的缺陷和杂质有关。     

Effects of growth temperature on high-quality In0.2Ga0.8N layers by plasma-assisted molecular beam epitaxy

High-quality In_0.2Ga_0.8N epilayers were grown on a GaN template at temperatures of 520 and 580℃ via plasma-assisted molecular beam epitaxy. The X-ray rocking curve full widths at half maximum (FWHM) of (10.2) reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature. When the growth temperature increases to 580℃, the FWHM of (00.2) reflections for these samples is very narrow and keeps similar, while significant improvement of (10.2) reflections with an FWHM value of 612 arcsec has been observed. This improved quality in InGaN layers grown at 580℃ is also reflected by the much larger size of the crystalline column from the AFM results, stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.