ELECTRO-LUMINESCENCE AND PHOTO-LUMINESCENCE FROM STRAINED SiGe/Si QUANTUM WELL

Photo-luminescence and electro-luminescence from step-graded index SiGe/Si quantum well grown by molecular beam epitaxy is reported. The SiGe/Si step-graded index quantum well structure is beneficial to the enhancing of electro-luminescence. The optical and electrical properties of this structure are discussed.     

AlyGa1-yAs/AlxGa1-xAs量子阱激光器材料的光致荧光谱

测量了Al_yGa_1-yAs/Al_xGa_1-xAs量子阱激光材料的光致荧光谱.发现在室温连续激光器材料的光致荧光谱中有两个峰,而不能激射的材料中则只有一个很宽的峰.将高能峰归属于准费密能级电子的跃迁. 关键词：     

阶梯量子阱子带跃迁二次谐波产生的研究

本文理论上利用二能级近似下的传递矩阵法,给出了GaAs/Al_xGa_1-xAs二阶非线性光学系数X_2ω⁽²⁾的解析表达式,通过数值计算,设计了具有较大X_2ω⁽²⁾的阶梯多量子阱(SMQW)结构,其特点是单共振泵浦,实验上验证了该结构确实具有比体材料大3个量级的X_2ω⁽²⁾值,为了提高二次谐波(SHG)的转换效率,我们分别设计了两种新型的实验方案,分别使SHG转换效率较Brewster角入射下大10倍和100倍。     

InAlAs/InGaAs/InP异质结构的X射线双晶衍射研究

本文应用X射线双晶衍射技术结合X射线衍射动力学理论的计算模拟,研究了MBE生长的InGaAs/InAlAs/InP异质结结构材料的外延层生长条件与层厚、成分的关系,X射线双晶衍射形貌图表明:衬底和外延膜存在位错和沉淀物等缺陷,衬底的不完美性直接影响外延膜的质量,文中还应用X射线衍射动力学理论对所观察到的沉淀物衬度进行解释,指出沉淀物周围点阵受张应变场。     

Direct observation of the carrier transport process in InGaN quantum wells with a pn-junction

A new mechanism of light-to-electricity conversion that uses InGaN/GaN QWs with a p-n junction is reported.According to the well established light-to-electricity conversion theory,quantum wells(QWs) cannot be used in solar cells and photodetectors because the photogenerated carriers in QWs usually relax to ground energy levels,owing to quantum confinement,and cannot form a photocurrent.We observe directly that more than 95% of the photoexcited carriers escape from InGaN/GaN QWs to generate a photocurrent,indicating that the thermionic emission and tunneling processes proposed previously cannot explain carriers escaping from QWs.We show that photoexcited carriers can escape directly from the QWs when the device is under working conditions.Our finding challenges the current theory and demonstrates a new prospect for developing highly efficient solar cells and photodetectors.     

InGaAs/InAlAs多量子阱结构的量子限制Stark效应研究

通过吸收光电流谱的测量.观察到用国产MBE设备生长的与InP衬底晶格匹配的In-GaAs/InAlAs多量子阱结构的量子限制Stark效应及其与光偏振方向有关的各向异性电吸收特性.报道了可用于波导型调制器制作的MQW样品材料的X射线双晶衍射结果,并用计算机模拟出与实测十分相似的曲线,得到了可靠的量子阱结构参数,证明样品材料具有优良的外延质量.利用等效无限深阱模型进行的理论计算表明,应考虑样品p-i-n结内建电场的影响,才能使算出的吸收边红移与实验值符合. 关键词：