垂直堆垛InAs量子点材料的分子束外延生长

用MBF设备以Stranski-Krastanov生长方式外延生长了5个周期垂直堆垛的InAs量子点，在生长过程中使用对形状尺寸控制法来提高垂直堆垛InAs量子点质量和均匀性。样品外延的主要结构是500nm的GaAs外延层，15nm的Al0．5Ga0．5As势垒外延层，5个周期堆跺的InAs量子点，50nm的Al0．5Ga0．5Asnm势垒外延层等。在生长过程中用反射式高能电子衍射仪(RHEED)实时监控。生长后用原子力显微镜(AFM)进行表面形貌的表征，再利用光制发光(PL)对InAs量子点进行观测。     

分子束外延InAs量子点材料的透射电子显微镜研究

报道了利用分子束外延技术在(001)GaAs衬底上生长的单层及多层InAs量子点材料的透射电子显微镜(TEM)研究结果,并对量子点的结构特性进行了讨论.结果表明:多层量子点呈现明显的垂直成串排列趋势;随着InAs量子点层数的增加,量子点的密度下降,其尺寸随层数的增加趋向均匀.在试验条件下,5层量子点材料的InAs量子点厚度和GaAs隔离层的厚度的选择都比较合理,其生长过程中的应变场更有利于自组织量子的形成.     

Growth of GaN/AlxGa1-xN (x=0.65) Superlattices on Si(111) Substrates Using RF-MBE

Superlattices with varying GaN well widths (2, 3, 6, 9 nm) and fixed AlGaN barrier (8 nm) with high Al-content (x=0.65) were grown. Streaky RHEED patterns indicated 2D growth mode for the superlattices. XRD measurements showed multiple satellite peaks corresponding to uniform periodicity of the GaN/AlGaN pairs. The AlGaN barrier XRD peak also shifted with increasing well widths, while the GaN XRD peak was nominally unchanged. Room temperature photoluminescence experiments revealed peak emissions at energies lower than the bulk GaN energy gap. The large red shift with respect to the bulk gap is attributed to significant Stark effect for wide multiple quantum wells.