InGaN量子点的诱导生长和发光特性研究

Induced Growth and Optical Property Study of InGaN Quantum Dots

降低InGaN的维数是提高GaN基发光器件发光效率的一种非常有效的方法,本文的工作主要集中在高密度InGaN量子点的生长和分析上。在MOCVD设备上,经过钝化和低温两个特殊工艺条件,在高温GaN表面生长了一层低温岛状GaN,形成表面形貌的起伏,进而导致表面应力的不均匀分布。在这一层低温岛状GaN的诱导性作用下生长并形成InGaN量子点。通过原子力显微镜、透射电子显微镜和光致发光谱对其微观形貌和光学性质进行了观察和研究。从原子力显微镜以及透射电子显微镜观察得到的结果表明:InGaN量子点为平均直径约30nm、高度约25nm、分布较均匀的圆锥,其密度约1011cm-2。室温下,InGaN量子点材料的PL谱强度大大超出相同条件生长的InGaN薄膜材料。这些现象表明,用InGaN量子点代替普通InGaN薄膜,有望获得发光效率更高的GaN基发光器件。

Reducing InGaN dimensions is a effective way to increase the workefficiency of GaNbased light emitting devices (LED). This paper describes our research on the growths of InGaN quantum dots (QDs) and on the analyses of their properties. Instead of the usual StranskiKrastannow growth or surfactant induction, our method consists of three steps: an introduction of second buffer layer on a GaN/Al2O3 substrate, a passivation process for the buffer layer surface at a low temperature, a InGaN QDs fabrication by metal organic chemical vapor deposition (MOCVD). Based on our method, InGaN QDs with high density could be achieved, shown in this paper, we contribute these QDs formation to nonuniform surfacestress at the buffer layer surface. These InGaN QDs have been studied by atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL) techniques for their microstructure and optical properties respectively. It is shown that InGaN QDs distributed with the density of 1011cm-2 and appeared as cones with about 30nm diameter and 25nm height. The intensity of PL spectrum of InGaN QDs at room temperature is much higher than that of the normal InGaN film grown with the same growth condition, which may be used for making GaN based light emitting devices with high efficiency.