Pendeo-Epitaxy - A New Approach for Lateral Growth of Gallium Nitride Structures
Pendeo-Epitaxy - A New Approach for Lateral Growth of Gallium Nitride Structures
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Pendeo-Epitaxy - 氮化镓结构横向生长的新方法
DOI：
10.1557/proc-537-g3.38
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
R. Davis
中科院分区：
文献类型：
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作者：
T. Zheleva;Scott A. Smith;D. Thomson;T. Gehrke;K. Linthicum;P. Rajagopal;E. Carlson;W. M. Ashmawi;R. Davis
讨论了一种新的横向生长近无缺陷GaN结构的工艺路线。通过MOVPE技术实现了从[0001]取向的GaN柱的{11 2 0}侧壁悬置的GaN膜到相邻的蚀刻威尔斯中和上方的横向生长，而不使用或接触支撑掩模或衬底。悬垂外延被提议作为这种生长技术的描述性术语。使用促进GaN的{ 11 2 0）平面的横向生长并且不允许该相在暴露的SiC衬底上成核的工艺参数来实现选择性生长。因此，选择性是通过调整下面的GaN层本身的形状来提供的，该GaN层本身由一系列交替的沟槽和柱组成，而不是像传统的横向外延过生长（LEO）那样通过SiO2或SiN x掩模中的开口进行选择性生长。通过MOVPE观察到两种悬垂外延GaN生长的引发模式：模式A -促进{11 2 0}侧面进入威尔斯的横向生长快于（0001）顶面的垂直生长;以及模式B -使得顶面（0001）能够初始更快地生长，随后在威尔斯上从新形成的{1120}侧面。通过透射电子显微镜（TEM）观察到悬垂外延GaN中的位错密度相对于GaN柱中的位错密度降低了四到五个数量级。TEM观察表明，在悬垂外延GaN膜中，当结构从侧壁横向生长到沟槽中和沟槽上方时，位错不会从GaN柱横向传播。扫描电子显微镜（SEM）的研究表明，合并的区域要么是无缺陷的，有时表现出空隙。在这些空隙之上，PEGaN层通常是无缺陷的。
A new process route for lateral growth of nearly defect free GaN structures via Pendeoepitaxy is discussed. Lateral growth of GaN films suspended from {11 2 0} side walls of [0001] oriented GaN columns into and over adjacent etched wells has been achieved via MOVPE technique without the use of, or contact with, a supporting mask or substrate. Pendeo-epitaxy is proposed as the descriptive term for this growth technique. Selective growth was achieved using process parameters that promote lateral growth of the { 11 2 0) planes of GaN and disallow nucleation of this phase on the exposed SiC substrate. Thus, the selectivity is provided by tailoring the shape of the underlying GaN layer itself consisting of a sequence of alternating trenches and columns, instead of selective growth through openings in SiO 2 or SiN x mask, as in the conventional lateral epitaxial overgrowth (LEO). Two modes of initiation of the pendeo-epitaxial GaN growth via MOVPE were observed: Mode A - promoting the lateral growth of the {11 2 0} side facets into the wells faster than the vertical growth of the (0001) top facets; and Mode B - enabling the top (0001) faces to grow initially faster followed by the pendeo-epitaxial growth over the wells from the newly formed {11 2 0} side facets. Four-to-five order decrease in the dislocation density was observed via transmission electron microscopy (TEM) in the pendeo-epitaxial GaN relative to that in the GaN columns. TEM observations revealed that in pendeo-epitaxial GaN films the dislocations do not propagate laterally from the GaN columns when the structure grows laterally from the sidewalls into and over the trenches. Scanning electron microscopy (SEM) studies revealed that the coalesced regions are either defect-free or sometimes exhibit voids. Above these voids the PEGaN layer is usually defect free.