Formation of Photonic Crystals by Selective Area Growth and Their Applications

我们已经开发了一种技术，以形成二维周期性阵列的六边形柱和空气孔结构的二维晶体（2DPC）的应用选择性区域金属有机气相外延（SA-MOVPE）生长。首先在部分覆盖SiO_2掩模的（111）B GaAs衬底上进行GaAs和AlGaAs的SA-MOVPE。掩模图案的圆形或六边形开口阵列被布置以实现周期性约为0.5μm的三角形晶格。通过优化生长条件，在掩模衬底上成功地生长出了由垂直{110}面组成的均匀六方柱阵列结构，可用作2DPC。在（111）B InP掩模衬底上也生长了类似的六边形InGaAs柱阵列，并且发现其表现出适合于使用InP基材料的2DPC的高光学质量。此外，通过生长具有六边形SiO_2掩模的三角形晶格掩模衬底，我们成功地生长了具有六边形空气孔阵列的GaAs 2DPC结构，并优化了生长条件以抑制横向过生长。此外，通过在AlGaAs（111）B表面生长空气孔型2DPC，并对AlGaAs进行选择性底切刻蚀，也成功地制备出了2DPC平板。最后，利用平面波展开法计算了由六边形空气孔阵列和六边形介质棒组成的二维光子晶体的光子带隙，并与传统的圆形空气孔和圆形介质棒组成的二维光子晶体的光子带隙进行了比较。虽然光子带隙的整体特征非常相似，但空气孔和棒的形状存在差异，特别是在正三角形晶格中的六边形空气孔阵列中，TM和TE带隙的重叠增强，这对实现二维全光子带隙是有效的。

We have developed a technique to form two-dimensional periodic array of hexagonal pillars and air-hole structures for the application of two-dimensional crystals (2DPCs) by selective area metalorganic vapor phase epitaxial (SA-MOVPE) growth. Firstly, SA-MOVPE of GaAs and AlGaAs was carried out on (111)B GaAs substrates partially covered with SiO_2 masks. Array of circular or hexagonal openings of the mask pattern was arranged to realize triangular lattice with periodicity of about 0.5μm. By optimizing the growth conditions, uniform array of hexagonal pillar structures consisting of vertical {110} facets was successfully grown on the masked substrates, which can be used as 2DPC. Similar array of hexagonal InGaAs pillars was also grown on (111)B InP masked substrates, and was found to exhibit high optical qualify suitable for 2DPCs using InP-based materials. In addition, by growing a masked substrate with hexagonal SiO_2 masks arranged to form triangular lattice, we succeeded in the growth of GaAs 2DPC structures with hexagonal air-hole arrays when the growth conditions were optimized to suppress lateral overgrowth. Furthermore, by growing air-hole type 2DPCs on AlGaAs (111)B surfaces and selective undercut etching of AlGaAs, 2DPC slab was also successfully fabricated. Finally, Photonic bands of 2DPCs consisting of hexagonal air-hole arrays or hexagonal dielectric rods were also calculated by using plane-wave expansion method, and they were compared with those consisting of conventional circular air-holes or circular rods. Although the overall features of the photonic bands quite looked alike, the discrepancy originating from the shape of air-holes and rods were found. Especially in hexagonal air-hole arrays in orthogonal-type triangular lattice, the enhancement of overlap between TM and TE gap demonstrated, which is effective to realize 2D full photonic bandgap.