Formation of Photonic Crystals by Selective Area Growth and Their Applications

我们发展了一种通过选区金属有机气相外延(SA-MOVPE)生长二维晶体(2DPC)的技术，形成了由六角柱和气孔结构组成的二维周期阵列。首先，在部分覆盖SiO_2掩膜的(111)B GaAs衬底上进行了GaAs和AlGaAs的SA-MOVPE。掩模图形的圆形或六角形开口阵列可实现周期约为0.5μm的三角形晶格。通过优化生长条件，成功地在掩模衬底上生长了由垂直{110}面组成的均匀阵列的六角柱结构，可用作2DPC。在(111)B InP掩模衬底上也生长了类似的六方InGaAs柱阵列，发现其具有很高的光学质量，适合于使用InP基材料的2DPC。此外，通过在掩模衬底上生长六方SiO_2掩模形成三角形晶格，在优化生长条件以抑制横向过生长的情况下，我们成功地生长了具有六方气孔阵列的GaAs2DPC结构。此外，通过在AlGaAs(111)B表面上生长气孔型2DPC和对AlGaAs进行选择性底刻刻蚀，还成功地制备了2DPC平板。最后，用平面波展开法计算了由六角形空气孔阵列和六角形介质棒组成的二维光子晶体的光子带，并与传统的圆形空气孔和圆棒组成的二维光子晶体的光子带进行了比较。虽然光子带的整体特征看起来很相似，但发现了源于气孔和棒的形状的差异。特别是在正交型三角晶格的六边形气孔阵列中，TM和TE禁带的重叠性增强，是实现二维全光子带隙的有效手段。

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.