Water direct bonding for photonic integrated circuits

为了使激光二极管稳定工作，光隔离器是保护其免受不必要反射的必不可少的元件。为了实现光隔离器与激光二极管的集成，本文研究了磁光石榴石(LuNdBi)_3(FeAl)_5O_(12)与InP/GaInAsP晶片的直接键合，确定了包括表面处理和热处理温度在内的适宜键合条件。此外，还针对几种器件制造工艺对粘接样品的耐久性进行了研究。结果表明，在H_2气氛中，即使在110220ﾟ℃的低温下，成键也是成功的。低温处理有效地抑制了石榴石的光吸收损耗的增加。我们研究了将该技术扩展到其他材料组合的可能性。研究发现，用射频溅射方法沉积的SiO_2层可以用类似的方法键合到(100)InP衬底上。由于SiO_2层的表面粗糙，粘结样品的耐久性不足以完成完整的器件制作过程，因此开发了一种结构与器件制作工艺兼容的新型光隔离器。它由生长在InP衬底上的GaInAsP导向层组成。磁光石榴石作为上包层直接结合在GaInAsP导向层上。

An optical isolator is indispensable to protect a laser diode from unwanted reflections for its stable operation. In order to integrate the optical isolator with the laser diode, direct bonding between magnetooptic garnet like (LuNdBi)_3 (FeAl)_5O_<12> and InP/GaInAsP wafers is investigated in this study.The suitable conditions, which include the surface treatment and the temperature of heat treatment, have been found to establish the wafer bonding. The durability of bonded sample was also investigated against several device fabrication processes. It has been found that the bonding is successfully established even at low temperature ranging from 110-220ﾟC in H_2 ambient. The low temperature treatment was effective to suppress an increase in optical absorption loss of the garnet.We examined the possibility of extending the technique to other material combination. It was found that SiO_2 layr deposited by RF sputtering could be bonded to a (100) InP substrate using a similar technique. Because of the surface roughness of SiO_2 layr, the durability of the bonded sample was not sufficient to undergo the full device fabrication processes.The novel optical isolator whose structure is compatible to the device fabrication process has been exploited. It is composed of a GaInAsP guiding layr grown on an InP substrate. The magnetooptic garnet is directly bonded to the GaInAsP guiding layr as an upper cladding layr.