High Aspect Ratio HBr Based Dry Etching of GaInAsP/InP for Nanoscale Photonic Couplers

Large scale integrated photonics demand nanoscale features that extend deeply into the III-V substrate to cover a propagating mode. The researchers discuss HBr etching of frustrated total internal reflection (FTIR) couplers with feature sizes of approximately 140nm wide by 20 $\mu$m long by 3 $\mu$m deep in InP. A variety of HBr based chemistries will be benchmarked against more traditional Chlorine based processes. Both FIB and EBL patterned features will be presented with aspect ratios greater than 30:1. Importantly, with HBr, the hetereostructures can be etched through with reasonable smoothness at 165 degrees Celsius, and these are beneficial for reliable InP devices.