Fabrication of high quality factor photonic crystal microcavities in InAsP/InGaAsP membranes

In recent work, resonant mode linewidths of 0.10nm (correspoding to a quality factor (Q) of about 13,000) were measured in a photonic crystal (PC) defect microcavity fabricated in an InAsP/InGaAsP multi-quantum well membrane. The quality of device fabrication is of critical importance in the performacne of there devices. 

We present the results of some of the key processing steps, including inductively-coupled plasma reactive ion etching of a SiO2 mask layer and the underlying InAsP/InGaAsP membrane layer, as well as the selective undercut wet etch of a sacrificial InP layer to form the free-standing membrane. The results of the membrane etch are compared with previous work done using a chemically-assisted ion beam etch system, and a discussion of the benefits of the current approach is given.