Effects of heat-up procedure and grating depth on the erosion of InGaAs grating

New DFB grating structure using dopant-induced refractive index step

“…Today, this is the preferred method of grating construction and is practiced by several manufacturers. For successful overgrowth the growth initiation is critical [6,7]. For small metalorganic chemical vapour deposition (MOCVD) reactors where the heat-up time is short, the grating overgrowth works relatively well.…”

“…With a multi-wafer reactor, however, the heat-up time is substantially longer and the grating overgrowth process is therefore more challenging. The primary problem is that the exposed crystal structure is difficult to preserve during heat-up because it is a mixture of InP and InGaAsP [6]. One way to circumvent this issue is by only utilising InP and obtaining the change in index of refraction by using modulation doping along the grating period.…”