InGaAsP/InP QW impurity free intermixing for variable ZrO2 cap thickness

Impurity Free Quantum Well Intermixing (IFQWI) by cap layer thickness variation for InGaAsP/InP multiquantum wells (MQWs) is reported for the first time. The blue-shift is observed to be enhanced or inhibited depending on the thickness of the ZrO₂ cap layer used (100-600nm) for anneal conditions of 600-750°C for 40s. The group-V intermixing in InGaAsP/InP dominates the IFQWI resulting in a blue-shift of the MQW band gap and the blue-shift increases with increasing ZrO₂ thickness to 400nm. A 600nm ZrO₂ cap is found to inhibit the blue-shift. For higher anneal temperatures similar inhibition nature is observed, with larger blue-shifts. An inter-diffusion model shows that the diffusion length ratio for Group-V to Group-III initially increases from 1.25-1.6 for 100-400nm ZrO₂ thickness, but decreases to 1.1 for 600nm ZrO₂. This technique is promising for the fabrication of tapered waveguides for photonic integration of InGaAsP/InP by IFQWI.