Enhanced bandgap blue-shift in InGaAsP multiple-quantum-well laser structures by low-temperature-grown InP

Quantum well intermixing (QWI) in an InGaAsP multiple-quantum-well (MQW) laser structure is demonstrated using an InP epitaxial layer grown at 300 °C, by gas source molecular beam epitaxy, followed by rapid thermal annealing. Photoluminescence is used to compare the magnitude of the QWI process between low-temperature (LT)- and normal-temperature (NT, 470 °C)-grown InP layers as a function of both anneal temperature and time. For example, after an anneal at 780 °C, a large bandgap blue-shift of ~197 nm is observed in MQW structures capped with LT-InP as compared to an ~35 nm shift in identical structures capped with NT-InP. Also, the effect of the LT-InP capping is compared to NT-InP, capped with a dielectric (~100 nm of SiO2), following anneal at 800 °C for 60 s. This shows blue-shifts of ~243 and ~142 nm, respectively.