Very low loss waveguides formed by fluorine induced disordering of GaInAs/GaInAsP quantum wells

Selective area intermixing of quantum well (QW) structures using fluorine as a disordering impurity is demonstrated. Bandgap widened ridge waveguides have been fabricated using this process and the resultant waveguides had losses of between 8.5 dB cm/sup -1/ and 0.6 dB cm/sup -1/. In purely thermally intermixed samples, the lowest loss measured is 18.5 dB cm/sup -1/ and, if an electrically active dopant was used as a disordering species, a propagation loss due to free-carrier absorption of greater than 40 dB cm/sup -1/ is expected. By implanting with fluorine to give a concentration of around 10/sup 18/ cm/sup -3/ and annealing at 700 degrees C it is possible to widen the QW structure by as much as 40 meV, while leaving the unimplanted structure relatively unchanged. It has also been shown that SiO/sub 2/, but not Si/sub 3/N/sub 4/, dielectric caps can be used to provide protection during the annealing stage of the process.<>