A novel technique for quantum-well intermixing has been developed using sputtered silica. The technique relies on the generation of point defects via plasma induced damage during the deposition of the sputtered silica. The presence of the defects before annealing allows the intermixing to take place at lower annealing temperatures (>200 C) than those needed for conventional impurity free vacancy disordering. The low annealing temperature has allowed the technique to be applied to InP based quantum well systems such as InGaAs/InGaAsP and InGaAs/InGaAlAs, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices operating around 1550 nm.
Wavelength tuned broad area oxide stripe lasers have been demonstrated in InGaAs-InAlGaAs and InGaAs-InGaAsP quantum wells. Oxide stripe lasers with integrated intermixed slab waveguides have enabled the production of a narrow (3 degrees), single lobed far field pattern in InGaAs-InAlGaAs devices. Extended cavity ridge waveguide lasers operating around 1550 nm have been demonstrated with low loss (alpha = 4.1/cm) waveguides, the loss beinglimited by free carrier absorption in the waveguide cladding layers. Ridge waveguide, deeply etched surface grating DBR lasers were fabricated both with and without intermixing the grating section. Measurements show that a significant improvement in performance is obtained from the DBR lasers when the grating section is intermixed.
The intermixing technique has been further developed in order to realise 3 bandgaps on a chip in a single annealing step for the integration of amplifiers, passive waveguides and bandgap tuned electro-absorption modulators. Modulation depths of 25 dB were measured from the modulators.
The results illustrate that the technique can routinely be used to fabricate low-loss optical interconnects and bandgap tuned devices, offering a very promising route toward photonic integration.