LASER PROCESSING OF OPTOELECTRONIC MATERIALS AND DEVICES

Abstract

Optoelectronic devices are traditionally fabricated using 'wet' processes. Recently the attention has focused on 'dry', mask less techniques, of which laser material processing is one. This project investigates laser-induced etching of the GaAs/AlGaAs material system in ambient CCl2F2 and CCl4 with a view to fabricating a typical optoelectronic device such u the ridge waveguide laser diode. As the etching mechanism is expected to be largely pyrolytic, an understanding of the local temperature rise due to laser irradiation is essential. To this end, the three-dimensional heat equation was solved so that the temperature profile may be calculated. While this is straightforward in the case of GaAs, it is not so for AlGaAs because of the unavailability of crucial data such as the thermal conductivity and diffusivity. With some simplifications, an estimate of the temperature profile for AlGaAs was obtained. Etching experiments conducted suggests that lines of the required surface morphology can be obtained. However, the cross-section of the lines tend to be gaussian-shaped rather than the desired steep, vertical sidewalls. It was also found that etching of AlGaAs should be done with CCl4 or with CCl2F2 at low pressures to prevent unwanted deposition from taking place. The experimental results also highlight the inherent difficulty in obtaining consistent etch characteristics. This is attributable to the limits imposed by the equipment used.