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Conformal growth of high-quality lateral III-V LEDS on silicon by hydride and metalorganic vapor phase epitaxy

Deliverables

The HVPE epitaxy technique involves chloride molecules as growth precursors which nucleate on monocristalline semiconductor surfaces rather than on dielectric Si-related surfaces. HVPE appears then as the preferential tool for achieving selective epitaxy applications as total freedom is left for the design of the masks. The HVPE growth is a near equilibrium growth method which is mainly limited by the kinetics of surface processes, that is by the growth anisotropy as a function of the exposed (growing) surfaces of the crystal. HVPE is thus supposed, if mastered, to be a powerful tool for the control of crystal morphologies. LASMEA has been successful in stabilising reproducible morphological profiles (beam-like shape, pyramid-like shape) on sub-micrometer or micrometer scales by selective growth on GaAs (001), (110) and {111} substrates as a function of experimental parameters (growth temperature, composition of the vapour phase) of which influence was clearly determined and modelled. Applications involve the fabrication of new structures with controlled morphologies such as alternate periodic layers for non linear optics applications, mesa networks for Photonic Bandgap applications, quantum wire arrays on top of morphologically controlled mesas.
Conformal layers with different compositions and growth conditions have been characterized using . This characterization provides a full overview of the properties of the layers in view of their application to devices. The main properties studied were related to the quality of the layers in structural and defect content terms. The conformal layers have shown a very improved quality in relation to the conventional GaAs/Si layers, they appear as nearly defect free, which open for the first time the possibility to prepare minority carrier devices based on these layers. Selective doping has been demonstrated, enabling the fabrication of diodes. Lateral heterostructures with well defined composition and sequences have been also demonstrated using these characterizations.

Exploitable results

A range of precursors for the selective area and conformal deposition and doping of GaAs / AlGaAs and related semiconductor alloys were investigated. The highest potential sources were identified, isolated and purified using techniques perfected on the project. Monitoring of their quality was performed using analytical techniques also developed on the project to ensure the highest specification products were supplied. Production of these new precursors may now proceed on a commercial basis to allow the fabrication of state of the art devices using the selective or conformal MOVPE technique.