480508 Determining Elastic-Plastic Deformation Limits on GaAs Using Spherical Indentation
Quantum confinement in wide band gap semiconductors has been established for heterostructure quantum well devices. A new approach for creating lateral quantum confinement in all directions using heterostructure devices is currently being explored. The technique is called press and print quantum dot fabrication. The substrate is a InGaAs quantum well deposited on GaAs using molecular beam epitaxy. The substrate is then pressed against a Si nanopillar indenter array using a custom mechanical press. It is then annealed at high temperatures, during which, in the areas where the pillars are loaded, Inidum is selectively diffused away from the InGaAs quantum well. Upon unloading the sample, GaAs quantum dots are expected to form. A significant challenge is determining the elastic-plastic deformation limits for this experiment. It is known that GaAs deforms due to the generation and propagation of line defects. During the loading event, the sheer stress applied to the substrate causes plastic deformation and propagation of line defects at very small ranges of contact pressure. Because of pronounced line defects there is electron entrapment in forbidden energy states, which causes competition between Shockley-Read-Hall and Radiative recombination events. To minimize defects caused by plastic deformation, also called pop-in events, an appropriate contact mechanics model must be used. Using the Hertzian contact model, which considers the indenter and substrate mechanical properties, we can predict pop-in events that will occur due to a material yielding upon load contact. This is often described as the onset of plasticity. The model considers GaAs as the substrate and a spherical Si indenter tip. A spherical indenter applies a more uniform stress field when compared to other indenter shapes and can extend the elastic-plastic deformation limits of the substrate. The goal is to find the onset of elastic and elastic-plastic deformation of GaAs to a Si spherical indenter. It would then be possible to find the average sheer stress value before a GaAs pop-in event.
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