Research Abstract
Optical techniques provide a powerful means of probing fundamental electronic properties of materials in a straightforward and non-destructive manner. Sample pairs of identical composition and well layer thickness, each grown along different crystallographic axes, [100] and [111], were studied using temperature dependent photoluminescence (PL) and photoluminescence excitation (PLE). This work has focused on examination of electronic transitions associated with the PL emission from these quantum well layers using variations in temperature and excitation energy. While the [100] well can be treated theoretically with the straightforward application of the standard finite square well solutions, the [111] system requires a different approach due to the presence of an intrinsic electric field. PL spectra for the samples indicate that the dominant optical transition occurs in the InGaAs layer, as expected by the effects of carrier confinement within the thin QW. PLE spectra indicate characteristic excitation energy dependence for single quantum well systems, with the primary absorption transition in the barrier (GaAs) material. Temperature dependence of PL spectra for both quantum wells indicates a deviation from the typical temperature dependence predicted by the Varshni equation for bulk materials. Using estimated incident power densities, the magnitude of the intrinsic electric field for the [111] QW systems is estimated, using the principles and equations found in introductory texts, allowing data analysis and modeling accessible for undergraduate students.

Faculty Mentors: Uwe C. Täuber, VirginiaTech Physics Department and Jason C. Brunson, Virginia Tech Mathematics Department

Research Abstract | Full PDF Abstract
Our primary focus in this study is anomalous difusion, which can be characterized by the “walk dimension.”