We show here that Cd(Zn)O can be deposited on GaAs by MOCVD forming nanoparticles with a hemispherical shape. These nanoparticles maintain the key characteristics from a CdO film: very high plasma frequency and very low losses, hence retaining the strong plasmonic character. As a result of this, when illuminated with infrared light, two localized surface plasmon (LSP) modes are excited at 2.7 and 5.3 microns, and the electric field is heavily amplified in the underlying GaAs substrate. Moreover, their hemispherical geometry allows them to partially change the orientation of the field, creating a component perpendicular to the surface. We prove the coupling between the CdO LSPs and the intersubband transitions from a multiple QW structure, where the absorption is largely enhanced for p-polarized electric fields, and it is observed even under normal incidence conditions.
In this work we propose the use of self-assembled CdZnO nanoparticles as a route to improve power absorption in midinfrared GaAs-based quantum well infrared photodetectors (QWIPs). We experimentally demonstrate low temperature growth of CdZnO nanoparticles on GaAs and characterize their plasmonic response in the mid-IR. Computational analysis of the plasmonic resonances coupled to intersubband transitions in GaAs quantum wells show that intersubband absorption at normal incidence, forbidden by quantum selection rules, can be obtained. Gains in the quantum well power absorption as high as 5.5 are also reported.
The unavoidable presence of the wetting layer (WL) in Stranski-Krastanov quantum dots (QD) has typically a negative impact on the performance of QD solar cells. In this work, a simple method to engineer the WL of InAs/GaAs QD solar cells is investigated. In particular, we show that covering the QDs at high GaAs capping rates reduces In-Ga intermixing and, therefore, In redistribution from the QDs to the WL. This results not only in larger QDs, but also in thinner WLs, with larger quantum confinement energies and reduced potential barriers for electrons and holes. Carrier trapping by the WLs and subsequent recombination is therefore reduced, resulting in larger photocurrent values of the QD solar cells under short circuit conditions.
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