A report describes experiments that generated evidence of thermodynamic instability of nanometer-size islands (quantum dots) in InxGa1–xAs grown on GaAs. InxGa1–xAs/GaAs specimens were grown by metal-organic chemical vapor deposition, using various partial pressures of AsH3. Examination of specimens by force microscopy, electron microscopy, and low-temperature photoluminescence spectroscopy revealed differences in island formation at different partial pressures of AsH3, including differences in (1) surface coverages of islands, (2) ratios between numbers of coherent and incoherent islands, (3) sizes and shapes of islands after annealing, and (4) thicknesses for the onset of the Stranski-Krastanow (S-K) transformation (in which quantum dots form spontaneously in a second semiconductor deposited on a lattice-mismatched first semiconductor once the second semiconductor reaches a critical thickness, which is typically a few molecular layers).
This work was done by Rosa Leon of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Island Shape Instabilities and Surfactant-Like Effects in the Growth of InGaAs/GaAs Quantum Dots," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Physical Sciences category. NPO-20696
This Brief includes a Technical Support Package (TSP).
Thermodynamic Instability of InxGa1 xAs/GaAs Quantum Dots
(reference NPO-20696) is currently available for download from the TSP library.
Don't have an account?
Overview
The document presents a technical report on the thermodynamic instability of InxGa1-xAs/GaAs quantum dots, focusing on the effects of growth conditions, particularly the partial pressures of arsine (AsH3), on the formation and stability of these nanostructures. Conducted at the Jet Propulsion Laboratory (JPL) under a contract with NASA, the research aims to understand the reasons behind varying surface coverages of quantum dots produced under different conditions.
Key findings indicate that the stability of InGaAs/GaAs quantum dots is influenced by the growth environment, specifically the arsine partial pressures used during the metallorganic vapor chemical deposition (MOCVD) process. The study provides evidence for the first time that arsine can act as an impurity-free surfactant, enhancing surface energies when used above certain threshold levels. This discovery is significant as it offers insights into optimizing growth conditions to achieve desired quantum dot characteristics.
The report outlines a comprehensive experimental approach, including structural examinations of the quantum dots before and after prolonged in-situ annealing within the MOCVD chamber. The experiments aimed to correlate the growth conditions with the resulting structural properties of the quantum dots, particularly focusing on the transition from two-dimensional to three-dimensional growth, known as the Stranski-Krastanow (SK) transition.
The document emphasizes the novelty of the findings, which contribute to a deeper understanding of the thermodynamic principles governing quantum dot formation. It discusses the implications of these results for future semiconductor applications, particularly in the fields of optoelectronics and quantum computing, where the precise control of nanostructure properties is crucial.
Additionally, the report includes disclaimers regarding the endorsement of specific products or processes and clarifies that the information provided does not constitute any warranty or representation by the United States Government or NASA. The research was supported by the Australian Research Council and conducted in collaboration with the Australian National University.
In summary, this document serves as a technical support package detailing groundbreaking research on the thermodynamic stability of quantum dots, highlighting the importance of growth conditions in determining their structural properties and potential applications in advanced technologies.
