| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Friday Sessions |
| Session EM+AS+EN+NS-FrM |
| Session: | Nanoparticles for Electronics and Photonics |
| Presenter: | Davide Del Gaudio, University of Michigan, Ann Arbor |
| Authors: | D. Del Gaudio, University of Michigan, Ann Arbor S. Huang, University of Michigan, Ann Arbor L. Aagesen, University of Michigan, Ann Arbor K. Thornton, University of Michigan, Ann Arbor R.S. Goldman, University of Michigan, Ann Arbor |
| Correspondent: | Click to Email |
Controlled lateral ordering of self-assembled semiconductor quantum dots (QDs) is desirable for a wide range of solid-state applications, including solar cells, lasers, and telecom devices. To date, lateral alignment of QDs has been demonstrated for multilayers of QDs.[1]
In these cases, the first layer of QDs is isotropically distributed; subsequently, during the growth of QD stacks, the accumulation of anisotropic strain often results in lateral QD alignment. However, a significant remaining question concerns the direct influence of spontaneous surface patterning on the selective nucleation of QDs.
In this work, we use a combined experimental-computational approach to directly examine correlations between buffer surface morphology and QD nucleation. For this purpose, we exploit a surface instability induced by the anisotropy of the surface diffusion constant of ad-atoms (the Ehrlich-Schwöbel effect[2]) which leads to the formation of elongated ripples, often termed “mounds”. For epitaxial growth of InAs QDs on GaAs, Ye et al. reported a preference for in-plane QD alignment along the mound lengths[1]. Here, our one-dimensional phase-field model reveals a preference for QD nucleation in regions of positive curvature,[3] such as on the sides of the mounds and/or in the “valleys” between the mounds. In our experiments, we explore the formation of InAs QDs on AlGaAs mounds using various substrate temperatures and indium exposure times.
We explore the use of fixed geometry indium evaporation as an approach to restrict QD nucleation to one side of the AlGaAs mounds, resulting in the formation of 1D QD chains.[4] Specifically, for substrate temperature of 580°C, a high density of AlGaAs mounds is observed along [0-11]. For 3 monolayer (ML) of InAs deposition, we achieved selective positioning of QDs, with an average diameter of 16nm, on one side of the mounds.
We will discuss the influence of the As species (As2 vs As4) and growth interrupts on the size, density, and spatial arrangement of QDs. We will also present a detailed analysis of the surface instabilities that induce ripple formation, and the As adsorption kinetics, which lead to the anisotropic nucleation.
References
[1] W. Ye, S. Hanson, M. Reason, X. Weng, and R. S. Goldman. (2005). J. Vac. Sci. Technol. B 23, 1736-1740.
[2] Schwöbel, R. L., & Shipsey, E. J. (1966). J. App. Phys., 37(10), 3682–3686.
[3] Seol, D. J., Hu, S. Y., Liu, Z. K., Chen, L. Q., Kim, S. G., & Oh, K. H. (2005) J. Appl. Phys., 98(4), 044910.
[4] Arciprete, F., Placidi, E., Magri, R., Del Gaudio, D., Patella, F. (2013) J. Mat. Res.28(23), 3201–3209