| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Wednesday Sessions |
| Session EN+NS-WeA |
| Session: | Nanostructures for Energy Conversion & Storage I |
| Presenter: | M.V. Warren, University of Michigan, Ann Arbor |
| Authors: | M.V. Warren, University of Michigan, Ann Arbor C. Uher, University of Michigan, Ann Arbor R.S. Goldman, University of Michigan, Ann Arbor |
| Correspondent: | Click to Email |
The controlled formation of semiconductor nanocomposites offers a unique opportunity to tailor functional materials with a variety of novel properties. In particular, nanocomposites consisting of InAs nanostructures embedded in GaAs have been proposed for high efficiency photovoltaics and high figure-of-merit thermoelectrics. A promising approach to nanocomposite synthesis is matrix-seeded growth, which involves ion-beam-amorphization of a semiconductor film, followed by nanoscale re-crystallization via annealing [1]. In earlier studies of In+ implantation into GaAs, the formation of InGaAs alloys upon annealing was reported [2-4]. Due to the large size difference between In and Ga, it is likely that phase separation occurs, especially for high indium fraction InGaAs alloys. Therefore, we are examining the possibility of selective formation of InAs-rich nanocrystals in a GaAs matrix using high dose In implantation into GaAs. However, Profile Code simulations suggest that the retained In dose in GaAs, 4.5x1020 cm-3, is limited by sputtering. To increase the concentration of implanted In, we have developed a sputter-mask method, for which a sacrificial layer with sputter yield lower than that of GaAs is used to prevent sputtering of GaAs:In. Using 100kV ions with fluences ranging from 3.8x1015 to 3.8x1017 cm-2, we have implanted In+ ions into GaAs with 50 nm sputter-masks consisting of AlAs. Following implantation, the films were annealed at 500 to 600°C for 30 to 60 s. We will discuss the influence of In+ dose and annealing conditions on the nucleation and growth of InAs, as well as the influence of nanostructuring on the temperature dependence of the resistivity and Seebeck coefficient of the implanted structures.
This work is supported in part by the GAANN Fellowship and the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center
[1] X. Weng, W. Ye, S. Clarke, A. Daniel, V. Rotberg, R. Clarke, and R.S. Goldman, J. Appl. Phys. 97, 064301 (2005).
[2] M.V. Ardyshev and V.F. Pichugin, Russian Physics Journal 47, 175 (2004).
[3] M. Kulik, F.F. Komarov, and D.D. Maczka, Vacuum 63, 755 (2001).
[4] M. Kulik, A.P. Kobzev, D. Jaworska, J. Zuk, and J. Filiks, Vacuum 81, 1124 (2007).