In recent years, epitaxial growth of self-assembled quantum dots has offered a way to incorporate new properties into existing solid state devices. Although the droplet heteroepitaxy method is relatively complex, it is quite relaxed with respect to the material combinations that can be used. This offers great flexibility in the systems that can be achieved. In this paper we review the structure and composition of a number of quantum dot systems grown by the droplet heteroepitaxy method, emphasizing the insights that these experiments provide with respect to the growth process. Detailed structural and composition information has been obtained using surface X-ray diffraction analyzed by the COBRA phase retrieval method. A number of interesting phenomena have been observed: penetration of the dots into the substrate (“nano-drilling”) is often encountered; interdiffusion and intermixing already start when the group III droplets are deposited, and structure and composition may be very different from the one initially intended.
References
[1]
Tessler, N.; Medvedev, V.; Kazes, M.; Kan, S.H.; Banin, U. Efficient near-infrared polymer nanocrystat light-emitting diodes. Science 2002, 295, 1506–1508.
Biolatti, E.; Iotti, R.C.; Zanardi, P.; Rossi, F. Quantum information processing with semiconductor macroatoms. Phys. Rev. Lett 2000, 85, 5647–5650.
[4]
Hanson, R.; Awschalom, D.D. Coherent manipulation of single spins in semiconductors. Nature 2008, 453, 1043–1049.
[5]
Aroutiounian, V.; Petrosyan, S.; Khachatryan, A.; Touryan, K. Quantum dot solar cells. J. Appl. Phys 2001, 89, 2268–2271.
[6]
Gratzel, M. Photoelectrochemical cells. Nature 2001, 414, 338–344.
[7]
Robel, I.; Subramanian, V.; Kuno, M.; Kamat, P.V. Quantum dot solar cells. Harvesting light energy with CdSe nanocrystals molecularly linked to mesoscopic TiO2 films. J. Am. Chem. Soc 2006, 128, 2385–2393.
[8]
Kim, S.; Mohseni, H.; Erdtmann, M.; Michel, E.; Jelen, C.; Razeghi, M. Growth and characterization of InGaAs/InGaP quantum dots for midinfrared photoconductive detector. Appl. Phys. Lett 1998, 73, 963–965.
[9]
Lim, H.; Tsao, S.; Zhang, W.; Razeghi, M. High-performance InAs quantum-dot infrared photodetectors grown on InP substrate operating at room temperature. Appl. Phys. Lett 2007, 90, 131112:1–131112:3.
[10]
Teichert, C. Self-organization of nanostructures in semiconductor heteroepitaxy. Phys. Rep 2002, 365, 335–432.
[11]
Stangl, J.; Holy, V.; Bauer, G. Structural properties of self-organized semiconductor nanostructures. Rev. Mod. Phys 2004, 76, 725–783.
[12]
Wang, L.W.; Kim, J.N.; Zunger, A. Electronic structures of [110]-faceted self-assembled pyramidal InAs/GaAs quantum dots. Phys. Rev. B 1999, 59, 5678–5687.
[13]
Bruls, D.M.; Vugs, J.W.A.M.; Koenraad, P.M.; Salemink, H.W.M.; Wolter, J.H.; Hopkinson, M.; Skolnick, M.S.; Long, F.; Gill, S.P.A. Determination of the shape and indium distribution of low-growth-rate InAs quantum dots by cross-sectional scanning tunneling microscopy. Appl. Phys. Lett 2002, 81, 1708–1710.
[14]
Grundmann, M.; Stier, O.; Bimberg, D. InAs/GaAs pyramidal quantum dots—Strain distribution, optical phonons, and electronic-structure. Phys. Rev. B 1995, 52, 11969–11981.
[15]
Joyce, P.B.; Krzyzewski, T.J.; Bell, G.R.; Joyce, B.A.; Jones, T.S. Composition of InAs quantum dots on GaAs(001): Direct evidence for (In,Ga)As alloying. Phys. Rev. B 1998, 58, 15981–15984.
[16]
Koguchi, N.; Takahashi, S.; Chikyow, T. New MBE growth method for InSb quantum-well boxes. J. Cryst. Growth 1991, 111, 688–692.
[17]
Ro, J.R.; Kim, S.B.; Park, K.W.; Lee, E.H.; Lee, J.W. Ga-droplet-induced formation of GaAs nano-islands by chemical beam epitaxy. J. Cryst. Growth 1999, 201, 1198–1201.
[18]
Gherasimova, M.; Cui, G.; Jeon, S.R.; Ren, Z.; Martos, D.; Han, J.; He, Y.; Nurmikko, A.V. Droplet heteroepitaxy of GaN quantum dots by metal-organic chemical vapor deposition. Appl. Phys. Lett 2004, 85, 2346–2348.
[19]
Mano, T.; Watanabe, K.; Tsukamoto, S.; Fujioka, H.; Oshima, M.; Koguchi, N. New self-organized growth method for InGaAs quantum dots on GaAs(001) using droplet epitaxy. Jpn. J. Appl. Phys. 2 1999, 38, L1009–L1011.
[20]
Mano, T.; Watanabe, K.; Tsukamoto, S.; Imanaka, Y.; Takamasu, T.; Fujioka, H.; Kido, G.; Oshima, M.; Koguchi, N. InAs quantum dots growth by modified droplet epitaxy using sulfur termination. Jpn. J. Appl. Phys. 1 2000, 39, 4580–4583.
[21]
Shusterman, S.; Raizman, A.; Paltiel, Y. Narrow gap nano-dots growth by droplets heteroepitaxial mode. Infrared Phys. Technol 2009, 52, 229–234.
[22]
Mano, T.; Kuroda, T.; Sanguinetti, S.; Ochiai, T.; Tateno, T.; Kim, J.; Noda, T.; Kawabe, M.; Sakoda, K.; Kido, G.; et al. Self-assembly of concentric quantum double rings. Nano Lett 2005, 5, 425–428.
[23]
Biasiol, G.; Heun, S. Compositional mapping of semiconductor quantum dots and rings. Phys. Rep 2011, 500, 117–173.
[24]
Cohen, E.; Yochelis, S.; Westreich, O.; Shusterman, S.; Kumah, D.P.; Clarke, R.; Yacoby, Y.; Paltiel, Y. Structure of droplet-epitaxy-grown InAs/GaAs quantum dots. Appl. Phys. Lett 2011, 98, 243115:1–243115:3.
[25]
Kumah, D.P.; Shusterman, S.; Paltiel, Y.; Yacoby, Y.; Clarke, R. Atomic-scale mapping of quantum dots formed by droplet epitaxy. Nat. Nanotechnol 2009, 4, 835–838.
[26]
Shusterman, S.; Paltiel, Y.; Sher, A.; Ezersky, V.; Rosenwaks, Y. High-density nanometer-scale InSb dots formation using droplets heteroepitaxial growth by MOVPE. J. Cryst. Growth 2006, 291, 363–369.
[27]
Yacoby, Y.; Pindak, R.; MacHarrie, R.; Pfeiffer, L.; Berman, L.; Clarke, R. Direct structure determination of systems with two-dimensional periodicity. J. Phys.Condens. Mat 2000, 12, 3929–3938.
[28]
Yacoby, Y.; Sowwan, M.; Stern, E.; Cross, J.O.; Brewe, D.; Pindak, R.; Pitney, J.; Dufresne, E.M.; Clarke, R. Direct determination of epitaxial interface structure in Gd2O3 passivation of GaAs. Nat. Mater 2002, 1, 99–101.
[29]
Kumah, D.P.; Riposan, A.; Cionca, C.N.; Husseini, N.S.; Clarke, R.; Lee, J.Y.; Millunchick, J.M.; Yacoby, Y.; Schlepuetz, C.M.; Bjoerk, M.; et al. Resonant coherent Bragg rod analysis of strained epitaxial heterostructures. Appl. Phys. Lett 2008, 93, 081910:1–081910:3.
[30]
Kumah, D.P.; Wu, J.H.; Husseini, N.S.; Dasika, V.D.; Goldman, R.S.; Yacoby, Y.; Clarke, R. Correlating structure, strain, and morphology of self-assembled InAs quantum dots on GaAs. Appl. Phys. Lett 2011, 98, 021903:1–021903:3.
[31]
Wang, Z.M.; Liang, B.L.; Sablon, K.A.; Salamo, G.J. Nanoholes fabricated by self-assembled gallium nanodrill on GaAs(100). Appl. Phys. Lett 2007, 90, 113120:1–113120:3.
[32]
Harmand, J.C.; Li, L.H.; Patriarche, G.; Travers, L. GaInAs/GaAs quantum-well growth assisted by sb surfactant: Toward 1.3 μm emission. Appl. Phys. Lett 2004, 84, 3981–3983.
[33]
Peng, C.S.; Huang, Q.; Cheng, W.Q.; Zhou, J.M.; Zhang, Y.H.; Sheng, T.T.; Tung, C.H. Improvement of Ge self-organized quantum dots by use of Sb surfactant. Appl. Phys. Lett 1998, 72, 2541–2543.
Spencer, B.J.; Tersoff, J. Stresses and first-order dislocation energetics in equilibrium Stranski-Krastanow islands. Phys. Rev. B 2001, 6320, 205424:1–205424:9.
[36]
Lema？tre, A.; Patriarche, G.; Glas, F. Composition profiling of InAs/GaAs quantum dots. Appl. Phys. Lett 2004, 85, 3717–3719.
[37]
Shusterman, S.; Raizman, A.; Sher, A.; Paltiel, Y.; Schwarman, A.; Lepkifker, E.; Rosenwaks, Y. Nanoscale mapping of strain and composition in quantum dots using kelvin probe force microscopy. Nano Lett 2007, 7, 2089–2093.
[38]
Girard, P. Electrostatic force microscopy: Principles and some applications to semiconductors. Nanotechnology 2001, 12, 485–490.
