Kinetically driven selective growth of InAs quantum dots on GaAs
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Dipartimento di Fisica, Università di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy
Ernesto Placidi
Dipartimento di Fisica, Università di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy; and Consiglio Nazionale delle Ricerche – Istituto di Struttura della materia, Via Fosso del Cavaliere 100, I-00133 Roma, Italy
Rita Magri Dipartimento di Fisica, Università di Modena e Reggio Emilia, and Centro S3 CNR-Istituto, Nanoscienze, Via Campi 213/A, 4100 Modena, Italy
Davide Del Gaudio and Fulvia Patellab)
Dipartimento di Fisica, Università di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, I-00133 Roma, Italy (Received 31 May 2013; accepted 4 September 2013)
We show that, by changing and tuning the direction of the As flux on a rippled substrate, at temperatures higher than 530 °C and high As/In flux ratio, a selective growth of InAs dots can be obtained on GaAs. This is an undisclosed effect related to the Arsenic flux in the molecular beam epitaxial growth of InAs quantum dots (QDs) on GaAs(001). This effect cannot be explained by a shadowing effect, due to the gentle slopes of the mounds (1–3°), and reveals instead that As plays a fundamental role at these growth conditions. We have developed a kinetic model, which takes into account the coupling between cations and anions, and found that the very small surface gradient in the anion flux, due to the oblique evaporation on the mounded surface, is responsible for a massive drain of cations toward the surface anion-rich areas, thus generating the selective growth of QDs.
I. INTRODUCTION
During the last decade, the growth of highly strained semiconductor heterostructures has been studied extensively, especially those systems that exhibit a Stranski–Krastanov (SK) growth mode. The SK growth mode, in fact, represents an appealing approach for obtaining defect-free self-assembled quantum dots (QDs).1 Recently, the attractive prospects of QDs have been demonstrated in the case of sophisticated applications in new generation devices such as single-photon emitters for nanophotonics and quantum computing.1–3 For these exciting applications of QDs, the major challenge to be solved is a proper control over the single-QD arrangements.1 The stochastic nature of the microscopic surface processes, and more importantly of the diffusion, leads to random nucleation and size/composition fluctuations of the QDs. Until now, advances in the ordering of QDs have been obtained by combining bottom-up and top-down methods, such as introducing ex situ processing-steps (e.g., nanopatterning, etching, lithography) before and/or after the epitaxial growth,4–6 or by multilayer stacking.7–9 a)
Address all correspondence to this author. e-mail: [email protected] b) Present address: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136. This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2013.340
However, the emission properties of such arrays are still far from the hig
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