Individual GaAs quantum emitters grown by droplet epitaxy on Ge and SiGe substrates

The integration of III-V nanostructured active layers on silicon could open interesting perspectives for implementation of high performance devices for optoelectronics, photonics and quantum information technology within CMOS circuits [1]. Nanostructures based on III-V semiconductor materials have better optical properties compared to Si, and their use has largely improved optoelectronic devices performances, such as semiconductor laser. Even more striking is the possibility to exploit quantum dots with three-dimensional quantum confinement and deltalike density of states for quantum devices such as single photon [2] or entangled photon pairs emitters [3]. In this presentation, we explore the growth and optical characterization of high quality and low density GaAs quantum dots grown by droplet epitaxy [4] on Ge substrates and the possibility to integrate the same nanostructures on Si through Ge virtual substrates [5]. The adoption of droplet epitaxy method is of utter importance for our target. Droplet epitaxy is intrinsically a low thermal budget growth, being performed at temperatures between 200 and 350 °C. This makes droplet epitaxy perfectly suited for the realization of growth procedures compatible with back-end integration of III-V nanostructures on CMOS emitters. The control of the growth kinetics permitted the fabrication of quantum dot samples with extremely low areal densities (down to few 108cm -2). Single quantum dot spectroscopic characterization has been performed, by means of a micro-photoluminescence apparatus, without the need of further sample processing. Optical quality of the GaAs quantum dots is almost comparable with quantum dots directly grown on GaAs substrates, clearly demonstrating with such achievement, a new procedure for the integration of high efficient light emitters, based on III- V semiconductors, directly on IV semiconductor substrates, and opening the route to wide applications to optoelectronics, photonics and quantum information technology. [1] S. Bietti, C. Somaschini, S. Sanguinetti, N. Koguchi, G. Isella, and D. Chrastina, Applied Physics Letters 95, 241102 (2009). [2] T. Kuroda, M. Abbarchi, T. Mano, K. Watanabe, M. Yamagiwa, K. Kuroda, K. Sakoda, G. Kido, N. Koguchi, C. Mastrandrea, L. Cavigli, M. Gurioli, Y. Ogawa, and F. Minami, , Applied Physics Express 1 042001(2008) [3] A. Dousse, J. Suffczynski, Alexios Beveratos, Olivier Krebs, Aristide Lemaıtre, Isabelle Sagnes, Jacqueline Bloch, Paul Voisin, and Pascale Senellart, Nature (London) 466, 217 (2010) [4] N. Koguchi, S. Takahashi, T. Chikyow, J. Crystal Growth 111 (1991) 688. [5] J. Osmond, G. Isella, D. Chrastina, R. Kaufmann, M. Acciarri, and H. von Kaenel, Applied Physics Letters 94, 201106 (2009).