GaAs single photon emitters by droplet epitaxy on Silicon

Physical properties of nanostructures are strongly influenced by their dimensions and shapes, so only a precise control on the nanocrystals morphology can allow for the fine tuning of their electronic properties. The Droplet Epitaxy (DE)[1,2] is intrinsically a low thermal budget growth, being performed at temperatures between 200 and 350 °C and is a flexible growth method, based on the sequential supply of III-column and V-column elements, which permits the fabrication of a large variety of different structures such as quantum dots (QDs), quantum rings (QRs)[3,4] and concentric quantum double rings (CQDRs)[4]. In this presentation we show the possibility to tune GaAs QDs nanostructures to act as single quantum emitters on Si substrates. The integration of III-V nanostructures on silicon would open the possibility to pursue integration between high performance quantum photonic devices and quantum information technology devices based on CMOS circuitry on Si. Low thermal budget of droplet epitaxy technique is perfectly suited for the realization of growth procedures compatible with back-end integration of III-V nanostructures on CMOS [5]. The control of the growth kinetics allows the fabrication of quantum dot samples with an areal density down to few 108 cm-2. Bright and sharp emission lines are observed in a micro-photoluminescence experiment around 700 nm, with pure radiative excitonic lifetime and clear evidence of exciton-biexciton cascade. The achievement of quantum photon statistics is directly proved by antibunching in the second order correlation function as measured with a Hanbury Brown and Twiss interferometer up to T=80 K, thus making the single photon emitter working at liquid nitrogen temperature and compatible with present CMOS technology. Optical quality of the GaAs quantum dots grown on Si substrate is almost comparable with quantum dots directly grown on GaAs substrates, clearly demonstrating a new procedure for the integration of high efficient light emitters, based on III-V semiconductors, directly on Si substrates, and opening the route to wide applications to optoelectronics, photonics and quantum information technology.[1] N. Koguchi, S. Takahashi, T. Chikyow, J. Crystal Growth 111 (1991) 688. [2] N. Koguchi and K. Ishige, Jpn. J. Appl. Phys. 32 (1993) 2052-2058. [3] K. Watanabe, N. Koguchi and Y. Gotoh, Jpn. J. Appl. Phys. 39 (2000) L79. [4] T. Mano et al, Nano Letters 5, 3, 425-428 (2005). [5] S. Bietti, C. Somaschini, S. Sanguinetti, N. Koguchi, G. Isella, and D. Chrastina, Appl. Phys. Lett. 95, 241102 (2009) [6] Cavigli L., Abbarchi M., Bietti S., Somaschini C., Sanguinetti S., Koguchi N., Vinattieri A., et al. App. Phys. Lett., 98(10), 103104 (2011)