Individual GaAs quantum emitters grown by droplet epitaxy on Si substrate

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. In this work, we present the growth and optical characterization of high quality GaAs quantum dots (as single photon emitters) grown by droplet epitaxy on Si substrates through the deposition of a thin Ge layer. Droplet epitaxy [1] 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 [2]. 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] S. Bietti, C. Somaschini, S. Sanguinetti, N. Koguchi, G. Isella, and D. Chrastina, Applied Physics Letters 95, 241102 (2009)