GaAs single photon emitters at liquid nitrogen on Silicon substrates

The integration of III-V nanostructures on silicon would allow to combine the high performance of III-V quantum photonic devices and of CMOS circuitry embedded on Si. In this work, we present the fabrication and characterization of single photon emission from high quality GaAs quantum dots (QDs) grown by droplet epitaxy (DE) [1] on Si through a thin Ge buffer layer deposited by Low Energy Plasma Enhanced Chemical Vapour Deposition (LEPECVD) [2]. In figure 1 a sketch of the sample is reported. The deposition of a thin Ge layer by LEPECVD allows for the reduction of threading dislocation density down to few 107 cm−2. DE is an intrinsically low thermal budget technique, being performed at temperatures between 200 and 350 °C. This makes DE perfectly suited for the implementation of growth procedures compliant with back-end integration of III-V nanostructures on CMOS. GaAs QDs with a density of few 108 cm−2 and a mean height of 8 nm are fabricated by DE inside a Al0.30Ga0.70As barrier. To improve the quality of the GaAs QDs, two annealing procedure with reduced thermal budget are performed. The first one in chamber right after the quantum dots deposition to desorb As excess, the second one in a rapid thermal annealing system in order to improve crystal quality. 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 [3]. 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 (figure 2), thus making the single photon emitter working at liquid nitrogen temperature and compatible with present CMOS technology. The 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 hig