Single InAs quantum dot (QD) sample is grown by molecular-beam epitaxy (MBE), and the photoluminescence (PL) from a single QD at 5 K is measured. By means of Hanbury-Brown and Twiss (HBT) setup, we measure the photon correlation of the PL which indicates that the PL of QD is single-photon emission. This single-photon source is used to demonstrate experimentally the single-photon interference via Mach-Zehnder (MZ) interferometer. In addition, the measured interference and fringe visibility are analyzed by changing the different linear polarization of the photon between two arms of MZ interferometer.

Molecular beam epitaxy growth of GaAs on an offcut Ge (100) substrate has been systemically investigated. A high quality GaAs/Ge interface and GaAs film on Ge have been achieved. High temperature annealing before GaAs deposition is found to be indispensable to avoid anti-phase domains. The quality of the GaAs film is found to strongly depend on the GaAs/Ge interface and the beginning of GaAs deposition. The reason why both high temperature annealing and GaAs growth temperature can affect epitaxial GaAs film quality is discussed. High quality In0.17Ga0.83As/GaAs strained quantum wells have also been achieved on a Ge substrate. Samples show flat surface morphology and narrow photoluminescence line width compared with the same structure sample grown on a GaAs substrate. These results indicate a large application potential for III—V compound semiconductor optoelectronic devices on Ge substrates.

Single InAs quantum dot (QD) sample was grown by molecular-beam epitaxy (MBE). The Photoluminescences (PL) of the exciton and biexciton in a single QD were measured at 5 K. The PL intensity as a function of the laser excitation power, the fine structure splittings of the exciton and biexciton, and the corresponding linearly polarized emissions were analyzed. By means of Hanbury-Brown and Twiss (HBT) setup, the photon correlation between the PL of exciton and biexciton were measured, which is gave an evidence of the quantum cascade emissions between biexciton and exciton PL.

By using polarization-resolved photoluminescence spectra, we study the electron spin relaxation in single InAs quantum dots (QDs) with the configuration of positively charged excitons X+ (one electron, two holes). The spin relaxation rate of the hot electrons increases with the increasing energy of exciting photons. For electrons localized in QDs the spin relaxation is induced by hyperfine interaction with the nuclei. A rapid decrease of polarization degree with increasing temperature suggests that the spin relaxation mechanisms are mainly changed from the hyperfine interaction with nuclei into an electron-hole exchange interaction.

We report on the single photon emission from single InAs/GaAs self-assembled Stranski–Krastanow quantum dots up to 80 K under pulsed and continuous wave excitations. At temperature 80 K, the second-order correlation function at zero time delay, g(2) (0), is measured to be 0.422 for pulsed excitation. At the same temperature under continuous wave excitation, the photon antibunching effect is observed. Thus, our experimental results demonstrate a promising potential application of self-assembled InAs/GaAs quantum dots in single photon emission at liquid nitrogen temperature.