PACS 78.67.Hc We investigate the emission from a single self-organised InAs/GaAs quantum dots as a potential single or pair photon source. Single photon emission is stimulated by exciting the dot with ps laser pulses and collecting either the exciton or biexciton emission line. A more convenient and practical arrangement is to excite the quantum dot electrically by growing it inside a p -i -n structure. Photon pairs are generated through collecting both the exciton and biexciton emissions. We show a strong correlation in the emission times of the exciton and biexciton photon from the dot, as well as in their linear polarisations.1 Introduction Single photon sources are a building block for many experiments in quantum optics, as well as photonic implementations of quantum computing [1, 2] and communication [3]. In quantum cryptography, for instance, a cryptographic key can be formed between two parties using bits encoded upon single photons transmitted along an optical fibre or through free space. By using single photons the sender and intended recipient are able to guarantee the security of their key, since quantum mechanics dictates that measurement by a third party will inevitably produce a detectable change to the encoded single photons. The secrecy of the key is difficult to achieve when using a weak pulsed laser diode, because of the unavoidable multi-photon pulses [4]. Thus the development of a true single photon source is vital for unconditional security of quantum cryptography.The first proposal to create a quantum light source was based upon the resonance fluorescence of a single two-level atom, using the fact that the emission of a photon returns the atom to its ground state, after which it must be re-excited before a second photon can be emitted [5]. This was first demonstrated experimentally in the resonance fluorescence of a low-density vapour of Na atoms [6], although the behaviour was complicated by the fact that the emission of a single atom could not be isolated. Later experiments on a single trapped Mg + ion showed a more ideal demonstration of anti-bunching [7]. In recent years, the photon emission statistics of a wide range of other quantised, two level systems have been studied, such as single molecules, CdSe/ZnS nanocrystals and nitrogen vacancy centres in diamond, see Ref.[8] for a list of references.A quantum dot is often described as the semiconductor analogue of an atom, since the three dimensional confinement of the electrons results in their energy spectrum consisting of a series of discrete lines. Each of these levels can accommodate just two electrons of different spin, due to the Pauli exclusion principle. It was proposed that a quantum dot formed by etching a lithographically defined pillar in a heterojunction could be used to make a device for emitting single photons [9]. However, the small