A photon source, comprising: a semiconductor structure, said semiconductor structure comprising: a first light emitting diode region; and a second region comprising a quantum dot; the photon source further comprising: a first voltage source configured to apply an electric field across said first light emitting diode region to cause light emission; a second voltage source configured to apply a tuneable electric field across said second region to control the emission energy of said quantum dot; wherein the semiconductor structure is configured such that light emitted from said first light emitting diode region is absorbed in said second region and produces carriers to populate said quantum dot; and wherein the photon source is configured such that light emitted from the second region exits said photon source.