Oxide–semiconductor micro-pillar cavities

We have investigated the wet oxidation of high aluminium-content AlGaAs layers to give a stable, low refractive index, insulating aluminium oxide (AlOx), which we use to form high-index contrast Bragg mirrors. The AlOx/GaAs material combination achieves a ∼15% reflectivity at each interface and so not only are fewer mirror periods required to achieve a high reflectivity but also the penetration of light into the mirrors is reduced. Hence, a cavity bounded by these mirrors can confine photons within a very small volume, modifying the emission characteristics of a single quantum state in the cavity through the Purcell effect. Here, we present an experimental observation of a three-fold enhancement in spontaneous emission rate for a single InAs quantum dots in such a cavity.