Telecom O-Band Quantum Dots fabricated by Droplet Etching

We present a growth technique for fabricating low density InAs/GaAs quantum dots capable of emitting in the telecom O-band. The method combines local droplet etching on GaAs surfaces using gallium with Stranski-Krastanov growth, initiated by InAs deposition. Quantum dots nucleate directly within nanoholes before exceeding the critical layer thickness typical of standard InAs Stranski-Krastanov growth, leading to the formation of larger, low-density quantum dots. InGaAs strain reduction layers are used to further redshift the emission into and beyond the telecom O-band. Photoluminescence spectra showing a small energy difference between ground and excited states, capacitance-voltage spectroscopy revealing low Coulomb blockade energy and atomic force microscopy analysis, all indicate that quantum dots formed within nanoholes exhibit a larger volume relative to standard quantum dots. Furthermore, quantum dots nucleated in nanoholes require less indium overall to achieve emission in the O-band and demonstrate comparable or even better full-width at half-maximum. The better homogeneity, low density and increase in size makes these QDs particularly suitable for single-photon sources in quantum communication applications.