Effect of cap thickness on InAs/InP quantum dots grown by droplet epitaxy in metal–organic vapor phase epitaxy

InAs quantum dots (QDs) are grown on bare InP(001) via droplet epitaxy (DE) in metal–organic vapor phase epitaxy (MOVPE). Capping layer engineering, used to control QD size and shape, is explored for DE QDs in MOVPE. The method allows for the tuning of the QD emission over a broad range of wavelengths, ranging from the O- to the L-band. The effect of varying the InP capping layer is investigated optically by macro- and micro-photoluminescence (PL, µPL) and morphologically by transmission electron microscopy (TEM). A strong 500 nm blueshift of the QD emission wavelength is observed when the capping layer is reduced from 20 to 8 nm, which is reflected by a clear size reduction of the buried QDs.