Toward long wavelength low density InAs/GaAs quantum dots

Abstract

Optical and morphological properties of solid source molecular beam epitaxy (MBE) grown InAs/GaAs quantum dots are investigated by photoluminescence spectroscopy (PL) and atomic force microscopy (AFM) as a function of the growth rate. The 10 K relatively high excitation density PL spectra of the investigated samples reveal the existence of multipeaks characterizing fundamental states and corresponding excited states. The emission energies are red-shifted by approximately 70 meV, when the InAs deposition rate is reduced from 0.069 ML/s to 0.013 ML/s. By further reducing the growth rate down to 0.003 ML/s an unexpected blue shift of the emission energy occurs. AFM observations, carried out on similar uncapped samples, show a monotonic decrease of the QDs density with decreasing QDs material's deposition rate. For a growth rate of 0.003 ML/s, islands density of 4.9 × 10 9 cm −2 has been achieved with a room temperature PL full width at half maximum (FWHM) of 22 meV. For the later growth rate, the blue shift of the emission energy has been correlated with desorption of In atoms during InAs deposition.