The formation and optical properties of InGaAs quantum dots on exact and 2 degrees off (100) GaAs substrates

Abstract

The formation and optical properties of self-assembled InGaAs quantum dots (QDs) grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) on exact (100) and 2 degrees off (100) GaAs substrates tilted toward < 010 > direction as a function of growth interruption time (0 similar to 1200 sec) were investigated by atomic force microscopy (AFM) and photoluminescence (PL). The dots on exact (100) substrate are randomly distributed, whereas the dots on 2 degrees off (100) substrate are aligned along multiatomic steps. As the interruption time is increased, the density of dots on exact (100) substrate is decreased while their size is progressively increased, which indicate a regular Ostwald ripening process. In contrast, the average size of dots on 2 degrees off (100) substrate are saturated for the interruption time over 600 sec and in this case shows an obvious suppression of the ripening. In particular, the size of dot on 2 degrees off (100) substrate is limited within atomic terrace width (similar to 55 nm). Also, the PL peak position of QD is shifted toward higher energy by reduced confinement potential with increasing interruption time. When the dots are formed on 2 degrees off (100) GaAs substrate, the full width at half maximum (FWHM) of dot luminescence is decreased with increasing interruption time. This means that the size dispersion is reduced at longer interruption time.