∼1meV inhomogeneous broadening of large area (∼cm2) arrays of site-controlled pyramidal quantum dots

For quantum dot (QD) based devices, non-uniformity of size and shape is clearly undesirable, as the resulting structures will exhibit a broad range of electronic and optical properties, effectively smearing out the sought-after zero-dimensional behaviour of the dot ensemble. Seeded self-ordering, which involves the self-formation of nanostructures at nucleation sites introduced by a substrate patterning process, is particularly attractive because it allows for control over the site of the nano structures while maintaining high quality and uniformity of QD arrays. This paper reports on an inhomogeneous broadening in the range of 1meV for QD arrays fabricated by organo-metallic chemical vapor deposition (OMCVD) on pre-patterned substrates. Various techniques beginning with processing of pyramidal recesses to certain growth optimizations are employed to improve the homogeneity of the QDs grown into the pyramidal processes.The low temperature micro photoluminescence (muPL) spectrum of an ensemble of 8-10 dots shows energy spread of 6.15meV. For the investigation of the sample´s spatial homogeneity, sequential measurement of the muPL spectra is done of such QD ensembles strictly every 200 mum along the length of the sample, which gives a representative 400 QD subsets of the entire sample area. The single exciton, bi-exciton, and single-charged exciton emission peaks are clearly observed.