Structural properties of templated Ge quantum dot arrays: impact of growth and pre-pattern parameters

Abstract

In this study we analyze the impact of process and growth parameters on the structural properties of germanium (Ge) quantum dot (QD) arrays. The arrays were deposited by molecular-beam epitaxy on pre-patterned silicon (Si) substrates. Periodic arrays of pits with diameters between 120 and 20 nm and pitches ranging from 200 nm down to 40 nm were etched into the substrate prior to growth. The structural perfection of the two-dimensional QD arrays was evaluated based on SEM images. The impact of two processing steps on the directed self-assembly of Ge QD arrays is investigated. First, a thin Si buffer layer grown on a pre-patterned substrate reshapes the pre-pattern pits and determines the nucleation and initial shape of the QDs. Subsequently, the deposition parameters of the Ge define the overall shape and uniformity of the QDs. In particular, the growth temperature and the deposition rate are relevant and need to be optimized according to the design of the pre-pattern. Applying this knowledge, we are able to fabricate regular arrays of pyramid shaped QDs with dot densities up to 7.2 × 10 cm.

Ultrahigh-resolution quantum dot patterning for advanced optoelectronic devices

“…Therefore, many studies focused on the development of single particle resolution layouts of epitaxial QDs, which are needed for emerging quantum functional devices related to quantum information technologies. 67–70 Schramm et al have employed nanoimprint lithography to fabricate a GaAs template with nanometer scale patterns, on which InAs QDs are grown via MBE. Fig.…”

“…Therefore, an analogous interest in controlling the spatial relationship between the dots and fabricating QD patterns with desired resolutions and shapes has been discussed for epitaxial QDs. [65][66][67][68][69][70][71][72][73] The epitaxial QDs are fabricated by self-assembly in the Stranski-Krastanov growth mode, which is mainly achieved by the combination of semiconductor elements with a lattice mismatch of a few percent. This self-assembly principle requires a surface with nucleation site arrays to direct and confine the growth of QDs, and hence, the prerequisite of patterning epitaxial QDs is precise patterning of the template array.…”

“…Therefore, many studies focused on the development of single particle resolution layouts of epitaxial QDs, which are needed for emerging quantum functional devices related to quantum information technologies. [67][68][69][70] 8a shows the single InAs QDs grown on a structured hole pattern with a 1.5 mm period. Depending on the size and shape of the template confinement, diverse pattern arrangements such as QD lines with single particle width resolution and nanoslot patterns with anisotropic direction in relation to the substrate lattice parameters have been demonstrated by different groups (Fig.…”

Investigation of the resolution limit of Talbot lithography with compact EUV exposure tools

“…Dense periodic nanostructures with feature sizes below 100 nm are essential for numerous industrial and scientific applications, such as photoresist qualification for achieving high resolution 1,2 and the production of metamaterials, biosensors, quantum dot arrays, and artificial crystals [3][4][5] . Fabricating these nanostructures is a complex task, requiring advanced patterning technologies like electron beam lithography, nanoimprint lithography, or industrial projection lithography.…”

Towards the resolution limit of Talbot lithography with compact EUV exposure tools

“…Dense periodic nanostructures with minimal feature size below 100 nm are required and actively investigated for many industrial and scientific applications, like photoresist qualification regarding the achievable resolution 1,2 , or for the realization of metamaterials, biosensors, quantum dot arrays or artificial crystals [3][4][5] . The fabrication of these nanostructures is a challenging task and requires the utilization of advanced patterning technologies like electron beam lithography, nanoimprint lithography or industrial projection lithography.…”