Resolution and alignment accuracy of low-temperature <i>in situ</i> electron beam lithography for nanophotonic device fabrication

Abstract

The performance of a deterministic lithographic technology to produce a reliable and accurate fabrication of nanophotonic devices based on epitaxial quantum dots is analyzed. Directly after the selection of qualified quantum dots by low-temperature cathodoluminescence spectroscopy in a scanning electron microscope, the in situ electron beam lithography step is performed. In an optimized process flow, quantum dot positions are identified with an accuracy of 25 nm, and a nanoscale alignment accuracy of the device structures of 24 nm for the emitters and one as low as 65 nm for feature sizes is demonstrated. Such accuracies surpass the performance of previously developed optical in situ lithography techniques, making this site control of quantum dots appropriate deterministic quantum device fabrication.