High-In-content InGaAs quantum point contacts fabricated using focused ion beam system equipped with N sub(2) gas field ion source

Quantum point contacts (QPCs) in high-In-content InGaAs modulation-doped heterostructures fabricated using a focused ion beam (FIB) system equipped with a N sub(2) gas field ion source (GFIS) are demonstrated. The minimum physical size of the fabricated QPCs in this study is ~30 nm, which is smaller than the typical physical size of QPCs (>50 nm) obtained by electron beam lithography and etching techniques. In addition, the fabricated QPCs are characterized electrically at low temperatures with magnetic fields. Since some of them show conductance quantization behaviors, the results indicate that the GFIS-FIB process is promising for quantum device fabrication.