Leakage current in single electron device due to implanted gallium dopants by focus ion beam

Abstract

Focus ion beam (FIB) technology has been employed to fabricate quantum dot based devices such as the single electron transistor (SET) on a silicon substrate with Cr/Au/Al2O3 film stack. It was discovered that the dwell time of FIB gallium beam on an area impacted the dosage of gallium ions implanted into the insulating substrate, creating a highly doped region which could lead to device leakage current. This work focus on the potential electron transport possible when an over-dosed gallium rich Al2O3 layer will lead to leakage current between otherwise electrically isolated contact pads. Using the Keithley 4200 semiconductor parametric analyzer (SPA) and the energy dispersive X-ray spectrometer (EDS) analysis; we demonstrate the detrimental effect of leakage current in the range of pA, observed between drain/source electrodes due to the high dose of gallium implanted into the insulating Al2O3. The optimized FIB etching parameters to produce a high quality of device functionality with no leakage current is also demonstrated.