Fabrication of a few-electron In0.56Ga0.44As vertical quantum dot with an Al2O3 gate insulator

For the study of spin-dependent transport in narrow-gap semiconductor nanostructures, we fabricated a few-electron quantum dot based on an In0.56Ga0.44As resonant tunneling diode structure with an Al2O3 gate insulator formed by atomic layer deposition and an air-bridge drain electrode. This gated quantum dot device allows us to control the number of electrons from zero to a few dozen without leakage problem. We describe the processing techniques and the characteristics of the low-temperature transport.