Effect of surface treatment on electrical properties of GaN metal-insulator-semiconductor devices with Al₂O₃ gate dielectric

This research proposes an economical and effective method of 1-octadecanethiol (ODT) treatment on GaN surfaces prior to Al₂O₃ gate dielectric deposition. GaN-based metal-insulator-semiconductor (MIS) devices treated by HCl, O₂ plasma and ODT are demonstrated. ODT treatment was found to be capable of suppressing native oxide and also of passivating the GaN surface effectively; hence the interface quality of the device considerably improved. The interface trap density of Al₂O₃/GaN was calculated to be around 3.0 × 10¹² cm^-2 eV^-1 for devices with ODT treatment, which is a relatively low value for GaN-based MIS devices with Al₂O₃ as the gate dielectric. Moreover, there was an improvement in the gate control characteristics of MIS-HEMTs fabricated with ODT treatment.