A Low Program Voltage Enabled Flash like AlGaN/GaN Stack Layered MIS-HEMTs Using Trap Assisted Technique

Abstract

In this paper, a flash like Al2O3/SiO2 stacked layer AlGaN/GaN-based metal insulator semiconductor high electron mobility transistor (MIS-HEMT) was fabricated using trap assisted technique. The MIS-HEMT showed a large positive shifting of threshold voltage (∆VTH) of 4.6 V after applying a low program voltage (VP) of 3 V, resulting in a very low threshold voltage of −0.3 V with a decent maximum drain current (IDMAX) of 575 mA mm−1. A ultraviolet-ozone (UV/O3) surface treatment was done prior to gate dielectric deposition to produce a thin gallium oxynitride (GaOXNY) layer at GaN/oxide interface, which correspondingly acts as a charge trapping layer, resulting in the reduction in VP. The capacitance-voltage (C–V) measurements revealed that the traps contributing to the significant positive shifting of VTH had a density of 5.7 × 1012 cm−2. These traps were attributed to the border or oxide defects. A significant reduction in gate leakage current (IG) of more than three orders of magnitude was found in MIS-HEMT, due to the high quality Al2O3/SiO2 stack gate dielectric layer compared to conventional HEMT. The flash like stack layered programmed MIS-HEMT exhibited a GMMAX of 123 mS mm−1, on-off ratio of 1.7 × 107, subthreshold slope of 121 mV dec−1 with a reduced gate leakage current of 7.5 × 10−9 A mm−1.