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

Abstract

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.

In Situ H-Radical Surface Treatment on Aluminum Gallium Nitride for High-Performance Aluminum Gallium Nitride/Gallium Nitride MIS-HEMTs Fabrication

“…In addition, from Equations (2) and (3), it can be seen that by changing , traps with a wider energy band range can be detected. In Figure 3 , we extracted when the capacitance reached 110% of the first plateau capacitance [ 18 ], and we marked the shift of at 50 kHz for different temperatures to demonstrate the temperature dispersions. Obviously, the frequency dispersion and the temperature dispersion of S3 are significantly suppressed compared to that of S1 and S2.…”

“…In contrast, a small Δ of ∼0.01 V as well as a small SS of ∼65 mV dec −1 was observed for the S3. This indicates that H-radical treatment can effectively suppress interface trap related switching transients in MIS-HEMTs [ 18 , 34 , 35 ]. In addition, the threshold voltages defined at drain current of 1 μA/mm are about −14, −12 and −12 V for S1, S2, and S3, respectively, which might be related to the positive charges in the natural oxide layer or other contaminants on the surface of S1 [ 36 , 37 ].…”

“…In fact, it has been reported that the high density of border traps at the surface of GaN correlated to the content of oxygen may even reach [ 16 ]. Many studies have confirmed that exposure of AlGaN surface to air produces a layer of structurally unstable oxides, resulting unsaturated valence bonds as the main source of AlGaN surface states [ 17 , 18 , 19 ]. Additionally, it has been reported that the removal or transformation of Ga-O can greatly reduce C–V frequency dispersion and improve the device performance [ 20 , 21 ].…”