Well-suppressed interface states and improved transport properties of AlGaN/GaN MIS-HEMTs with PEALD SiN gate dielectric

Abstract

SiN deposited by plasma-enhanced atomic layer deposition (PEALD) is investigated as gate dielectric layer for GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs). The X-ray photoelectron spectroscopy (XPS) confirms low oxygen content in SiN-layer and the interface of SiN/(Al)GaN. The fabricated MIS-HEMTs exhibit significant reduction in gate leakage current (two or three orders of magnitude) and improvement in drain current (ID) characteristics, compared with the controlled HEMTs. A remarkable small threshold voltage (VTH) hysteresis (0.12 ± 0.05 V) and an enhanced 2DEG channel mobility are also achieved for PEALD SiN/(Al)GaN MIS-HEMTs. Simultaneously, a distribution of the interface states is quantitatively described by constant-capacitance deep-level transient spectroscopy (CC-DLTS), displaying a low density of 1.6 × 1013 cm−2 eV−1 at level depth of 0.03 eV and below 2.1 × 1012 cm−2 eV−1 at deep level depth of EC - ET > 0.4 eV. The suppressed interface traps density results in an improved performance for MIS-HEMTs. The dependence of the characteristics of MIS-HEMTs on SiN thickness (tSiN) was also studied in detail.