Change of characteristics of n-GaN MOS capacitors with Hf-rich HfSiOx gate dielectrics by post-deposition annealing

Abstract

We investigated the characteristics of n-GaN/Hf0.64Si0.36Ox/Pt MOS capacitors fabricated by post-deposition annealing (PDA) at 800 °C in O2 (PDO), N2 (PDN), and 3%H2 (PDH) ambients. After PDO, the Hf0.64Si0.36Ox film was partially crystallized and had a thick interfacial layer (6.3 nm) at the n-GaN/Hf0.64Si0.36Ox interface, while the Hf0.64Si0.36Ox films after PDN and PDH maintained an amorphous structure. Furthermore, the n-GaN/Hf0.64Si0.36Ox/Pt MOS capacitors produced by PDN and PDH exhibited superior characteristics, such as a small flat-band voltage (Vfb) hysteresis of +50 mV and + 25 mV, a small Vfb shift of 0.74 V and − 0.06 V, high dielectric constants of 15.1 and 16.0, and high breakdown electric fields of 8.7 and 9.1 MV/cm, respectively. However, the PDH capacitor exhibited an order of magnitude larger Dit than the PDN capacitor, suggesting that a Ga2O3 intermediate layer at n-GaN/Hf0.64Si0.36Ox interface may be decomposed after PDH and results in significant Ga diffusion into the Hf0.64Si0.36Ox films and electrical defects generation at n-GaN/Hf0.64Si0.36Ox interface. These strongly indicate that the PDN process can produce superior Hf0.64Si0.36Ox films for use as gate dielectrics in GaN power devices.