Post-deposition annealing effects on the insulator/semiconductor interfaces of Al 2 O 3 /AlGaN/GaN structures on Si substrates

The effects of post-deposition annealing (PDA) on Al 2 O 3 /AlGaN interfaces fabricated by atomic layer deposition (ALD) are studied by x-ray photoelectron spectroscopy (XPS) using synchrotron radiation. Current–voltage ( I – V ) measurements of annealed Al 2 O 3 /AlGaN/GaN metal–insulator–semiconductor (MIS)-type high electron mobility transistors (HEMTs) on Si substrates are also performed to investigate the effects of PDA. XPS results show that the amount of Al-O bonding in the Al 2 O 3 layer and Ga-O bonding in the AlGaN layer changes considerably at a PDA temperature of 600 °C. The results of the I – V measurements show that the electrical characteristics of the MIS-HEMTs change substantially at a PDA temperature of 700 °C. After PDA at 700 °C, the dynamic threshold voltage shift (Δ V th ) was reduced from 5 to 0.5 V with an increase of the gate leakage current ( I g ) from 1 × 10 −7 to 7 × 10 −5 mA mm −1 . These results indicate that the deep electron traps, such as oxide traps near the Al 2 O 3 /AlGaN interfaces, almost disappear at approximately 700 °C with the crystallization of the Al 2 O 3 layers.