Experimental evidence of the existence of multiple charged states at Al₂O₃/GaN interfaces

Abstract

The electrical properties of metal-oxide-semiconductor (MOS) capacitors with Al 2 O 3 /GaN interfaces formed by atomic layer deposition at various deposition temperatures (T d ) were systematically investigated through comparison with the interface properties of a Si MOS capacitor. Although interface trap densities (D it ) for the GaN MOS capacitors are almost the same as for the Si MOS capacitor, surface potential fluctuation (σ s ) for the GaN MOS capacitors formed at various T d are much larger than for the Si MOS capacitor. Comparison between a theoretical calculation related to σ s and the measured results clarified that the energy dependences of σ s in the bandgap of GaN cannot be explained by electron trapping to the interface traps with the single acceptor nature (0/−). We found that the result is experimental evidence of the existence of multiple charge states at the Al 2 O 3 /GaN interfaces. The existence of multiple charge states suggests that it may be difficult to obtain good carrier transport in future GaN devices with a MOS structure.

Investigation on the interface trap characteristics in a p-channel GaN MOSFET through temperature-dependent subthreshold slope analysis

“…Table 1 summarizes the reported D it values at the Al 2 O 3 /p-GaN interface [22,[29][30][31]. The D it in this work are comparable to the reported ones at the Al 2 O 3 /p-GaN interface [22,[29][30][31], and obviously higher than those at the Al 2 O 3 /n-GaN interface [32,33]. To reduce the dielectric interface trap density and thereby improve the device performance, the growth/deposition techniques of the p-GaN and the dielectric should be optimized and their material quality should be improved.…”