Systematic analysis of the trapping and reliability of Al2O3/GaN MOS capacitors with different atomic layer deposition techniques

We investigate the robustness and charge trapping phenomena under positive and negative bias stress in Al 2 O 3 /n-GaN metal-oxide-semiconductor capacitors fabricated with different atomic layer deposition (ALD) techniques: (i) thermal ALD (ThALD), (ii) plasma-enhanced ALD (PEALD), and (iii) stacked-ALD, obtained by alternating the latter two. The results, obtained by means of standard I-V and pulsed-CV measurements, show that PEALD results in the best oxide robustness under positive voltage stress, while ThALD results in the lowest charge trapping. We demonstrate that stacked-ALD layers presents the best trade-off to maximize robustness and minimize charge trapping phenomena, clearing the way for application in GaN MOSFET fabrication. Additionally, we compare the performance of different in-situ plasma pre-treatments on the GaN surface, proving that the NH 3 plasma is effective for improving the device performance in terms of trapped charge and reliability. The results confirm the beneficial role of stacked ALD deposition and surface pre-treatments on the electrical stability and reliability of oxide layers.