Comparative analysis of Y₂O₃ and Al₂O₃ interfacial layers in modulating the electrical properties of ZrO₂ and HfO₂ on Ge

Abstract This study compares the effects of ultrathin Y 2 O 3 and Al 2 O 3 interfacial layers on the electrical properties of ZrO 2 and HfO 2 dielectrics deposited on Ge substrates, specifically examining the ZrO 2 /Y 2 O 3 , ZrO 2 /Al 2 O 3 , HfO 2 /Y 2 O 3 , and HfO 2 /Al 2 O 3 stacked structures. Reductions in both interface trap density ( D it ) and leakage current were observed after five cycles of the atomic layer deposition (ALD) process for Y 2 O 3 and Al 2 O 3 interfacial layers. Compared with Y 2 O 3 , the Al 2 O 3 interfacial layer was more effective in reducing the leakage current and decreasing the effective bulk trap density ( N trap ). However, this also leads to an increase in the capacitance-equivalent oxide thickness, which could be a potential drawback. The observed electrical properties are closely linked to the distinct interfacial reactions of Y 2 O 3 and Al 2 O 3 with Ge during ALD, resulting in similar reductions in D it . However, the formation of a thick Al 2 O 3 interfacial layer was more efficient in suppressing Ge out-diffusion than Y 2 O 3 , which contributed to the reduction in both the leakage current and N trap .