Huang Hsien-Chih, Kim Munho, Zhan Xun, Chabak Kelson, Kim Jeong Dong, Kvit Alexander, Liu Dong, Ma Zhenqiang, Zuo Jian-Min, Li Xiuling
Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States.
Department of Materials Science and Engineering, Materials Research Laboratory , University of Illinois , Urbana , Illinois 61801 , United States.
ACS Nano. 2019 Aug 27;13(8):8784-8792. doi: 10.1021/acsnano.9b01709. Epub 2019 Jun 24.
β-GaO, with a bandgap of ∼4.6-4.9 eV and readily available bulk substrates, has attracted tremendous interest in the wide bandgap semiconductor community. Producing high aspect ratio β-GaO 3D nanostructures without surface damage is crucial for next-generation power electronics. However, most wet etching methods can only achieve very limited aspect ratios, while dry etch usually damages the surface due to high energy ions. In this work, we demonstrate the formation of β-GaO fin arrays on a (010) β-GaO substrate by metal-assisted chemical etching (MacEtch) with high aspect ratio and sidewall surfaces with excellent quality. The etching was found to be strongly crystal orientation dependent, and three kinds of vertical structures were formed after MacEtch. The Schottky barrier height (SBH) between Pt and various MacEtch-produced β-GaO surfaces and sidewalls was found to decrease as the aspect ratio of the β-GaO vertical structure increased. This could be attributed to the different amount of oxygen lost at the surface after etching, as indicated by the XPS and TEM examination. Very little hysteresis was observed in the capacitance-voltage characteristics for the 3D Pt/AlO/β-GaO MOS capacitor structures, and the extracted interface trap density was as small as 2.73 × 10 cm eV, comparable to or lower than that for unetched planar β-GaO surfaces.
β-GaO₃带隙约为4.6 - 4.9 eV且具有易于获得的块状衬底，在宽带隙半导体领域引起了极大关注。制备无表面损伤的高纵横比β-GaO₃三维纳米结构对于下一代功率电子学至关重要。然而，大多数湿法蚀刻方法只能实现非常有限的纵横比，而干法蚀刻通常由于高能离子而损坏表面。在这项工作中，我们展示了通过金属辅助化学蚀刻（MacEtch）在（010）β-GaO衬底上形成具有高纵横比和高质量侧壁表面的β-GaO鳍片阵列。发现蚀刻强烈依赖于晶体取向，并且在MacEtch后形成了三种垂直结构。发现Pt与各种MacEtch制备的β-GaO表面和侧壁之间的肖特基势垒高度（SBH）随着β-GaO垂直结构的纵横比增加而降低。这可以归因于蚀刻后表面氧损失量的不同，如XPS和TEM检查所示。对于3D Pt/Al₂O₃/β-GaO MOS电容器结构，在电容-电压特性中观察到非常小的滞后现象，并且提取的界面陷阱密度低至2.73×10¹¹ cm⁻² eV⁻¹，与未蚀刻的平面β-GaO表面相当或更低。
