Fermi-level unpinning on GaAs (111)A surface with direct ALD Al2O3
Although high-performance inversion-mode InGaAs NMOSFETs are demonstrated<sup>1–6</sup>, highperformance GaAs MOSFETs with directly deposited high-k dielectrics remain a big challenge. Some researchers believe that Fermi-level of GaAs is intrinsically pinned at the mid-gap with directly deposited ALD Al<inf>2</inf>O<inf>3</inf>. In this paper, we systematically study the electrical properties of ALD Al<inf>2</inf>O<inf>3</inf> NMOSCAPs, PMOSCAPs, NMOSFETs and PMOSFETs on GaAs (111)A and use (100) as a reference. (111)A is a pure Ga polar surface instead of (100) Ga-As unpolar surface. The results obtained on GaAs (111)A surface are astonishingly different from those on GaAs (100) surface. Multi-probe investigations confirm that Fermi-level of GaAs is unpinned with direct ALD Al<inf>2</inf>O<inf>3</inf>.