Fermi-level unpinning on GaAs (111)A surface with direct ALD Al2O3

Although high-performance inversion-mode InGaAs NMOSFETs are demonstrated, high performance 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 AI₂O₃ In this paper, we systematically study the electrical properties of ALD AI₂O₃ NMOSCAPs, PMOSCAPs, NMOSFETs and PMOSFETs on GaAs (111)A and use (100) as a reference. (lll)A is a pure Ga polar surface instead of (100) GaAs unpolar surface. The results obtained on GaAs (lll)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 AI₂O₃.